Manual
RasMol 2.7.1

Molecular Graphics Visualisation Tool
22 June 1999

The original RasMol manual was created by Roger Sayle. In July 1996, Dr. Margaret Wong of the Chemistry Department, Swinburne University of Technology, Australia, made extensive revisions to the RasMol 2.5 manual to accurately reflect the operation of RasMol 2.6. Eric Martz of the University of Massachusetts made further revisions. In May 1997, William McClure of Carnegie Mellon University reorganized the HTML version of the manual into multiple sections which could be downloaded quickly and added use of frames. Portions of the 2.7.1 version of the RasMol manual were derived with permission from William McClure's version using Roger Sayle's rasmol.doc for version 2.6.4 as the primary source.

THIS IS A PRELIMINARY RELEASE INVOLVING EXTENSIVE MODIFICATIONS
***** USE WITH CAUTION ******

IMPORTANT

This version is based on RasMol version 2.6_CIF.2, on RasMol version 2.6x1 and on RasMol version 2.6.4. Please read the file NOTICE for important notices which apply to this package. If you are not going to make changes to RasMol, you are not only permitted to freely make copies and distribute them, you are encouraged to do so, provided you do the following:

• 1. Either include the complete documentation, especially the file NOTICE, with what you distribute or provide a clear indication where people can get a copy of the documentation; and
• 2. Please give credit where credit is due citing the version and original authors properly; and
• 3. Please do not give anyone the impression that the original authors are providing a warranty of any kind.

If you would like to use major pieces of RasMol in some other program, make modifications to RasMol, or in some other way make what a lawyer would call a "derived work", you are not only permitted to do so, you are encouraged to do so. In addition to the things we discussed above, please do the following:

• 4. Please explain in your documentation how what you did differs from this version of RasMol; and
• 5. Please make your modified source code available.

This version of RasMol is not in the public domain, but it is given freely to the community in the hopes of advancing science. If you make changes, please make them in a responsible manner, and please offer us the opportunity to include those changes in future versions of RasMol.

Table of Contents

1. Notices
2. Introduction
3. General Operation
   • Running RasMol Under UNIX or VMS
   • Running RasMol Under Microsoft Windows
   • Running RasMol on the Apple Macintosh/PPC
   • RasMol's Window
   • Mouse Controls
   • Scroll Bars
   • Picking
   • Dials Box
   • Command Line Interface
   • Dimensions within RasMol
   • Start-up Initialisation Files
   • Inter-Process Communication (IPC)
4. Command Reference

   Backbone	Background	Cartoon	Centre	Clipboard	Colour	Connect	CPK
   Define	Dots	Echo	Exit	HBonds	Help	Label	Load
   Monitor	Pause	Print	Quit	Refresh	Renumber	Reset	Restrict
   Ribbons	Rotate	Save	Script	Select	Set	Show	Slab
   Source	Spacefill	SSBonds	Star	Stereo	Strands	Structure	Trace
   Translate	Wireframe	Write	Zap	Zoom

5. Internal Parameters

   Ambient	Axes	Background	BackFade	BondMode	Bonds	BoundBox	Cartoon
   CisAngle	Display	FontSize	FontStroke	HBonds	Hetero	HourGlass	Hydrogen
   Kinemage	Menus	Monitor	Mouse	Picking	Radius	Shadow	SlabMode
   Solvent	Specular	SpecPower	Stereo	SSBonds	Strands	Transparent	UnitCell
   VectPS	Write

6. Atom Expressions
7. Predefined Sets
8. Colour Schemes
9. File Formats
10. File Machine-Specific Support
11. Bibliography

RasMol Copyright © Roger Sayle 1992-1999
Version 2.6x1 Mods Copyright © Arne Mueller 1998
Version 2.7.0, 2.7.1 Mods Copyright © Herbert J. Bernstein 1998-1999

All rights reserved. Use of copyright notice does not imply publication or disclosure. The information supplied in this document is believed to be true but no liability is assumed for its use or for the infringements of the rights of the others resulting from its use. Information in this document is subject to change without notice and does not represent a commitment on the part of the supplier.

This software has been created from several sources. Much of the code is from RasMol 2.6, as created by Roger Sayle.

See: ftp://ftp.dcs.ed.ac.uk/pub/rasmol

The torsion angle code, new POVRAY3 code and other features are derived from the RasMol2.6x1 revisions by Arne Mueller.

See: ftp://nexus.roko.goe.net/pub/rasmol

The Ramachandran printer plot code was derived from fisipl created by Frances C. Bernstein. See the Protein Data Bank program tape.

The CIF modifications make use of a library based in part on CBFlib by Paul J. Ellis and Herbert J. Bernstein.

See: http://www.bernstein-plus-sons.com/software/CBF

Parts of CBFlib is loosely based on the CIFPARSE software package from the NDB at Rutgers university.

See http://ndbserver.rutgers.edu/NDB/mmcif/software

Please type the RasMol commands 'help copying', 'help general', 'help IUCR', 'help CBFlib', and 'help CIFPARSE' for applicable notices. Please type 'help copyright' for copyright notices. If you use RasMol V2.6 or an earlier version, type the RasMol command 'help oldnotice'.

This version is based on RasMol version 2.6_CIF.2, RasMol 2.6x1 and RasMol_2.6.4. If you are not going to make changes to RasMol, you are not only permitted to freely make copies and distribute them, you are encouraged to do so, provided you do the following:

1. Either include the complete documentation, especially the file NOTICE, with what you distribute or provide a clear indication where people can get a copy of the documentation; and

2. Please give credit where credit is due citing the version and original authors properly; and

3. Please do not give anyone the impression that the original authors are providing a warranty of any kind.

If you would like to use major pieces of RasMol in some other program, make modifications to RasMol, or in some other way make what a lawyer would call a "derived work", you are not only permitted to do so, you are encouraged to do so. In addition to the things we discussed above, please do the following:

4. Please explain in your documentation how what you did differs from this version of RasMol; and

5. Please make your modified source code available.

This version of RasMol is _not_ in the public domain, but it is given freely to the community in the hopes of advancing science. If you make changes, please make them in a responsible manner, and please offer us the opportunity to include those changes in future versions of RasMol.

The following notice applies to this work as a whole and to the works included within it:

* Creative endeavors depend on the lively exchange of ideas. There are laws and customs which establish rights and responsibilities for authors and the users of what authors create. This notice is not intended to prevent you from using the software and documents in this package, but to ensure that there are no misunderstandings about terms and conditions of such use.

* Please read the following notice carefully. If you do not understand any portion of this notice, please seek appropriate professional legal advice before making use of the software and documents included in this software package. In addition to whatever other steps you may be obliged to take to respect the intellectual property rights of the various parties involved, if you do make use of the software and documents in this package, please give credit where credit is due by citing this package, its authors and the URL or other source from which you obtained it, or equivalent primary references in the literature with the same authors.

* Some of the software and documents included within this software package are the intellectual property of various parties, and placement in this package does not in any way imply that any such rights have in any way been waived or diminished.

* With respect to any software or documents for which a copyright exists, ALL RIGHTS ARE RESERVED TO THE OWNERS OF SUCH COPYRIGHT.

* Even though the authors of the various documents and software found here have made a good faith effort to ensure that the documents are correct and that the software performs according to its documentation, and we would greatly appreciate hearing of any problems you may encounter, the programs and documents and any files created by the programs are provided **AS IS** without any warranty as to correctness, merchantability or fitness for any particular or general use.

* THE RESPONSIBILITY FOR ANY ADVERSE CONSEQUENCES FROM THE USE OF PROGRAMS OR DOCUMENTS OR ANY FILE OR FILES CREATED BY USE OF THE PROGRAMS OR DOCUMENTS LIES SOLELY WITH THE USERS OF THE PROGRAMS OR DOCUMENTS OR FILE OR FILES AND NOT WITH AUTHORS OF THE PROGRAMS OR DOCUMENTS.

Subject to your acceptance of the conditions stated above, and your respect for the terms and conditions stated in the notices below, if you are not going to make any modifications or create derived works, you are given permission to freely copy and distribute this package, provided you do the following:

1. Either include the complete documentation, especially the file NOTICE, with what you distribute or provide a clear indication where people can get a copy of the documentation; and

2. Give credit where credit is due citing the version and original authors properly; and

3. Do not give anyone the impression that the original authors are providing a warranty of any kind.

In addition, you may also modify this package and create derived works provided you do the following:

4. Explain in your documentation how what you did differs from this version of RasMol; and

5. Make your modified source code available.

The following notice applies to RasMol V 2.6 and older RasMol versions.

Information in this document is subject to change without notice and does not represent a commitment on the part of the supplier. This package is sold/distributed subject to the condition that it shall not, by way of trade or otherwise, be lent, re-sold, hired out or otherwise circulated without the supplier's prior consent, in any form of packaging or cover other than that in which it was produced. No part of this manual or accompanying software may be reproduced, stored in a retrieval system on optical or magnetic disk, tape or any other medium, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise for any purpose other than the purchaser's personal use.

This product is not to be used in the planning, construction, maintenance, operation or use of any nuclear facility nor the flight, navigation or communication of aircraft or ground support equipment. The author shall not be liable, in whole or in part, for any claims or damages arising from such use, including death, bankruptcy or outbreak of war.

The IUCr Policy on the Use of the Crystallographic Information File (CIF)

The Crystallographic Information File (Hall, Allen & Brown, 1991) is, as of January 1992, the recommended method for submitting publications to Acta Crystallographica Section C. The International Union of Crystallography holds the Copyright on the CIF, and has applied for Patents on the STAR File syntax which is the basis for the CIF format.

It is a principal objective of the IUCr to promote the use of CIF for the exchange and storage of scientific data. The IUCr's sponsorship of the CIF development was motivated by its responsibility to its scientific journals, which set the standards in crystallographic publishing. The IUCr intends that CIFs will be used increasingly for electronic submission of manuscripts to these journals in future. The IUCr recognises that, if the CIF and the STAR File are to be adopted as a means for universal data exchange, the syntax of these files must be strictly and uniformly adhered to. Even small deviations from the syntax would ultimately cause the demise of the universal file concept. Through its Copyrights and Patents the IUCr has taken the steps needed to ensure strict conformance with this syntax.

The IUCr policy on the use of the CIF and STAR File processes is as follows:

1. CIFs and STAR Files may be generated, stored or transmitted, without permission or charge, provided their purpose is not specifically for profit or commercial gain, and provided that the published syntax is strictly adhered to.

2. Computer software may be developed for use with CIFs or STAR files, without permission or charge, provided it is distributed in the public domain. This condition also applies to software for which a charge is made, provided that its primary function is for use with files that satisfy condition 1 and that it is distributed as a minor component of a larger package of software.

3. Permission will be granted for the use of CIFs and STAR Files for specific commercial purposes (such as databases or network exchange processes), and for the distribution of commercial CIF/STAR software, on written application to the IUCr Executive Secretary, 2 Abbey Square, Chester CH1 2HU, England. The nature, terms and duration of the licenses granted will be determined by the IUCr Executive and Finance Committees.

In summary, the IUCr wishes to promote the use of the STAR File concepts as a standard universal data file. It will insist on strict compliance with the published syntax for all applications. To assist with this compliance, the IUCr provides public domain software for checking the logical integrity of a CIF, and for validating the data name definitions contained within a CIF. Detailed information on this software, and the associated dictionaries, may be obtained from the IUCr Office at 5 Abbey Square, Chester CH1 2HU, England.

The following Disclaimer Notice applies to CBFlib V0.1, from which this code in part is derived.

* The items furnished herewith were developed under the sponsorship of the U.S. Government. Neither the U.S., nor the U.S. D.O.E., nor the Leland Stanford Junior University, nor their employees, makes any warranty, express or implied, or assumes any liability or responsibility for accuracy, completeness or usefulness of any information, apparatus, product or process disclosed, or represents that its use will not infringe privately-owned rights. Mention of any product, its manufacturer, or suppliers shall not, nor is it intended to, imply approval, disapproval, or fitness for any particular use. The U.S. and the University at all times retain the right to use and disseminate the furnished items for any purpose whatsoever.

Notice 91 02 01

Portions of this software are loosely based on the CIFPARSE software package from the NDB at Rutgers University. See

http://ndbserver.rutgers.edu/NDB/mmcif/software

CIFPARSE is part of the NDBQUERY application, a program component of the Nucleic Acid Database Project [ H. M. Berman, W. K. Olson, D. L. Beveridge, J. K. Westbrook, A. Gelbin, T. Demeny, S. H. Shieh, A. R. Srinivasan, and B. Schneider. (1992). The Nucleic Acid Database: A Comprehensive Relational Database of Three-Dimensional Structures of Nucleic Acids. Biophys J., 63, 751-759.], whose cooperation is gratefully acknowledged, especially in the form of design concepts created by J. Westbrook.

Please be aware of the following notice in the CIFPARSE API:

This software is provided WITHOUT WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE OR ANY OTHER WARRANTY, EXPRESS OR IMPLIED. RUTGERS MAKE NO REPRESENTATION OR WARRANTY THAT THE SOFTWARE WILL NOT INFRINGE ANY PATENT, COPYRIGHT OR OTHER PROPRIETARY RIGHT.

The program reads in a molecule coordinate file and interactively displays the molecule on the screen in a variety of colour schemes and molecule representations. Currently available representations include depth-cued wireframes, 'Dreiding' sticks, spacefilling (CPK) spheres, ball and stick, solid and strand biomolecular ribbons, atom labels and dot surfaces.

The X Windows version of RasMol provides optional support for a hardware dials box and accelerated shared memory communication (via the XInput and MIT-SHM extensions) if available on the current X Server.

The program reads in molecular coordinate files and interactively displays the molecule on the screen in a variety of representations and colour schemes. Supported input file formats include Protein Data Bank (PDB), Tripos Associates' Alchemy and Sybyl Mol2 formats, Molecular Design Limited's (MDL) Mol file format, Minnesota Supercomputer Center's (MSC) XYZ (XMol) format, CHARMm format, CIF format and mmCIF format files. If connectivity information is not contained in the file this is calculated automatically. The loaded molecule can be shown as wireframe bonds, cylinder 'Dreiding' stick bonds, alpha-carbon trace, space-filling (CPK) spheres, macromolecular ribbons (either smooth shaded solid ribbons or parallel strands), hydrogen bonding and dot surface representations. Atoms may also be labelled with arbitrary text strings. Alternate conformers and multiple NMR models may be specially coloured and identified in atom labels. Different parts of the molecule may be represented and coloured independently of the rest of the molecule or displayed in several representations simultaneously. The displayed molecule may be rotated, translated, zoomed and z-clipped (slabbed) interactively using either the mouse, the scroll bars, the command line or an attached dial box. RasMol can read a prepared list of commands from a 'script' file (or via inter-process communication) to allow a given image or viewpoint to be restored quickly. RasMol can also create a script file containing the commands required to regenerate the current image. Finally, the rendered image may be written out in a variety of formats including either raster or vector PostScript, GIF, PPM, BMP, PICT, Sun rasterfile or as a MolScript input script or Kinemage.

The RasMol help facility can be accessed by typing "help <topic>" or "help <topic> <subtopic>" from the command line. A complete list of RasMol commands may be displayed by typing "help commands". A single question mark may also be used to abbreviate the keyword "help". Please type "help notices" for important notices.

• Running RasMol Under UNIX or VMS
• Running RasMol Under Microsoft Windows
• Running RasMol on the Apple Macintosh/PPC
• RasMol's Window
• Mouse Controls
• Scroll Bars
• Picking
• Dials Box
• Command Line Interface
• Dimensions within RasMol
• Start-up Initialisation Files
• Inter-Process Communication (IPC)

Running RasMol Under UNIX or VMS

     RasMol Molecular Renderer
     Roger Sayle, August 1995
     Copyright (C) Roger Sayle 1992-1999
     Version 2.7.1 June 1999
     Copyright (C) Herbert J. Bernstein 1998-1999
     *** See "help notice" for further notices ***
     [32-bit version]

If the program is run under the X Window System environment with a suitable colour screen, RasMol creates an additional window to display the rendered molecule interactively, as it is manipulated. If RasMol is not run under the X Window System, the program displays the message 'No suitable display detected!'. RasMol may be instructed not to display a graphics window by using the command line option '-nodisplay'. This is particularly useful for running RasMol as a background or batch process.

It is possible to specify either a coordinate filename or a script filename or both on the UNIX/VMS command line. A script file may be specified by adding the option '-script <filename>' to the command line. A molecule coordinate file may be specified by placing its name on the command line, optionally preceded by a file format option. If no format option is given, the specified coordinate file is assumed to be in PDB, CIF or mmCIF format. Valid format options include '-pdb', '-mdl', '-mol2', '-xyz', '- alchemy', '-charmm', '-mopac' and '-cif' which correspond to Protein Data Bank format, Molecular Design Limited's Mol file format, Tripos's Sybyl Mol2 file format, MSC's XMOL XYZ file format, Tripos's Alchemy file format, CHARMm file format, J. P. Stewart's MOPAC file format and IUCr CIF or mmCIF file format, respectively. If both a coordinate file and a script file are specified on the command line, the molecule is loaded first, then the script commands are applied to it. If either file is not found, the program displays the error message 'Error: File not found!' and the user is presented the RasMol prompt.

In order to leave RasMol, the user can type the command quit or exit at the RasMol prompt, and the program will return the user to the familiar unix prompt. Alternatively, if a prompt other than the main RasMol prompt is being displayed, the user may hit control-C (^C) to leave the program. The message '***Quit***' will be output to the terminal, before the usual unix prompt is redisplayed. The program may also be terminated by selecting the Quit menu option, on the bottom of the main menu.

Running RasMol Under Microsoft Windows

It is possible to specify either a coordinate filename or a script filename or both on the windows command line. A script file may be specified by adding the option '-script <filename>' to the command line. A molecule coordinate file may be specified by placing its name on the command line, optionally preceded by a file format option. If no format option is given, the specified coordinate file is assumed to be in PDB, CIF or mmCIF format. Valid format options include '-pdb', '-mdl', '-mol2', '-xyz', '- alchemy', '-charmm', '-mopac' and '-cif' which correspond to Protein Data Bank format, Molecular Design Limited's Mol file format, Tripos's Sybyl Mol2 file format, MSC's XMOL XYZ file format, Tripos's Alchemy file format, CHARMm file format, J. P. Stewart's MOPAC file format and IUCr CIF or mmCIF file format, respectively. If both a coordinate file and a script file are specified on the command line, the molecule is loaded first, then the script commands are applied to it. If either file is not found, the program displays the error message 'Error: File not found!' and the user is presented the RasMol prompt.

Running RasMol on the Apple Macintosh/PPC

Dragging and dropping multi-file 'movie' scripts onto aliases or copies of the RasMol application file may fail due to confusion about which is the correct script folder. Double-clicking on a script may lead to similar problems if copies are present.

Note that because on a Macintosh only one 'instance' of an application may be running at any one time, if you were double click on another file owned by 'RSML', the running copy of RasMol would zap its molecule and load the newly specified file.

RasMol's Window

While the mouse pointer is located within the graphics area of the main display window, the mouse pointer is drawn as a cross-hair cursor, to enable the 'picking' of objects being displayed; otherwise the mouse pointer is drawn as an arrowhead. Any characters that are typed at the keyboard while the display window is in 'focus' (meaning active or foreground) are redirected to the command line in the terminal window. Hence you do not need continually to switch focus between the command line and graphics windows.

The display window may be resized at any point during the session. This has the effect of simply rescaling the image displayed on the canvas. RasMol imposes limits on the size of the display window such that the window must be large enough to display the menu and scroll bars and yet small enough to fit on a single screen. Attempts to enlarge the screen may fail owing to insufficient memory on the host machine, in which case RasMol reports the error message 'Renderer Error: Unable to allocate frame buffer!' or some similar error.

On eight bit displays, when the number of colours required by the program exceeds the number of free colours on the screen, the program uses its own colourmap. This has the effect of temporarily displaying all windows other than the display window in false colours while the mouse pointer is within the display windows. If the mouse pointer is moved outside the display windows, the original colours of the other windows return, and the image on the canvas is shown in 'false colour'. Once the number of colours required by the program drops again, the presentation of colours returns to normal.

Mouse Controls

Scroll Bars

Picking

The program will display, in the terminal window, the atom's type, serial number, residue name and residue number. If the atom is a member of a named chain, the chain identifier is also displayed. Two examples of the output generated by selecting an atom are displayed below:

     Atom:  CA 349       Group:  SER 70
     Atom:  O  526       Hetero:  HOH 205    Chain:  P

Clicking the mouse on an atom can be used not only to identify it, but also to find the coordinates, the distances between two atoms (or to display a distance monitor), the bond angle defined by three atoms, the torsion angle defined by four atoms, to toggle labels on or off, or to specify the centre of rotation. See the 'set picking' command for details.

Dials Box

The rotation about the X and Y axes automatically updates the indicators on the appropriate scroll bars. All the rotation dials rotate the molecule 180 degrees for a complete revolution of the dial. All the remaining dials clamp their values to permissible ranges; turning these dials past their limits has no effect. The centre of rotation of the molecule may be changed using the 'centre' command on the command line, or the command 'set picking centre' followed by a mouse click.

The 'ZOOM' dial allows the interactive zooming of the molecule between 10% and 200% of the original default magnification. Rotating the dial clockwise magnifies the molecule and anticlockwise shrinks it. A complete revolution of the dial corresponds to a 100% change in scale.

The 'SLAB' dial, which is only effective when slabbing is enabled, allows the user to move the front z-clipping plane from the nearest point on the molecule to the furthest. A complete rotation of the SLAB dial corresponds to moving the clipping plane half the distance between the front and back of the molecule. Turning the SLAB knob clockwise moves the clipping plane closer to the viewer (increasing the number of objects displayed), and turning it anticlockwise moves it further away (preventing more objects from being displayed). Slabbing mode is enabled by typing the command 'slab on' on the command line or toggling the slab option on the options menu.

Translation along the X and Y axis allows the centre of the molecule to be moved within the canvas area of the screen. Rotation and zooming are still performed relative to the centre of rotation and the molecule, respectively, which may often not be at the centre of the canvas. The TRANS Z dial currently has no effect.

Command Line Interface

If a syntax error is detected on entering an interactive command, RasMol indicates the location of the error on the command line by placing the '^' character under the offending word or character, and writing an error message on the following line. If a command is not recognised by RasMol, the program will generate an 'Unrecognised command!' error and redisplay the main prompt. If surplus information is given at the end of a command line, RasMol will execute the recognised command, but issue the warning message 'Warning: Ignoring rest of command!'. Some commands may prompt the user for more information. These commands display a different prompt and are discussed in the command reference.

Whenever RasMol outputs diagnostic or error messages to the screen owing to selecting options from the menu or picking objects on the screen, the current command line is cleared. The prompt is redisplayed after any text has been displayed.

Command Line Editing

RasMol maintains a history of recently used commands, so that the user never needs to type the same commands repeatedly. Typing ^P (Control-P) on the command line will display the previous command in the history and ^N will display the following command. These commands may be edited using the features described below. Moving forward or backward through the command history undoes the modifications made to the current line. The number of commands retained in the history depends upon their length. RasMol can retain more short command lines and fewer long ones.

Users with the Microsoft Windows version or the X windows version and with 'vt100' or compatible terminals (such as an 'xterm') can use the cursor control characters on the keyboard to abbreviate the control keys. The right and left cursor keys have the same affect as ^F and ^B, moving the cursor forward and back a single character, respectively. Similarly, the up and down cursor keys have the same function as ^P and ^N, producing the previous and next entries in the command history, respectively.

Users with the Macintosh version can use the four 'arrow keys' to move up and down through previous command line entries; and back and forth within a single command line statement. Hitting 'return' or 'enter' at any time will result in the execution of the current, e.g. selected or edited, command line contents.

Dimensions within RasMol

Start-up Initialisation Files

RasMol first looks for the initialisation file in the current directory and if it is not found will look for it in the user's home directory. On all systems the environment variable HOME may be used to name the user's home directory. If no personal initialisation file is found the program looks for the file rasmolrc (or RASMOLRC) in the RasMol system directory pointed to by the environment variable RASMOLPATH. This directory should also contain the on-line help file rasmol.hlp. On UNIX systems RASMOLPATH is typically set to be '/usr/local/lib/rasmol'.

Unlike the command 'script ".rasmolrc"', the program will not generate an error message if the file is not found. The system rasmolrc file is commonly used by system managers to display information about the local installation and who to contact for help. Such system rasmolrc files will contain RasMol 'echo' commands detailing a telephone number or e-mail address to be used for contacting somebody for local assistance.

Inter-Process Communication

When RasMol starts up on an X window system it registers itself with the X window Server as a Tcl interpreter. From within a Tcl application such as 'wish', you can use the Tcl command 'winfo interps' to determine the currently register interpreters on that display. The first instance of RasMol registers itself as 'rasmol', the second as 'rasmol #2', the third as 'rasmol #3' and so on. The Tcl interpreter can easily send a command to rasmol using the built-in 'send' command. RasMol interprets the string parameter to the send command not as a Tcl function to execute but as a RasMol command. Hence, typing 'send {rasmol} {background red}' into the wish interpreter will cause RasMol's display window to change colour. Using the same encoding as Microsoft's DDE Execute protocol, multiple commands may be sent in a single 'send' by placing the consecutive commands in square brackets. RasMol will execute all of the commands in a 'send' before refreshing the screen.

Under Microsoft Windows, RasMol supports a complete DDE protocol. The simplest layers of the protocol may be accessed by sending a DDE Execute command to application 'RasWin' and any topic. This will start a DDE conversation with the most recently launched instance of RasMol. Although any topic name can be used, the use of 'System' and/or 'RemoteControl' are recommended. Once again the contents of the execute package consists of a string for RasMol to execute. If the first non-whitespace character is an open bracket, the string is interpreted to be a sequence of consecutive commands enclosed in square brackets; otherwise the string consists of just a single command. Commands in square brackets may optionally be separated by whitespace and/or semi- colons. RasMol can also act as a 'data server' supporting hot, cold and warm links. Currently supported DDE items include 'Name', 'Image', 'Pick', 'Count' which denotes the Molecule name, the currently displayed image (in Microsoft DIB format), the atom expression of the last picked atom (or an empty string) and the number of selected atoms, respectively. Using a hot or warm link on the 'Pick' item, for example, allows an application such as Microsoft Word, Excel or Visual Basic to respond each time the user clicks on an atom in RasMol.

RasMol on the Apple Macintosh supports AppleEvents. Currently the only supported AppleEvents are the four 'core' events, Open Application, Open Document, Print Document and Quit. However, because OpenDocument determines its actions by the file's type signature this can be used to implement generic IPC. Because RasMol for the Macintosh treats all files of type 'RSML' as scripts, the sending application need only place all the commands to be executed in a temporary file, set the type of the file to 'RSML' and then send RasMol an OpenDocument AppleEvent with the file as parameter.

The commands/keywords currently recognised by RasMol are given below.

Syntax:  backbone {<boolean>}
         backbone <value>
         backbone dash

The RasMol 'backbone' command permits the representation of a polypeptide backbone as a series of bonds connecting the adjacent alpha carbons of each amino acid in a chain. The display of these backbone 'bonds' is turned on and off by the command parameter in the same way as with the 'wireframe' command. The command 'backbone off' turns off the selected 'bonds', and 'backbone on' or with a number turns them on. The number can be used to specify the cylinder radius of the representation in either Ångstrom or RasMol units. A parameter value of 500 (2.0 Ångstroms) or above results in a "Parameter value too large" error. Backbone objects may be coloured using the RasMol 'colour backbone' command.

The reserved word backbone is also used as a predefined set ("help sets") and as a parameter to the 'set hbond' and 'set ssbond' commands. The RasMol command 'trace' renders a smoothed backbone, in contrast to 'backbone' which connects alpha carbons with straight lines.

The backbone may be displayed with dashed lines by use of the 'backbone dash' command.

Syntax:  background <colour>

The RasMol 'background' command is used to set the colour of the "canvas" background. The colour may be given as either a colour name or a comma separated triple of Red, Green and Blue (RGB) components enclosed in square brackets. Typing the command 'help colours' will give a list of the predefined colour names recognised by RasMol. When running under X Windows, RasMol also recognises colours in the X server's colour name database.

The 'background' command is synonymous with the RasMol 'set background' command.

Syntax:  cartoon {<number>}

The RasMol 'cartoon' command does a display of a molecule 'ribbons' as Richardson (MolScript) style protein 'cartoons', implemented as thick (deep) ribbons. The easiest way to obtain a cartoon representation of a protein is to use the 'Cartoons' option on the 'Display' menu. The 'cartoon' command represents the currently selected residues as a deep ribbon with width specified by the command's argument. Using the command without a parameter results in the ribbon's width being taken from the protein's secondary structure, as described in the 'ribbons' command. By default, the C-termini of beta-sheets are displayed as arrow heads. This may be enabled and disabled using the 'set cartoons' command. The depth of the cartoon may be adjusted using the 'set cartoons <number>' command. The 'set cartoons' command without any parameters returns these two options to their default values.

Syntax:  centre {<expression>}
         center {<expression>}

The RasMol 'centre' command defines the point about which the 'rotate' command and the scroll bars rotate the current molecule. Without a parameter the centre command resets the centre of rotation to be the centre of gravity of the molecule. If an atom expression is specified, RasMol rotates the molecule about the centre of gravity of the set of atoms specified by the expression. Hence, if a single atom is specified by the expression, that atom will remain 'stationary' during rotations.

Type 'help expression' for more information on RasMol atom expressions.

Alternatively the centring may be given as a comma separated triple of [CenX, CenY, CenZ] offsets in RasMol units (1/250 of an Ångstrom) from the centre of gravity. The triple must be enclosed in square brackets.

Syntax:  clipboard

The RasMol 'clipboard' command places a copy of the currently displayed image on the local graphics 'clipboard'. Note: this command is not yet supported on UNIX or VMS machines. It is intended to make transfering images between applications easier under Microsoft Windows or on an Apple Macintosh.

When using RasMol on a UNIX or VMS system this functionality may be achieved by generating a raster image in a format that can be read by the receiving program using the RasMol 'write' command.

Syntax:  colour {<object>} <colour>
         color {<object>} <colour>

Colour the atoms (or other objects) of the selected region. The colour may be given as either a colour name or a comma separated triple of Red, Green and Blue (RGB) components enclosed in square brackets. Typing the command 'help colours' will give a list of all the predefined colour names recognised by RasMol.

Allowed objects are 'atoms', 'bonds', 'backbone', 'ribbons', 'labels', 'dots', 'hbonds' and 'ssbonds'. If no object is specified, the default keyword 'atom' is assumed. Some colour schemes are defined for certain object types. The colour scheme 'none' can be applied to all objects except atoms and dots, stating that the selected objects have no colour of their own, but use the colour of their associated atoms (i.e. the atoms they connect). 'Atom' objects can also be coloured by 'alt', 'amino', 'chain', 'charge', 'cpk', 'group', 'model', 'shapely', 'structure', 'temperature' or 'user'. Hydrogen bonds can also be coloured by 'type' and dot surfaces can also be coloured by 'electrostatic potential'. For more information type 'help colour <colour>'.

Syntax:  connect {<boolean>}

The RasMol 'connect' command is used to force RasMol to (re)calculate the connectivity of the current molecule. If the original input file contained connectivity information, this is discarded. The command 'connect false' uses a fast heuristic algorithm that is suitable for determining bonding in large bio-molecules such as proteins and nucleic acids. The command "connect true" uses a slower more accurate algorithm based upon covalent radii that is more suitable to small molecules containing inorganic elements or strained rings. If no parameters are given, RasMol determines which algorithm to use based on the number of atoms in the input file. Greater than 255 atoms causes RasMol to use the faster implementation. This is the method used to determine bonding, if necessary, when a molecule is first read in using the 'load' command.

Syntax:  define <identifier> <expression>

The RasMol 'define' command allows the user to associate an arbitrary set of atoms with a unique identifier. This allows the definition of user-defined sets. These sets are declared statically, i.e. once defined the contents of the set do not change, even if the expression defining them depends on the current transformation and representation of the molecule.

Syntax:  dots {<boolean>}
         dots <value>

The RasMol 'dots' command is used to generate a van der Waals' dot surface around the currently selected atoms. Dot surfaces display regularly spaced points on a sphere of van der Waals' radius about each selected atom. Dots that would are 'buried' within the van der Waals' radius of any other atom (selected or not) are not displayed. The command 'dots on' deletes any existing dot surface and generates a dots surface around the currently selected atom set with a default dot density of 100. The command 'dots off' deletes any existing dot surface. The dot density may be specified by providing a numeric parameter between 1 and 1000. This value approximately corresponds to the number of dots on the surface of a medium sized atom.

By default, the colour of each point on a dot surface is the colour of its closest atom at the time the surface is generated. The colour of the whole dot surface may be changed using the 'colour dots' command.

Syntax:  echo {<string>}

The RasMol 'echo' command is used to display a message in the RasMol command/terminal window. The string parameter may optionally be delimited in double quote characters. If no parameter is specified, the 'echo' command displays a blank line. This command is particularly useful for displaying text from within a RasMol 'script' file.

Syntax:  hbonds {<boolean>}
         hbonds <value>

The RasMol 'hbond' command is used to represent the hydrogen bonding of the protein molecule's backbone. This information is useful in assessing the protein's secondary structure. Hydrogen bonds are represented as either dotted lines or cylinders between the donor and acceptor residues. The first time the 'hbond' command is used, the program searches the structure of the molecule to find hydrogen bonded residues and reports the number of bonds to the user. The command 'hbonds on' displays the selected 'bonds' as dotted lines, and the 'hbonds off' turns off their display. The colour of hbond objects may be changed by the 'colour hbond' command. Initially, each hydrogen bond has the colours of its connected atoms.

By default the dotted lines are drawn between the accepting oxygen and the donating nitrogen. By using the 'set hbonds' command the alpha carbon positions of the appropriate residues may be used instead. This is especially useful when examining proteins in backbone representation.

Syntax:  help {<topic> {<subtopic>}}
         ? {<topic> {<subtopic>}}

The RasMol 'help' command provides on-line help on the given topic.

Syntax:  label {<string>}
         label <boolean>

The RasMol 'label' command allows an arbitrary formatted text string to be associated with each currently selected atom. This string may contain embedded 'expansion specifiers' which display properties of the atom being labelled. An expansion specifier consists of a '%' character followed by a single alphabetic character specifying the property to be displayed (similar to C's printf syntax). An actual '%' character may be displayed by using the expansion specifier '%%'.

Atom labelling for the currently selected atoms may be turned off with the command 'label off'. By default, if no string is given as a parameter, RasMol uses labels appropriate for the current molecule. RasMol uses the label '%n%r:%c.%a' if the molecule contains more than one chain, '%e%i' if the molecule has only a single residue (a small molecule) and '%n%r.%a' otherwise.

The colour of each label may be changed using the 'colour label' command. By default, each label is drawn in the same colour as the atom to which it is attached. The size and spacing of the displayed text may be changed using the 'set fontsize' command. The width of the strokes in the displayed text may be changed using the 'set fontstroke' command.

The following table lists the current expansion specifiers:

    %a      Atom Name
    %b %t   B-factor/Temperature
    %c %s   Chain Identifier
    %e      Element Atomic Symbol
    %i      Atom Serial Number
    %n      Residue Name
    %r      Residue Number
    %M      NMR Model Number (with leading "/")
    %A      Alternate Conformation Identifier (with leading ";")

Syntax:  load {<format>} <filename>

Load a molecule coordinate file into RasMol. Valid molecule file formats are 'pdb' (Protein Data Bank format), 'mdl' (Molecular Design Limited's MOL file format), 'alchemy' (Tripos' Alchemy file format), 'mol2' (Tripos' Sybyl Mol2 file format), 'charmm' (CHARMm file format), 'xyz' (MSC's XMol XYZ file format), 'mopac' (J. P. Stewart's MOPAC file format) or 'cif' (IUCr CIF or mmCIF file format). If no file format is specified, 'PDB', 'CIF', or 'mmCIF' is assumed by default. Only a single molecule may be loaded at a time. To delete a molecule prior to loading another use the RasMol 'zap' command.

The 'load' command selects all the atoms in the molecule, centres it on the screen and renders it as a CPK coloured wireframe model. If the molecule contains no bonds (i.e. contains only alpha carbons), it is drawn as an alpha carbon backbone. If the file specifies fewer bonds than atoms, RasMol determines connectivity using the 'connect' command.

The 'load inline' command also allows the storing of atom coordinates in scripts to allow better integration with WWW browsers. A load command executed inside a script file may specify the keyword 'inline' instead of a conventional filename. This option specifies that the coordinates of the molecule to load are stored in the same file as the currently executing commands.

Typically this is used in the command 'load pdb inline', which is followed by a number of RasMol commands terminated by the command 'exit'. The 'exit' command terminates execution of the current script and returns control to the command line (or the calling script). This means any lines following 'exit' are never interpreted by RasMol. These may be used to store atomic coordinates in PDB, CIF or mmCIF file format. One possible use is a standard RasMol script prefix that may be concatenated with an appropriate PDB file on-the-fly.

Syntax:  monitor <number>  <number>
         monitor {<boolean>}

The RasMol 'monitor' command allows the display of distance monitors. A distance monitor is a dashed (dotted) line between an arbitrary pair of atoms, optionally labelled by the distance between them. The RasMol command 'monitor <number> <number>' adds such a distance monitor between the two atoms specified by the atom serial numbers given as parameters

Distance monitors are turned off with the command 'monitors off'. By default, monitors display the distance between its two end points as a label at the centre of the monitor. These distance labels may be turned off with the command 'set monitors off', and re-enabled with the command 'set monitors on'. Like most other representations, the colour of a monitor is taken from the colour of its end points unless specified by the 'colour monitors' command.

Distance monitors may also be added to a molecule interactively with the mouse, using the 'set picking monitor' command. Clicking on an atom results in its being identified on the rasmol command line. In addition every atom picked increments a modulo counter such that, in monitor mode, every second atom displays the distance between this atom and the previous one. The shift key may be used to form distance monitors between a fixed atom and several consecutive positions. A distance monitor may also be removed (toggled) by selecting the appropriate pair of atom end points a second time.

Syntax:  pause
         wait

The RasMol 'pause' command is used in script files to stop the script file for local manipulation by a mouse, until any key is pushed to restart the script file. 'Wait' is synonymous with 'pause'. This command may be executed in RasMol script files to suspend the sequential execution of commands and allow the user to examine the current image. When RasMol executes a 'pause' command in a script file, it suspends execution of the rest of the file, refreshes the image on the screen and allows the manipulation of the image using the mouse and scroll bars, or resizing of the graphics window. Once a key is pressed, control returns to the script file at the line following the 'pause' command. While a script is suspended the molecule may be rotated, translated, scaled, slabbed and picked as usual, but all menu commands are disabled. The 'pause' can probably be used most effectively with 'echo' commands in education pre-scripted demonstrations, where a description of the current image is presented to the user/student. Typically the command before a 'pause' should be 'echo Press any key to continue'.

Execution of a script can be cancelled by pressing Control-D or Control-Z (on VAX/VMS, Control-C) while standing at a pause. The command 'set picking none' disables picking, which avoids the display of spurious messages whilst a script is suspended at a pause.

Syntax:  print

The RasMol 'print' command sends the currently displayed image to the local default printer using the operating system's native printer driver. Note: this command is not yet supported under UNIX or VMS. It is intended to take advantage of Microsoft Windows and Apple Macintosh printer drivers. For example, this allows images to be printed directly on a dot matrix printer.

When using RasMol on a UNIX or VMS system this functionality may be achieved by either generating a PostScript file using the RasMol 'write ps' or 'write vectps' commands and printing that or generating a raster image file and using a utility to dump that to the local printer.

Syntax:  quit
         exit

Exit from the RasMol program. The RasMol commands 'exit' and 'quit' are synonymous, except within nested scripts. In that case, 'exit' terminates only the current level, while 'quit' terminates all nested levels of scripts.

Syntax:  refresh

The RasMol 'refresh' command redraws the current image. This is useful in scripts to ensure application of a complex list of parameter changes.

Syntax:  renumber {{-} <value>}

The RasMol 'renumber' command sequentially numbers the residues in a macromolecular chain. The optional parameter specifies the value of the first residue in the sequence. By default, this value is one. For proteins, each amino acid is numbered consecutively from the N terminus to the C terminus. For nucleic acids, each base is numbered from the 5' terminus to the 3' terminus. All chains in the current database are renumbered and gaps in the original sequence are ignored. The starting value for numbering may be negative.

Syntax:  reset

The RasMol 'reset' command restores the original viewing transformation and centre of rotation. The scale is set to its default value, 'zoom 100', the centre of rotation is set to the geometric centre of the currently loaded molecule, 'centre all', this centre is translated to the middle of the screen and the viewpoint set to the default orientation.

This command should not be mistaken for the RasMol 'zap' command which deletes the currently stored molecule, returning the program to its initial state.

Syntax:  restrict {<expression>}

The RasMol 'restrict' command both defines the currently selected region of the molecule and disables the representation of (most of) those parts of the molecule no longer selected. All subsequent RasMol commands that modify a molecule's colour or representation affect only the currently selected region. The parameter of a 'restrict' command is a RasMol atom expression that is evaluated for every atom of the current molecule. This command is very similar to the RasMol 'select' command, except 'restrict' disables the 'wireframe', 'spacefill' and 'backbone' representations in the non-selected region.

Type "help expression" for more information on RasMol atom expressions.

Syntax:  ribbons {<boolean>}
         ribbons <value>

The RasMol 'ribbons' command displays the currently loaded protein or nucleic acid as a smooth solid "ribbon" surface passing along the backbone of the protein. The ribbon is drawn between each amino acid whose alpha carbon is currently selected. The colour of the ribbon is changed by the RasMol 'colour ribbon' command. If the current ribbon colour is 'none' (the default), the colour is taken from the alpha carbon at each position along its length.

The width of the ribbon at each position is determined by the optional parameter in the usual RasMol units. By default the width of the ribbon is taken from the secondary structure of the protein or a constant value of 720 (2.88 Ångstroms) for nucleic acids. The default width of protein alpha helices and beta sheets is 380 (1.52 Ångstroms) and 100 (0.4 Ångstroms) for turns and random coil. The secondary structure assignment is either from the PDB file or calculated using the DSSP algorithm as used by the 'structure' command. This command is similar to the RasMol command 'strands' which renders the biomolecular ribbon as parallel depth-cued curves.

Syntax:  rotate <axis> {-} <value>

Rotate the molecule about the specified axis. Permitted values for the axis parameter are "x", "y" and "z". The integer parameter states the angle in degrees for the structure to be rotated. For the X and Y axes, positive values move the closest point up and right, and negative values move it down and left, respectively. For the Z axis, a positive rotation acts clockwise and a negative angle anti-clockwise.

Syntax:  save {pdb} <filename>
         save mdl <filename>
         save alchemy <filename>
         save xyz <filename>

Save the currently selected set of atoms in a Protein Data Bank (PDB), MDL, Alchemy(tm) or XYZ format file. The distinction between this command and the RasMol 'write' command has been dropped. The only difference is that without a format specifier the 'save' command generates a 'PDB' file and the 'write' command generates a 'GIF' image.

Syntax:  script <filename>

The RasMol 'script' command reads a set of RasMol commands sequentially from a text file and executes them. This allows sequences of commonly used commands to be stored and performed by single command. A RasMol script file may contain a further script command up to a maximum "depth" of 10, allowing complicated sequences of actions to be executed. RasMol ignores all characters after the first '#' character on each line allowing the scripts to be annotated. Script files are often also annotated using the RasMol 'echo' command.

The most common way to generate a RasMol script file is to use the 'write script' or 'write rasmol' commands to output the sequence of commands that are needed to regenerate the current view, representation and colouring of the currently displayed molecule.

The RasMol command 'source' is synonymous with the 'script' command.

Scripts may also be created with a text editor.

Syntax:  select {<expression>}

Define the currently selected region of the molecule. All subsequent RasMol commands that manipulate a molecule or modify its colour or representation only affect the currently selected region. The parameter of a 'select' command is a RasMol expression that is evaluated for every atom of the current molecule. The currently selected (active) region of the molecule are those atoms that cause the expression to evaluate true. To select the whole molecule use the RasMol command 'select all'. The behaviour of the 'select' command without any parameters is determined by the RasMol 'hetero' and 'hydrogen' parameters.

Type "help expression" for more information on RasMol atom expressions.

Syntax:  set <parameter> {<option>}

The RasMol 'set' command allows the user to alter various internal program parameters such as those controlling rendering options. Each parameter has its own set or permissible parameter options. Typically, omitting the paramter option resets that parameter to its default value. A list of valid parameter names is given below.

Syntax:  show information
         show phipsi
         show RamPrint
         show selected { group | chain | atom }
         show sequence
         show symmetry

The RasMol 'show' command display details of the status of the currently loaded molecule. The command 'show information' lists the molecule's name, classification, PDB code and the number of atoms, chains, groups it contains. If hydrogen bonding, disulphide bridges or secondary structure have been determined, the number of hbonds, ssbonds, helices, ladders and turns are also displayed, respectively. The command 'show phipsi' shows the phi and psi angles of the currently selected residues and the omega angles of cis peptide bonds. The command 'show RamPrint' (or 'show RPP' or 'show RamachandranPrinterPlot') shows a simple Ramachandran printer plot in the style of Frances Bernstein's fisipl program. The command 'show selected' (or 'show selected group' or 'show selected chain' or 'show selected atom' ) shows the groups (default), chains or atoms of the current selection. The command 'show sequence' lists the residues that comprise each chain of the molecule. The command 'show symmetry' shows the space group and unit cell of the molecule.

Syntax:  slab {<boolean>}
         slab <value>

The RasMol 'slab' command enables, disables or positions the z-clipping plane of the molecule. The program only draws those portions of the molecule that are further from the viewer than the slabbing plane. Integer values range from zero at the very back of the molecule to 100 which is completely in front of the molecule. Intermediate values determine the percentage of the molecule to be drawn.

Syntax:  spacefill {<boolean>}
         spacefill temperature
         spacefill user
         spacefill <value>

The RasMol 'spacefill' command is used to represent all of the currently selected atoms as solid spheres. This command is used to produce both union-of-spheres and ball-and-stick models of a molecule. The command, 'spacefill true', the default, represents each atom as a sphere of van der Waals radius. The command 'spacefill off' turns off the representation of the selected atom as spheres. A sphere radius may be specified as an integer in RasMol units (1/250th Ångstrom) or a value containing a decimal point. A value of 500 (2.0 Ångstroms) or greater results in a "Parameter value too large" error.

The 'temperature' option sets the radius of each sphere to the value stored in its temperature field. Zero or negative values have no effect and values greater than 2.0 are truncated to 2.0. The 'user' option allows the radius of each sphere to be specified by additional lines in the molecule's PDB file using Raster 3D's COLOUR record extension.

The RasMol command 'cpk' is synonymous with the 'spacefill' command.

Syntax:  ssbonds {<boolean>}
         ssbonds <value>

The RasMol 'ssbonds' command is used to represent the disulphide bridges of the protein molecule as either dotted lines or cylinders between the connected cysteines. The first time that the 'ssbonds' command is used, the program searches the structure of the protein to find half-cysteine pairs (cysteines whose sulphurs are within 3 Ångstroms of each other) and reports the number of bridges to the user. The command 'ssbonds on' displays the selected "bonds" as dotted lines, and the command 'ssbonds off' disables the display of ssbonds in the currently selected area. Selection of disulphide bridges is identical to normal bonds, and may be adjusted using the RasMol 'set bondmode' command. The colour of disulphide bonds may be changed using the 'colour ssbonds' command. By default, each disulphide bond has the colours of its connected atoms.

By default disulphide bonds are drawn between the sulphur atoms within the cysteine groups. By using the 'set ssbonds' command the position of the cysteine's alpha carbons may be used instead.

Syntax:  star {<boolean>}
         star temperature
         star user
         star <value>

The RasMol 'star' command is used to represent all of the currently selected atoms as stars (six strokes, one each in the x, -x, y, -y, z and -z directions). The commands 'select not bonded' followed by 'star 75' are useful to mark unbonded atoms in a 'wireframe' display with less overhead than provided by 'spacefill 75'. This can be done automatically for all subsequent wireframe displays with the command 'set bondmode not bonded'.

The command 'star true', the default, represents each atom as a star with strokes length equal to van der Waals radius. The command 'star off' turns off the representation of the selected atom as stars. A star stroke length may be specified as an integer in RasMol units (1/250th Ångstrom) or a value containing a decimal point. A value of 500 (2.0 Ångstroms) or greater results in a "Parameter value too large" error.

The 'temperature' option sets the stroke length of each star to the value stored in its temperature field. Zero or negative values have no effect and values greater than 2.0 are truncated to 2.0. The 'user' option allows the stroke length of each star to be specified by additional lines in the molecule's PDB file using Raster 3D's COLOUR record extension.

The RasMol 'spacefill' command can be used for more artistic rendering of atoms as spheres.

Syntax:  stereo on
         stereo <number>
         stereo off

The RasMol 'stereo' command provides side-by-side stereo display of images. Stereo viewing of a molecule may be turned on (and off) either by selecting 'Stereo' from the 'Options' menu, or by typing the commands 'stereo on' or 'stereo off'. The separation angle between the two views may be adjusted with the 'set stereo [-] <number>' command, where positive values result in crossed eye viewing and negative values in relaxed (wall-eyed) viewing. The inclusion of '[-] <number>' in the 'stereo' command, as for example in 'stereo 3' or 'stereo -5', also controls angle and direction.

The stereo command is only partially implemented. When stereo is turned on, the image is not properly recentred. (This can be done with a 'translate x -<number>' command.) It is not supported in vector PostScript output files, is not saved by the 'write script' command, and in general is not yet properly interfaced with several other features of the program.

Syntax:  strands {<boolean>}
         strands <value>

The RasMol 'strands' command displays the currently loaded protein or nucleic acid as a smooth "ribbon" of depth-cued curves passing along the backbone of the protein. The ribbon is composed of a number of strands that run parallel to one another along the peptide plane of each residue. The ribbon is drawn between each amino acid whose alpha carbon is currently selected. The colour of the ribbon is changed by the RasMol 'colour ribbon' command. If the current ribbon colour is 'none' (the default), the colour is taken from the alpha carbon at each position along its length. The central and outermost strands may be coloured independently using the 'colour ribbon1' and 'colour ribbon2' commands, respectively. The number of strands in the ribbon may be altered using the RasMol 'set strands' command.

The width of the ribbon at each position is determined by the optional parameter in the usual RasMol units. By default the width of the ribbon is taken from the secondary structure of the protein or a constant value of 720 for nucleic acids (which produces a ribbon 2.88 Ångstroms wide). The default width of protein alpha helices and beta sheets is 380 (1.52 Ångstroms) and 100 (0.4 Ångstroms) for turns and random coil. The secondary structure assignment is either from the PDB file or calculated using the DSSP algorithm as used by the 'structure' command. This command is similar to the RasMol command 'ribbons' which renders the biomolecular ribbon as a smooth shaded surface.

Syntax:  structure

The RasMol 'structure' command calculates secondary structure assignments for the currently loaded protein. If the original PDB file contained structural assignment records (HELIX, SHEET and TURN) these are discarded. Initially, the hydrogen bonds of the current molecule are found, if this hasn't been done already. The secondary structure is then determined using Kabsch and Sander's DSSP algorithm. Once finished the program reports the number of helices, strands and turns found.

Syntax:  trace {<boolean>}
         trace 
         trace temperature

The RasMol 'trace' command displays a smooth spline between consecutive alpha carbon positions. This spline does not pass exactly through the alpha carbon position of each residue, but follows the same path as 'ribbons', 'strands' and 'cartoons'. Note that residues may be displayed as 'ribbons', 'strands', 'cartoons' or as a 'trace'. Enabling one of these representations disables the others. However, a residue may be displayed simultaneously as backbone and as one of the above representations. This may change in future versions of RasMol. Prior to version 2.6, 'trace' was synonymous with 'backbone'.

'Trace temperature' displays the backbone as a wider cylinder at high temperature factors and thinner at lower. This representation is useful to X-ray crystallographers and NMR spectroscopists.

Syntax:  translate <axis> {-} <value>

The RasMol 'translate' command moves the position of the centre of the molecule on the screen. The axis parameter specifies along which axis the molecule is to be moved and the integer parameter specifies the absolute position of the molecule centre from the middle of the screen. Permitted values for the axis parameter are "x", "y" and "z". Displacement values must be between -100 and 100 which correspond to moving the current molecule just off the screen. A positive "x" displacement moves the molecule to the right, and a positive "y" displacement moves the molecule down the screen. The pair of commands 'translate x 0' and 'translate y 0' centres the molecule on the screen.

Syntax:  wireframe {<boolean>}
         wireframe <value>

The RasMol 'wireframe' command represents each bond within the selected region of the molecule as a cylinder, a line or a depth-cued vector. The display of bonds as depth-cued vectors (drawn darker the further away from the viewer) is turned on by the command 'wireframe' or 'wireframe on'. The selected bonds are displayed as cylinders by specifying a radius either as an integer in RasMol units or containing a decimal point as a value in Ångstroms. A parameter value of 500 (2.0 Ångstroms) or above results in an "Parameter value too large" error. Bonds may be coloured using the 'colour bonds' command.

Non-bonded atoms, which could become invisible in an ordinary 'wireframe' display can be marked by a preceding 'set bondmode not bonded' command. If nearly co-linear bonds to atoms cause them to be difficult to see in a wireframe display, the 'set bondmode all' command will add markers for 'all' atoms in subsequent 'wireframe' command executions.

Syntax:  write {<format>} <filename>

Write the current image to a file in a standard format. Currently supported image file formats include 'bmp' (Microsoft bitmap) and 'gif' (Compuserve GIF), 'iris' (IRIS RGB), 'ppm' (Portable Pixmap), 'ras' (Sun rasterfile), 'ps' and 'epsf' (Encapsulated PostScript), 'monops' (Monochrome Encapsulated PostScript), 'pict' (Apple PICT), 'vectps' (Vector Postscript). The 'write' command may also be used to generate command scripts for other graphics programs. The format 'script' writes out a file containing the RasMol 'script' commands to reproduce the current image. The format 'molscript' writes out the commands required to render the current view of the molecule as ribbons in Per Kraulis' Molscript program and the format 'kinemage' the commands for David Richardson's program Mage. The following formats are useful for further processing: 'povray' (POVRay 2), 'povray3' (POVRay 3 -- under development), 'vrml' (VRML file). Finally, several formats are provided to provide phi-psi data for listing or for 'phipsi' (phi-psi data as an annotated list with cis omegas), 'ramachan' and 'RDF' and 'RamachandranDataFile' (phi-psi data as columns of numbers for gnuplot), 'RPP' and 'RamachandranPrinterPlot' (phi-psi data as a printer plot).

The distinction between this command and the RasMol 'save' command has been dropped. The only difference is that without a format specifier the 'save' command generates a 'PDB' file and the 'write' command generates a 'GIF' image.

Syntax:  zap

Deletes the contents of the current database and resets parameter variables to their initial default state.

Syntax:  zoom {<boolean>}
         zoom <value>

Change the magnification of the currently displayed image. Boolean parameters either magnify or reset the scale of current molecule. An integer parameter specifies the desired magnification as a percentage of the default scale. The minimum parameter value is 10; the maximum parameter value is dependent upon the size of the molecule being displayed. For medium sized proteins this is about 500.

A complete list of internal parameter names is given below.

Syntax:  set ambient {<value>}

The RasMol 'ambient' parameter is used to control the amount of ambient (or surrounding) light in the scene. The 'ambient' value must be between 0 and 100. It controls the percentage intensity of the darkest shade of an object. For a solid object, this is the intensity of surfaces facing away from the light source or in shadow. For depth-cued objects this is the intensity of objects furthest from the viewer.

This parameter is commonly used to correct for monitors with different "gamma values" (brightness), to change how light or dark a hardcopy image appears when printed or to alter the feeling of depth for wireframe or ribbon representations.

Syntax:  set axes <boolean>

The RasMol 'axes' parameter controls the display of orthogonal coordinate axes on the current display. The coordinate axes are those used in the molecule data file, and the origin is the centre of the molecule's bounding box. The 'set axes' command is similar to the commands 'set boundbox' and 'set unitcell' that display the bounding box and the crystallographic unit cell, respectively.

Syntax:  set backfade <boolean>

The RasMol 'backfade' parameter is used to control backfade to the specified background colour, rather than black. This is controlled by the commands 'set backfade on' and 'set backfade off'. For example, this may be used to generate depth-cued images that fade to white, rather than black.

Syntax:  set background {<colour>}

The RasMol 'background' parameter is used to set the colour of the "canvas" background. The colour may be given as either a colour name or a comma separated triple of Red, Green, Blue (RGB) components enclosed in square brackets. Typing the command 'help colours' will give a list of the predefined colour names recognised by RasMol. When running under X Windows, RasMol also recognises colours in the X server's colour name database.

The command 'set background' is synonymous with the RasMol command 'background'.

Syntax:  set bondmode and
         set bondmode or
         set bondmode all
         set bondmode none
         set bondmode not bonded

The RasMol 'set bondmode' command controls the mechanism used to select individual bonds and modifies the display of bonded and non-bonded atoms by subsequent 'wireframe' commands.

When using the 'select' and 'restrict' commands, a given bond will be selected if i) the bondmode is 'or' and either of the connected atoms is selected, or ii) the bondmode is 'and' and both atoms connected by the bond are selected. Hence an individual bond may be uniquely identified by using the command 'set bondmode and' and then uniquely selecting the atoms at both ends.

The 'bondmode [all | none | not bonded]' commands add 'star 75' or 'spacefill 75' markers for the designated atoms to 'wireframe' displays. Stars are used when the specified wireframe radius is zero.

Syntax:  set bonds <boolean>

The RasMol 'bonds' parameter is used to control display of double and triple bonds as multiple lines or cylinders. Currently bond orders are only read from MDL Mol files, Sybyl Mol2 format files, Tripos Alchemy format files, CIF and mmCIF, and suitable PDB files. Double (and triple) bonds are specified in some PDB files by specifying a given bond twice (and three times) in CONECT records. The command 'set bonds on' enables the display of bond orders, and the command 'set bonds off' disables them.

Syntax:  set boundbox <boolean>

The RasMol 'boundbox' parameter controls the display of the current molecule's bounding box on the display. The bounding box is orthogonal to the data file's original coordinate axes. The 'set boundbox' command is similar to the commands 'set axes' and 'set unitcell' that display orthogonal coordinate axes and the bounding box, respectively.

Syntax:  set cartoon {<boolean>}
         set cartoon {<number>}

The RasMol 'cartoon' parameter is used to control display of the cartoon version of the 'ribbons' display. By default, the C-termini of beta-sheets are displayed as arrow heads. This may be enabled and disabled using the 'set cartoons <boolean>' command. The depth of the cartoon may be adjusted using the 'cartoons <number>' command. The 'set cartoons' command without any parameters returns these two options to their default values.

Syntax:  set cisangle {<value>}

The RasMol 'cisangle' parameter controls the cutoff angle for identifying cis peptide bonds. If no value is given, the cutoff is set to 90 degrees.

Syntax:  set display selected
         set display normal

This command controls the display mode within RasMol. By default, 'set display normal', RasMol displays the molecule in the representation specified by the user. The command 'set display selected' changes the display mode such that the molecule is temporarily drawn so as to indicate currently selected portion of the molecule. The user specified colour scheme and representation remains unchanged. In this representation all selected atoms are shown in yellow and all non selected atoms are shown in blue. The colour of the background is also changed to a dark grey to indicate the change of display mode. This command is typically only used by external Graphical User Interfaces (GUIs).

Syntax:  set fontsize {<value>} { FS | PS }

The RasMol 'set fontsize' command is used to control the size of the characters that form atom labels. This value corresponds to the height of the displayed character in pixels. The maximum value of 'fontsize' is 48 pixels, and the default value is 8 pixels high. Fixed or proportional spacing may be selected by appending the "FS" or "PS" modifiers, respectively. The default is "FS". To display atom labels on the screen use the RasMol 'label' command and to change the colour of displayed labels, use the 'colour labels' command.

Syntax:  set fontstroke {<value>}

The RasMol 'set fontstroke' command is used to control the size of the stroke width of the characters that form atom labels. This value is the radius in pixels of cylinders used to form the strokes. The special value of "0" is the default used for the normal single pixel stroke width, which allows for rapid drawing and rotation of the image. Non-zero values are provided to allow for more artistic atom labels for publication at the expense of extra time in rendering the image.

When wider strokes are used, a larger font size is recommend, e.g. by using the RasMol 'set fontsize 24 PS' command, followed by 'set fontstroke 2'

The character sets used by RasMol rendered with fixed spacing with single-pixel-width strokes and with proportional spacing with 2-pixel-radius cylinder strokes are shown in the following sample:

To display atom labels on the screen use the RasMol 'label' command, and to change the colour of displayed labels use the 'colour labels' command.

Syntax:  set hbonds backbone
         set hbonds sidechain

The RasMol 'hbonds' parameter determines whether hydrogen bonds are drawn between the donor and acceptor atoms of the hydrogen bond, 'set hbonds sidechain' or between the alpha carbon atoms of the protein backbone and between the phosphorous atoms of the nucleic acid backbone, 'set hbonds backbone'. The actual display of hydrogen bonds is controlled by the 'hbonds' command. Drawing hydrogen bonds between protein alpha carbons or nucleic acid phosphorous atoms is useful when the rest of the molecule is shown in only a schematic representation such as 'backbone', 'ribbons' or 'strands'. This parameter is similar to the RasMol 'ssbonds' parameter.

Syntax:  set hetero <boolean>

The RasMol 'hetero' parameter is used to modify the 'default' behaviour of the RasMol 'select' command, i.e. the behaviour of 'select' without any parameters. When this value is 'false', the default 'select' region does not include any heterogeneous atoms (refer to the predefined set 'hetero' ). When this value is 'true', the default 'select' region may contain hetero atoms. This parameter is similar to the RasMol 'hydrogen' parameter which determines whether hydrogen atoms should be included in the default set. If both 'hetero' and 'hydrogen' are 'true', 'select' without any parameters is equivalent to 'select all'.

Syntax:  set hourglass <boolean>

The RasMol 'hourglass' parameter allows the user to enable and disable the use of the 'hour glass' cursor used by RasMol to indicate that the program is currently busy drawing the next frame. The command 'set hourglass on' enables the indicator, whilst 'set hourglass off' prevents RasMol from changing the cursor. This is useful when spinning the molecule, running a sequence of commands from a script file or using interprocess communication to execute complex sequences of commands. In these cases a 'flashing' cursor may be distracting.

Syntax:  set hydrogen <boolean>

The RasMol 'hydrogen' parameter is used to modify the "default" behaviour of the RasMol 'select' command, i.e. the behaviour of 'select' without any parameters. When this value is 'false', the default 'select' region does not include any hydrogen, deuterium or tritium atoms (refer to the predefined set 'hydrogen' ). When this value is 'true', the default 'select' region may contain hydrogen atoms. This parameter is similar to the RasMol 'hetero' parameter which determines whether heterogeneous atoms should be included in the default set. If both 'hydrogen' and 'hetero' are 'true', 'select' without any parameters is equivalent to 'select all'.

Syntax:  set kinemage <boolean>

The RasMol 'set kinemage' command controls the amount of detail stored in a Kinemage output file generated by the RasMol 'write kinemage' command. The output kinemage files are intended to be displayed by David Richardson's Mage program. 'set kinemage false', the default, only stores the currently displayed representation in the generated output file. The command 'set kinemage true', generates a more complex Kinemage that contains both the wireframe and backbone representations as well as the coordinate axes, bounding box and crystal unit cell.

Syntax:  set menus <boolean>

The RasMol 'set menus' command enables the canvas window's menu buttons or menu bar. This command is typically only used by graphical user interfaces or to create as large an image as possible when using Microsoft Windows.

Syntax:  set monitor <boolean>

The RasMol 'set monitor' command enables 'monitors'. The distance monitor labels may be turned off with the command 'set monitor off', and re-enabled with the command 'set monitor on'.

Syntax:  set mouse rasmol
         set mouse insight
         set mouse quanta

The RasMol 'set mouse' command sets the rotation, translation, scaling and zooming mouse bindings. The default value is 'rasmol' which is suitable for two button mice (for three button mice the second and third buttons are synonymous); X-Y rotation is controlled by the first button, and X-Y translation by the second. Additional functions are controlled by holding a modifier key on the keyboard. [Shift] and the first button performs scaling, [shift] and the second button performs Z-rotation, and [control] and the first mouse button controls the clipping plane. The 'insight' and 'quanta' options provide the same mouse bindings as other packages for experienced users.

Syntax:  set picking <boolean>
         set picking off
         set picking none
         set picking ident
         set picking distance
         set picking monitor
         set picking angle
         set picking torsion
         set picking label
         set picking centre
         set picking center
         set picking coord

The RasMol 'set picking' series of commands affects how a user may interact with a molecule displayed on the screen in RasMol.

Enabling/Disabling Atom Picking: Clicking on an atom with the mouse results in identification and the display of its residue name, residue number, atom name, atom serial number and chain in the command window. This behavior may be disabled with the command 'set picking none' and restored with the command 'set picking ident'. The command 'set picking coord' adds the atomic coordinates of the atom to the display.

Disabling picking, by using 'set picking off' is useful when executing the 'pause' command in RasMol scripts as it prevents the display of spurious message on the command line while the script is suspended.

Measuring Distances, Angles and Torsions: Interactive measurement of distances, angles and torsions is achieved using the commands: 'set picking distance', 'set picking monitor', 'set picking angle' and 'set picking torsion', respectively. In these modes, clicking on an atom results in it being identified on the rasmol command line. In addition every atom picked increments a modulo counter such that in distance mode, every second atom displays the distance (or distance monitor) between this atom and the previous one. In angle mode, every third atom displays the angle between the previous three atoms and in torsion mode every fourth atom displays the torsion between the last four atoms. By holding down the shift key while picking an atom, this modulo counter is not incremented and allows, for example, the distances of consecutive atoms from a fixed atom to be displayed. See the 'monitor' command for how to control the display of distance monitor lines and labels.

Labelling Atoms with the Mouse: The mouse may also be used to toggle the display of an atom label on a given atom. The RasMol command 'set picking label' removes a label from a picked atom if it already has one or displays a concise label at that atom position otherwise.

Centring Rotation with the Mouse: A molecule may be centred on a specified atom position using the RasMol commands 'set picking centre' or 'set picking center'. In this mode, picking an atom causes all futher rotations to be about that point.

Syntax:  set radius {<value>}

The RasMol 'set radius' command is used to alter the behaviour of the RasMol 'dots' command depending upon the value of the 'solvent' parameter. When 'solvent' is 'true', the 'radius' parameter controls whether a true van der Waals' surface is generated by the 'dots' command. If the value of 'radius' is anything other than zero, that value is used as the radius of each atom instead of its true vdW value. When the value of 'solvent' is 'true', this parameter determines the 'probe sphere' (solvent) radius. The parameter may be given as an integer in rasmol units or containing a decimal point in Ångstroms. The default value of this parameter is determined by the value of 'solvent' and changing 'solvent' resets 'radius' to its new default value.

Syntax:  set shadow <boolean>

The RasMol 'set shadow' command enables and disables ray-tracing of the currently rendered image. Currently only the spacefilling representation is shadowed or can cast shadows. Enabling shadowing will automatically disable the Z-clipping (slabbing) plane using the command 'slab off'. Ray-tracing typically takes about several seconds for a moderately sized protein. It is recommended that shadowing be normally disabled whilst the molecule is being transformed or manipulated, and only enabled once an appropiate viewpoint is selected, to provide a greater impression of depth.

Syntax:  set slabmode <slabmode>

The RasMol 'slabmode' parameter controls the rendering method of objects cut by the slabbing (z-clipping) plane. Valid slabmode parameters are "reject", "half", "hollow", "solid" and "section".

Syntax:  set solvent <boolean>

The RasMol 'set solvent' command is used to control the behaviour of the RasMol 'dots' command. Depending upon the value of the 'solvent' parameter, the 'dots' command either generates a van der Waals' or a solvent accessible surface around the currently selected set of atoms. Changing this parameter automatically resets the value of the RasMol 'radius' parameter. The command 'set solvent false', the default value, indicates that a van der Waals' surface should be generated and resets the value of 'radius' to zero. The command 'set solvent true' indicates that a 'Connolly' or 'Richards' solvent accessible surface should be drawn and sets the 'radius' parameter, the solvent radius, to 1.2 Ångstroms (or 300 RasMol units).

Syntax:  set specular <boolean>

The RasMol 'set specular' command enables and disables the display of specular highlights on solid objects drawn by RasMol. Specular highlights appear as white reflections of the light source on the surface of the object. The current RasMol implementation uses an approximation function to generate this highlight.

The specular highlights on the surfaces of solid objects may be altered by using the specular reflection coefficient, which is altered using the RasMol 'set specpower' command.

Syntax:  set specpower {<value>}

The 'specpower' parameter determines the shininess of solid objects rendered by RasMol. This value between 0 and 100 adjusts the reflection coefficient used in specular highlight calculations. The specular highlights are enabled and disabled by the RasMol 'set specular' command. Values around 20 or 30 produce plastic looking surfaces. High values represent more shiny surfaces such as metals, while lower values produce more diffuse/dull surfaces.

Syntax:  set ssbonds backbone
         set ssbonds sidechain

The RasMol 'ssbonds' parameter determines whether disulphide bridges are drawn between the sulphur atoms in the sidechain (the default) or between the alpha carbon atoms in the backbone of the cysteines residues. The actual display of disulphide bridges is controlled by the 'ssbonds' command. Drawing disulphide bridges between alpha carbons is useful when the rest of the protein is shown in only a schematic representation such as 'backbone', 'ribbons' or 'strands'. This parameter is similar to the RasMol 'hbonds' parameter.

Syntax:  set stereo <boolean>
         set stereo [-] <number>

The RasMol 'set stereo' parameter controls the separation between the left and right images. Turning stereo on and off doesn't reposition the centre of the molecule.

Stereo viewing of a molecule may be turned on (and off) either by selecting 'Stereo' from the 'Options' menu, or by typing the commands 'stereo on' or 'stereo off'.

The separation angle between the two views may be adjusted with the 'set stereo [-] <number>' command, where positive values result in crossed eye viewing and negative values in relaxed (wall-eyed) viewing. Currently, stereo viewing is not supported in 'vector PostScript' output files.

Syntax:  set strands {<value>}

The RasMol 'strands' parameter controls the number of parallel strands that are displayed in the ribbon representations of proteins. The permissible values for this parameter are 1, 2, 3, 4, 5 and 9. The default value is 5. The number of strands is constant for all ribbons being displayed. However, the ribbon width (the separation between strands) may be controlled on a residue by residue basis using the RasMol 'ribbons' command.

Syntax:  set transparent <boolean>

The RasMol 'transparent' parameter controls the writing of transparent GIFs by the 'write gif <filename>' command. This may be controlled by the 'set transparent on' and 'set transparent off' commands.

Syntax:  set unitcell <boolean>

The RasMol 'unitcell' parameter controls the display of the crystallographic unit cell on the current display. The crystal cell is only enabled if the appropriate crystal symmetry information is contained in the PDB, CIF or mmCIF data file. The RasMol command 'show symmetry' display details of the crystal's space group and unit cell axes. The 'set unitcell' command is similar to the commands 'set axes' and 'set boundbox' that display orthogonal coordinate axes and the bounding box, respectively.

Syntax:  set vectps <boolean>

The RasMol 'vectps' parameter is use to control the way in which the RasMol 'write' command generates vector PostScript output files. The command 'set vectps on' enables the use of black outlines around spheres and cylinder bonds producing "cartoon-like" high resolution output. However, the current implementation of RasMol incorrectly cartoons spheres that are intersected by more than one other sphere. Hence "ball and stick" models are rendered correctly but not large spacefilling spheres models. Cartoon outlines can be disabled, the default, by the command 'set vectps off'.

Syntax:  set write <boolean>

The RasMol 'write' parameter controls the use of the 'save' and 'write' commands within scripts, but it may only be executed from the command line. By default, this value is 'false', prohibiting the generation of files in any scripts executed at start-up (such as those launched from a WWW browser). However, animators may start up RasMol interactively: type 'set write on' and then execute a script to generate each frame using the source command.

The logical operators allow complex queries to be constructed out of simpler ones using the standard boolean connectives 'and', 'or' and 'not'. These may be abbreviated by the symbols "&", "|" and "!", respectively. Parentheses (brackets) may be used to alter the precedence of the operators. For convenience, a comma may also be used for boolean disjunction.

The atom expression is evaluated for each atom, hence 'protein and backbone' selects protein backbone atoms, not the protein and [nucleic] acid backbone atoms!

Examples:    backbone and not helix
             within( 8.0, ser70 )
             not (hydrogen or hetero)
             not *.FE and hetero
             8, 12, 16, 20-28
             arg, his, lys

• Primitive Expressions
• Predefined Sets
• Comparison Operators
• Within Expressions
• Examples

The following table gives some useful examples of RasMol atom expressions.

    Expression      Interpretation

    *               All atoms
    cys             Atoms in cysteines
    hoh             Atoms in heterogeneous water molecules
    as?             Atoms in either asparagine or aspartic acid
    *120            Atoms at residue 120 of all chains
    *p              Atoms in chain P
    *.n?            Nitrogen atoms
    cys.sg          Sulphur atoms in cysteine residues
    ser70.c?        Carbon atoms in serine-70
    hem*p.fe        Iron atoms in the Heme groups of chain P
    *.*;A           All atoms in alternate conformation A
    */4             All atoms in model 4

RasMol primitive expressions are the fundamental building blocks of atom expressions. There are two types of primitive expression. The first type is used to identify a given residue number or range of residue numbers. A single residue is identified by its number (position in the sequence), and a range is specified by lower and upper bounds separated by a hyphen character. For example 'select 5,6,7,8' is also 'select 5-8'. Note that this selects the given residue numbers in all macromolecule chains.

The second type of primitive expression specifies a sequence of fields that must match for a given atom. The first part specifies a residue (or group of residues) and an optional second part specifies the atoms within those residues. The first part consists of a residue name, optionally followed by a residue number and/or chain identifier.

A residue name typically consists of up to three alphabetic characters, which are case insensitive. Hence the primitive expressions 'SER' and 'ser' are equivalent, identifying all serine residues. Residue names that contain non-alphabetic characters, such as sulphate groups, may be delimited using square brackets, i.e. '[SO4]'.

The residue number is intended to be the residue's position in the macromolecule sequence, but negative sequence numbers, gaps in numbering, or even reverse numbering are permitted in the PDB format. Care must be taken when specifying both residue name and number. If the group at the specified position isn't the specified residue then no atoms are selected.

The chain identifier is typically a single case-insensitive alphabetic or numeric character. Numeric chain identifiers must be distinguished or separated from residue numbers by a colon character. For example, "SER70A" for the alphabetic chain identifier, "A", or "SER70:1" for the numeric chain identifier, "1".

The second part consists of a period character followed by an atom name. An atom name may be up to four alphabetic or numeric characters. An optional semicolon followed by an alternate conformation identifier may be appended. An optional slash followed by a model number may also be appended.

An atom name may be up to four alphabetic or numeric characters.

An asterisk may be used as a wild card for a whole field and a question mark as a single character wildcard.

Parts of a molecule may also be distinguished using equality, inequality and ordering operators on their properties. The format of such comparison expression is a property name, followed by a comparison operator and then an integer value.

The atom properties that may be used in RasMol are 'atomno' for the atom serial number, 'elemno' for the atom's atomic number (element), 'resno' for the residue number, 'radius' for the spacefill radius in RasMol units (or zero if not represented as a sphere) and 'temperature' for the PDB isotropic temperature value.

The equality operator is denoted either "=" or "==". The inequality operator as either "<>", "!=" or "/=". The ordering operators are "<" for less than, "<=" for less than or equal to, ">" for greater than, and ">=" for greater than or equal to.

Examples:    resno < 23
             temperature >= 900
             atomno == 487

A RasMol 'within' expression allows atoms to be selected on their proximity to another set of atoms. A 'within' expression takes two parameters separated by a comma and surrounded by parentheses. The first argument is an integer value called the "cut-off" distance of the within expression and the second argument is any valid atom expression. The cut-off distance is expressed in either integer RasMol units or Ångstroms containing a decimal point. An atom is selected if it is within the cut-off distance of any of the atoms defined by the second argument. This allows complex expressions to be constructed containing nested 'within' expressions.

For example, the command 'select within(3.2,backbone)' selects any atom within a 3.2 Ångstrom radius of any atom in a protein or nucleic acid backbone. 'Within' expressions are particularly useful for selecting the atoms around an active site.

RasMol atom expressions may contain predefined sets. These sets are single keywords that represent portions of a molecule of interest. Predefined sets are often abbreviations of primitive atom expressions. In some cases the use of predefined sets allows selection of areas of a molecule that could not otherwise be distinguished. A list of the currently predefined sets is given below. In addition to the sets listed here, RasMol also treats element names (and their plurals) as predefined sets containing all atoms of that element type, i.e. the command 'select oxygen' is equivalent to the command 'select elemno=8'.

    AT              Acidic          Acyclic
    Aliphatic       Alpha           Amino
    Aromatic        Backbone        Basic
    Bonded          Buried          CG
    Charged         Cyclic          Cystine
    Helix           Hetero          Hydrogen
    Hydrophobic     Ions            Large
    Ligand          Medium          Neutral
    Nucleic         Polar           Protein
    Purine          Pyrimidine      Selected
    Sheet           Sidechain       Small
    Solvent         Surface         Turn
    Water

This set contains the atoms in the complementary nucleotides adenosine and thymidine (A and T, respectively). All nucleotides are classified as either the set 'at' or the set 'cg' This set is equivalent to the RasMol atom expressions "a,t", and "nucleic and not cg".

The set of acidic amino acids. These are the residue types Asp and Glu. All amino acids are classified as either 'acidic', 'basic' 'or' 'neutral'. This set is equivalent to the RasMol atom expressions "asp, glu" and "amino and not (basic or neutral)".

The set of atoms in amino acids not containing a cycle or ring. All amino acids are classified as either 'cyclic' or 'acyclic'. This set is equivalent to the RasMol atom expression "amino and not cyclic".

This set contains the aliphatic amino acids. These are the amino acids Ala, Gly, Ile, Leu and Val. This set is equivalent to the RasMol atom expression "ala, gly, ile, leu, val".

The set of alpha carbons in the protein molecule. This set is approximately equivalent to the RasMol atom expression "*.CA". This command should not be confused with the predefined set 'helix' which contains the atoms in the amino acids of the protein's alpha helices.

This set contains all the atoms contained in amino acid residues. This is useful for distinguishing the protein from the nucleic acid and heterogeneous atoms in the current molecule database.

The set of atoms in amino acids containing aromatic rings. These are the amino acids His, Phe, Trp and Tyr. Because they contain aromatic rings all members of this set are member of the predefined set 'cyclic'. This set is equivalent to the RasMol atom expressions "his, phe, trp, tyr" and "cyclic and not pro".

This set contains the four atoms of each amino acid that form the polypeptide N-C-C-O backbone of proteins, and the atoms of the sugar phosphate backbone of nucleic acids. Use the RasMol predefined sets 'protein' and 'nucleic' to distinguish between the two forms of backbone. Atoms in nucleic acids and proteins are either 'backbone' or 'sidechain'. This set is equivalent to the RasMol expression "(protein or nucleic) and not sidechain".

The predefined set 'mainchain' is synonymous with the set 'backbone'.

The set of basic amino acids. These are the residue types Arg, His and Lys. All amino acids are classified as either 'acidic', 'basic' or 'neutral'. This set is equivalent to the RasMol atom expressions "arg, his, lys" and "amino and not (acidic or neutral)".

This set contain all the atoms in the current molecule database that are bonded to at least one other atom.

This set contains the atoms in those amino acids that tend (prefer) to be buried inside protein, away from contact with solvent molecules. This set refers to the amino acids preference and not the actual solvent accessibility for the current protein. All amino acids are classified as either 'surface' or 'buried'. This set is equivalent to the RasMol atom expression "amino and not surface".

This set contains the atoms in the complementary nucleotides cytidine and guanosine (C and G, respectively). All nucleotides are classified as either the set 'at' or the set 'cg' This set is equivalent to the RasMol atom expressions "c,g" and "nucleic and not at".

This set contains the charged amino acids. These are the amino acids that are either 'acidic' or 'basic'. Amino acids are classified as being either 'charged' or 'neutral'. This set is equivalent to the RasMol atom expressions "acidic or basic" and "amino and not neutral".

The set of atoms in amino acids containing a cycle or rings. All amino acids are classified as either 'cyclic' or 'acyclic'. This set consists of the amino acids His, Phe, Pro, Trp and Tyr. The members of the predefined set 'aromatic' are members of this set. The only cyclic but non-aromatic amino acid is proline. This set is equivalent to the RasMol atom expressions "his, phe, pro, trp, tyr" and "aromatic or pro" and "amino and not acyclic".

This set contains the atoms of cysteine residues that form part of a disulphide bridge, i.e. half cystines. RasMol automatically determines disulphide bridges, if neither the predefined set 'cystine' nor the RasMol 'ssbonds' command have been used since the molecule was loaded. The set of free cysteines may be determined using the RasMol atom expression "cys and not cystine".

This set contains all atoms that form part of a protein alpha helix as determined by either the PDB file author or Kabsch and Sander's DSSP algorithm. By default, RasMol uses the secondary structure determination given in the PDB file if it exists. Otherwise, it uses the DSSP algorithm as used by the RasMol 'structure' command.

This predefined set should not be confused with the predefined set 'alpha' which contains the alpha carbon atoms of a protein.

This set contains all the heterogeneous atoms in the molecule. These are the atoms described by HETATM entries in the PDB file. These typically contain water, cofactors and other solvents and ligands. All 'hetero' atoms are classified as either 'ligand' or 'solvent' atoms. These heterogeneous 'solvent' atoms are further classified as either 'water' or 'ions'.

This predefined set contains all the hydrogen, deuterium and tritium atoms of the current molecule. This predefined set is equivalent to the RasMol atom expression "elemno=1".

This set contains all the hydrophobic amino acids. These are the amino acids Ala, Leu, Val, Ile, Pro, Phe, Met and Trp. All amino acids are classified as either 'hydrophobic' or 'polar'. This set is equivalent to the RasMol atom expressions "ala, leu, val, ile, pro, phe, met, trp" and "amino and not polar".

This set contains all the heterogeneous phosphate and sulphate ions in the current molecule data file. A large number of these ions are sometimes associated with protein and nucleic acid structures determined by X-ray crystallography. These atoms tend to clutter an image. All 'hetero' atoms are classified as either 'ligand' or 'solvent' atoms. All 'solvent' atoms are classified as either 'water' or 'ions'.

All amino acids are classified as either 'small', 'medium' or 'large'. This set is equivalent to the RasMol atom expression "amino and not (small or medium)".

This set contains all the heterogeneous cofactor and ligand moieties that are contained in the current molecule data file. This set is defined to be all 'hetero' atoms that are not 'solvent' atoms. Hence this set is equivalent to the RasMol atom expression "hetero and not solvent".

All amino acids are classified as either 'small', 'medium' or 'large'. This set is equivalent to the RasMol atom expression "amino and not (large or small)".

The set of neutral amino acids. All amino acids are classified as either 'acidic', 'basic' or 'neutral'. This set is equivalent to the RasMol atom expression "amino and not (acidic or basic)".

The set of all atoms in nucleic acids, which consists of the four nucleotide bases adenosine, cytidine, guanosine and thymidine (A, C, G and T, respectively). All neucleotides are classified as either 'purine' or 'pyrimidine'. This set is equivalent to the RasMol atom expressions "a,c,g,t" and "purine or pyrimidine". The symbols for RNA nucleotides (U, +U, I, 1MA, 5MC, OMC, 1MG, 2MG, M2G, 7MG, OMG, YG, H2U, 5MU, and PSU) are also recognized as members of this set.

This set contains the polar amino acids. All amino acids are classified as either 'hydrophobic' or 'polar'. This set is equivalent to the RasMol atom expression "amino and not hydrophobic".

The set of all atoms in proteins. This consists of the RasMol predefined set 'amino' and common post-translation modifications.

The set of purine nucleotides. These are the bases adenosine and guanosine (A and G, respectively). All nucleotides are either 'purines' or 'pyrimidines'. This set is equivalent to the RasMol atom expressions "a,g" and "nucleic and not pyrimidine".

The set of pyrimidine nucleotides. These are the bases cytidine and thymidine (C and T, respectively). All nucleotides are either 'purines' or 'pyrimidines'. This set is equivalent to the RasMol atom expressions "c,t" and "nucleic and not purine".

This set contains the set of atoms in the currently selected region. The currently selected region is defined by the preceding 'select' or 'restrict' command and not the atom expression containing the 'selected' keyword.

This set contains all atoms that form part of a protein beta sheet as determined by either the PDB file author or Kabsch and Sander's DSSP algorithm. By default, RasMol uses the secondary structure determination given in the PDB file if it exists. Otherwise, it uses the DSSP algorithm as used by the RasMol 'structure' command.

This set contains the functional sidechains of any amino acids and the base of each nucleotide. These are the atoms not part of the polypeptide N-C-C-O backbone of proteins or the sugar phosphate backbone of nucleic acids. Use the RasMol predefined sets 'protein' and 'nucleic' to distinguish between the two forms of sidechain. Atoms in nucleic acids and proteins are either 'backbone' or 'sidechain'. This set is equivalent to the RasMol expression "(protein or nucleic) and not backbone".

All amino acids are classified as either 'small', 'medium' or 'large'. This set is equivalent to the RasMol atom expression "amino and not (medium or large)".

This set contains the solvent atoms in the molecule coordinate file. These are the heterogeneous water molecules, phosphate and sulphate ions. All 'hetero' atoms are classified as either 'ligand' or 'solvent' atoms. All 'solvent' atoms are classified as either 'water' or 'ions'. This set is equivalent to the RasMol atom expressions "hetero and not ligand" and "water or ions".

This set contains the atoms in those amino acids that tend (prefer) to be on the surface of proteins, in contact with solvent molecules. This set refers to the amino acids preference and not the actual solvent accessibility for the current protein. All amino acids are classified as either 'surface' or 'buried'. This set is equivalent to the RasMol atom expression "amino and not buried".

This set contains all atoms that form part of a protein turns as determined by either the PDB file author or Kabsch and Sander's DSSP algorithm. By default, RasMol uses the secondary structure determination given in the PDB file if it exists. Otherwise, it uses the DSSP algorithm as used by the RasMol 'structure' command.

This set contains all the heterogeneous water molecules in the current database. A large number of water molecules are sometimes associated with protein and nucleic acid structures determined by X-ray crystallography. These atoms tend to clutter an image. All 'hetero' atoms are classified as either 'ligand' or 'solvent' atoms. The 'solvent' atoms are further classified as either 'water' or 'ions'.

The table below summarises RasMol's classification of the common amino acids.

Note that the rendering of the hexadecimal-equivalent colors shown here will depend on many factors. Thus, they only approximate how RasMol will render the RGB colors on your computer.

If you frequently wish to use a colour not predefined, you can write a one-line script. For example, if you make the file 'grey.col' containing the line, 'colour [180,180,180] #grey', then the command 'script grey.col' colours the currently selected atom set grey.

The RasMol 'alt' (Alternate Conformer) colour scheme codes the base structure with one colour and applies a limited number of colours to each alternate conformer. In a RasMol built for 8-bit color systems, 4 colours are allowed for alternate conformers. Otherwise, 8 colours are available.

The RasMol 'amino' colour scheme colours amino acids according to traditional amino acid properties. The purpose of colouring is to identify amino acids in an unusual or surprising environment. The outer parts of a protein that are polar are visible (bright) colours and non-polar residues darker. Most colours are hallowed by tradition. This colour scheme is similar to the 'shapely' scheme.

     select all
     select oxygen
     color red
     select carbon
     color white
     select nitrogen
     color blue
     select all

      Offset    Colour    Triple
        +2      white     [255,255,255]
        +3      magenta   [255,0,255]
        +4      red       [255,0,0]
        +5      orange    [255,165,0]
        -3      cyan      [0,255,255]
        -4      green     [0,255,0]
      default   yellow    [255,255,0]

     25 < V          red       [255,0,0]
     10 < V <  25    orange    [255,165,0]
      3 < V <  10    yellow    [255,255,0]
      0 < V <   3    green     [0,255,0]
     -3 < V <   0    cyan      [0,255,255]
    -10 < V <   3    blue      [0,0,255]
    -25 < V < -10    purple    [160,32,240]
          V < -25    white     [255,255,255]

FORMAT(6A1,I5,1X,A4,A1,A3,1X,A1,I4,A1,3X,3F8.3,2F6.2,1X,I3,2X,A4,2A2)