3 <TITLE>Getting started</TITLE>
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11 <td ALIGN=LEFT VALIGN=TOP WIDTH=280><br><h2>Getting started</h2><font size=-1><A HREF="../online.html">Main Table of Contents</A></font><br><br></td>
12 </TABLE></TD><TD WIDTH="*" ALIGN=RIGHT VALIGN=BOTTOM><p><B>VERSION 4.6<br>
13 Sat 19 Jan 2013</B></td></tr></TABLE>
18 <li><a href="#start">Introduction</a>
20 <li><a href="#setup">Setting up your environment</a>
21 <li><a href="#examples">Examples</a>
23 <li><a href="gmxdemo.html">The GROMACS demo</a>
24 <li><a href="water.html">Water</a>
25 <li><a href="methanol.html">Methanol</a>
26 <li><a href="mixed.html">Water/Methanol mixture</a>
27 <li><a href="speptide.html">Ribonuclease S-Peptide</a>
28 <li><a href="protunf.html">Protein unfolding</a>
29 <li><a href="#files">GROMACS files</a>
31 <li><a href="#top">Molecular topology file</a>
32 <li><a href="#gro">Molecular structure file</a>
33 <li><a href="#mdp">Molecular dynamics parameter file</a>
34 <li><a href="#ndx">Index file</a>
35 <li><a href="#tpr">Run input file</a>
36 <li><a href="#trx">Trajectory file</a>
38 <li><a href="#ref">References</a>
42 More info can be found in the
43 <A HREF="flow.html">flowchart</A>
44 (for a quick overview) and the
45 <A HREF="http://www.gromacs.org/Documentation/FAQs">GROMACS FAQs</A>.
50 <a name="start"><H2>Introduction</A></H2>
52 In this chapter we assume the reader is familiar with Molecular
53 Dynamics and familiar with Unix, including the use of a text editor
54 such as <tt>jot</tt>, <tt>emacs</tt> or <tt>vi</tt>. We furthermore assume the
55 GROMACS software is installed properly on your system. When you see a line
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69 you are supposed to type the contents of that line on your computer.
71 <H3><A NAME="setup">Setting up your environment</A></H3>
73 In order to check whether you have access to the GROMACS software, please
74 start by entering the command:
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87 This command should return a cool quote like:
89 "Whatever Happened to Pong ?" (F. Black)
92 If this, in contrast, returns the phrase
94 luck: command not found.
97 then you have to verify where your version of GROMACS is installed.
99 In the default case, the binaries are located in
100 '/usr/local/gromacs/bin', however, you can ask your local system
101 administrator for more information. If we assume that GROMACS is
102 installed in directory <tt>XXX</tt> you would find the executables (programs) in
103 <tt>XXX/bin</tt>. To be able to access the programs without
104 problems, you will have to edit the login file for your shell. If you
105 use the C shell, this file is called <TT>.cshrc</TT> or
106 <TT>.tcshrc</TT>, and it is located in your home directory. Add a line
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122 Issue this command at the prompt too, or log off and on again to
123 automatically get the environment.
124 You should have an environment variable set now that is called
125 GMXDATA that we will use further on. Let us check whether this was
126 successful using:<br><br>
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139 If it prints a directory name you are ready to rock, otherwise go back two steps.
141 <P><H3><A NAME="examples">Examples</A></H3>
142 Before starting the examples, you have to copy all the neccesary
143 files, to your own directory, let us call it work.
144 Mkdir and chdir to the directory you want to put
145 the examples directory. This directory (named <tt>tutor</tt>)
147 about 20 MB of disk space, when it is completely filled.<br><br>
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153 <tt> mkdir work; cd work
159 then copy the examples: <br><br>
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165 <tt> cp -r $GMXDATA/gromacs/tutor .
171 (NOTE: include the "<TT>.</TT>")<br>
172 If that directory doesn't exist you could look for the files
173 in <tt>/usr/local/share/gromacs/tutor</tt>, or ask your local GROMACS expert.
174 <br> You now have a subdirectory
175 <tt>tutor</tt>. Move there<br><br>
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187 and view the contents of this directory
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200 If all is well you will have seven subdirectories with examples
201 with names like <tt>gmxdemo</tt>, <tt>methanol</tt>,
202 <tt>mixed</tt>, <tt>nmr1</tt>, <tt>nmr2</tt>,
203 <tt>speptide</tt> and <tt>water</tt>.
205 You are encouraged to look up the different programs and
206 file formats in <a href="../online.html">
207 the online manual</a> while you are browsing through the examples.</p>
209 <b>While going through the tutorial you will find questions
210 (<font color="red">in a red font</font>). Try to answer them, to increase
211 your understanding of molecular simulation.</b>
215 <a href="gmxdemo.html"><h3>Go to the first step</h3></a>
218 <H2><A NAME="files">GROMACS files</A></h2>
219 Here is an overview of the most important GROMACS file types that you will
220 encounter during the tutorial.
223 <h3><A NAME="top">Molecular Topology file (<TT><a href="top.html">.top</a></TT>)</A></h3>
225 The molecular topology file is generated by the program <TT>
226 <a href="pdb2gmx.html">pdb2gmx</a></TT>. <a href="pdb2gmx.html">pdb2gmx</a> translates a <a href="pdb.html">pdb</a> structure file of any peptide
228 to a molecular topology file. This topology file contains a complete
229 description of all the interactions in your peptide or protein.
233 <h3><A NAME="gro">Molecular Structure file (<TT><a href="gro.html">.gro</a></TT>, <TT><a href="pdb.html">.pdb</a></TT>)</A></h3>
235 When the <a href="pdb2gmx.html">pdb2gmx</a> program is executed to generate a molecular
236 topology, it also translates the structure file (<TT><a href="pdb.html">.pdb</a></TT> file)
238 structure file (<TT><a href="gro.html">.gro</a></TT> file). The main difference between a
239 <a href="pdb.html">pdb</a> file and a gromos file is their format and that
240 a <TT><a href="gro.html">.gro</a></TT> file can also hold velocities. However, if you do not need the
241 velocities, you can also use a <a href="pdb.html">pdb</a> file in all programs.
242 To generate a box of solvent molecules
243 around the peptide, the program
244 <a href="genbox.html">genbox</a> is used. First the program
245 <a href="editconf.html">editconf</a> should be used to
246 define a box of appropriate size around the molecule.
247 <a href="genbox.html">genbox</a>
248 dissolves a solute molecule (the peptide) into any solvent (in this
249 case water). The output of <TT><a href="genbox.html">genbox</a></TT> is a gromos structure file of
250 the peptide dissolved in water. The <a href="genbox.html">genbox</a> program also changes the
251 molecular topology file (generated by <a href="pdb2gmx.html">pdb2gmx</a>) to add solvent
256 <h3><A NAME="mdp">Molecular Dynamics parameter file (<TT><a href="mdp_opt.html">.mdp</a></TT>)</A></h3>
258 The Molecular Dynamics Parameter (<TT><a href="mdp_opt.html">.mdp</a></TT>) file contains all
259 information about the Molecular Dynamics simulation itself
260 e.g. time-step, number of steps, temperature, pressure etc. The
261 easiest way of handling such a file is by adapting a sample <TT><a href="mdp_opt.html">.mdp</a></TT>
262 file. A <TT><a href="mdp.html">sample mdp file</a></TT>
267 <h3><A NAME="ndx">Index file (<TT><a href="ndx.html">.ndx</a></TT>)</A></h3>
269 Sometimes you may need an index file to specify actions on groups of atoms
270 (e.g. Temperature coupling, accelerations, freezing). Usually the default index
271 groups will be sufficient, so for this demo we will
272 not consider the use of index files.
276 <h3><A NAME="tpr">Run input file (<TT><a href="tpr.html">.tpr</a></TT>)</A></h3>
278 The next step is to combine the molecular structure (<TT><a href="gro.html">.gro</a></TT> file),
279 topology (<TT><a href="top.html">.top</a></TT> file) MD-parameters (<TT><a href="mdp_opt.html">.mdp</a></TT> file) and
281 index file (<TT><a href="ndx.html">ndx</a></TT>) to generate a run input file (<TT><a href="tpr.html">.tpr</a></tt> extension or
282 <TT><a href="tpb.html">.tpb</a></tt> if you don't have XDR).
283 This file contains all information needed to start a simulation with GROMACS.
284 The <a href="grompp.html">
285 grompp</a> program processes all input files and generates the run input
286 <tt><a href="tpr.html">.tpr</a></tt> file.
290 <h3><A NAME="trx">Trajectory file (<TT><a href="trr.html">.trr</a></TT></A>)</h3>
292 Once the run input file is available, we can start the
293 simulation. The program which starts the simulation is called
294 <a href="mdrun.html">mdrun</a>. The only input file
295 of <TT><a href="mdrun.html">mdrun</a></TT> you usually need to start a run
296 is the run input file (<TT><a href="tpr.html">.tpr</a></TT> file).
298 <TT><a href="mdrun.html">mdrun</a></TT> are the
299 trajectory file (<TT><a href="trr.html">.trr</a></TT> file
300 or <TT><a href="trj.html">.trj</a></TT> if you don't have XDR) and a logfile (
301 <TT><a href="log.html">.log</A></TT> file).
308 <P><H2><A NAME="ref">References</A></h2>
313 <dt><A NAME="berendsen81">Berendsen, H.J.C., Postma, J.P.M., van
314 Gunsteren, W.F., Hermans, J. (1981) <dd><it>Intermolecular
315 Forces</it>, chapter Interaction models for water in relation to
316 protein hydration, pp 331-342. Dordrecht: D. Reidel Publishing Company
319 <dt><A NAME="kabsch83">Kabsch, W., Sander, C. (1983). <dd>Dictionary
320 of protein secondary structure: Pattern recognition of hydrogen-bonded
321 and geometrical features. <it>Biopolymers</it> <b>22</b>,
324 <dt><A NAME="mierke91">Mierke, D.F., Kessler, H. (1991). <dd>Molecular
325 dynamics with dimethyl sulfoxide as a solvent. Conformation of a
326 cyclic hexapeptide. <it>J. Am. Chem. Soc.</it> <b>113</b>, 9446.</dd><p>
328 <dt><A NAME="stryer88">Stryer, L. (1988). <dd><it>Biochemistry</it>
329 vol. 1, p. 211. New York: Freeman, 3 edition.</dd><p>
337 <font size="-1"><a href="http://www.gromacs.org">http://www.gromacs.org</a></font><br>