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="../gmxfaq.html">GMX FAQ</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 print out information about the version of Gromacs
90 If this, in contrast, returns the phrase
92 mdrun: command not found.
95 then you have to verify where your version of GROMACS is installed.
97 In the default case, the binaries are located in
98 '/usr/local/gromacs/bin', however, you can ask your local system
99 administrator for more information. If we assume that GROMACS is
100 installed in directory <tt>XXX</tt> you would find the executables (programs) in
101 <tt>XXX/bin</tt>. To be able to access the programs without
102 problems, you will have to edit the login file for your shell. If you
103 use the C shell, this file is called <TT>.cshrc</TT> or
104 <TT>.tcshrc</TT>, and it is located in your home directory. Add a line
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120 Issue this command at the prompt too, or log off and on again to
121 automatically get the environment.
122 You should have an environment variable set now that is called
123 GMXDATA that we will use further on. Let us check whether this was
124 successful using:<br><br>
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137 If it prints a directory name you are ready to rock, otherwise go back two steps.
139 <P><H3><A NAME="examples">Examples</A></H3>
140 Before starting the examples, you have to copy all the neccesary
141 files, to your own directory, let us call it work.
142 Mkdir and chdir to the directory you want to put
143 the examples directory. This directory (named <tt>tutor</tt>)
145 about 20 MB of disk space, when it is completely filled.<br><br>
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151 <tt> mkdir work; cd work
157 then copy the examples: <br><br>
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163 <tt> cp -r $GMXDATA/gromacs/tutor .
169 (NOTE: include the "<TT>.</TT>")<br>
170 If that directory doesn't exist you could look for the files
171 in <tt>/usr/local/share/gromacs/tutor</tt>, or ask your local GROMACS expert.
172 <br> You now have a subdirectory
173 <tt>tutor</tt>. Move there<br><br>
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185 and view the contents of this directory
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198 If all is well you will have seven subdirectories with examples
199 with names like <tt>gmxdemo</tt>, <tt>methanol</tt>,
200 <tt>mixed</tt>, <tt>nmr1</tt>, <tt>nmr2</tt>,
201 <tt>speptide</tt> and <tt>water</tt>.
203 You are encouraged to look up the different programs and
204 file formats in <a href="../online.html">
205 the online manual</a> while you are browsing through the examples.</p>
207 <b>While going through the tutorial you will find questions
208 (<font color="red">in a red font</font>). Try to answer them, to increase
209 your understanding of molecular simulation.</b>
213 <a href="gmxdemo.html"><h3>Go to the first step</h3></a>
216 <H2><A NAME="files">GROMACS files</A></h2>
217 Here is an overview of the most important GROMACS file types that you will
218 encounter during the tutorial.
221 <h3><A NAME="top">Molecular Topology file (<TT><a href="top.html">.top</a></TT>)</A></h3>
223 The molecular topology file is generated by the program <TT>
224 <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
226 to a molecular topology file. This topology file contains a complete
227 description of all the interactions in your peptide or protein.
231 <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>
233 When the <a href="pdb2gmx.html">pdb2gmx</a> program is executed to generate a molecular
234 topology, it also translates the structure file (<TT><a href="pdb.html">.pdb</a></TT> file)
236 structure file (<TT><a href="gro.html">.gro</a></TT> file). The main difference between a
237 <a href="pdb.html">pdb</a> file and a gromos file is their format and that
238 a <TT><a href="gro.html">.gro</a></TT> file can also hold velocities. However, if you do not need the
239 velocities, you can also use a <a href="pdb.html">pdb</a> file in all programs.
240 To generate a box of solvent molecules
241 around the peptide, the program
242 <a href="genbox.html">genbox</a> is used. First the program
243 <a href="editconf.html">editconf</a> should be used to
244 define a box of appropriate size around the molecule.
245 <a href="genbox.html">genbox</a>
246 dissolves a solute molecule (the peptide) into any solvent (in this
247 case water). The output of <TT><a href="genbox.html">genbox</a></TT> is a gromos structure file of
248 the peptide dissolved in water. The <a href="genbox.html">genbox</a> program also changes the
249 molecular topology file (generated by <a href="pdb2gmx.html">pdb2gmx</a>) to add solvent
254 <h3><A NAME="mdp">Molecular Dynamics parameter file (<TT><a href="mdp_opt.html">.mdp</a></TT>)</A></h3>
256 The Molecular Dynamics Parameter (<TT><a href="mdp_opt.html">.mdp</a></TT>) file contains all
257 information about the Molecular Dynamics simulation itself
258 e.g. time-step, number of steps, temperature, pressure etc. The
259 easiest way of handling such a file is by adapting a sample <TT><a href="mdp_opt.html">.mdp</a></TT>
260 file. A <TT><a href="mdp.html">sample mdp file</a></TT>
265 <h3><A NAME="ndx">Index file (<TT><a href="ndx.html">.ndx</a></TT>)</A></h3>
267 Sometimes you may need an index file to specify actions on groups of atoms
268 (e.g. Temperature coupling, accelerations, freezing). Usually the default index
269 groups will be sufficient, so for this demo we will
270 not consider the use of index files.
274 <h3><A NAME="tpr">Run input file (<TT><a href="tpr.html">.tpr</a></TT>)</A></h3>
276 The next step is to combine the molecular structure (<TT><a href="gro.html">.gro</a></TT> file),
277 topology (<TT><a href="top.html">.top</a></TT> file) MD-parameters (<TT><a href="mdp_opt.html">.mdp</a></TT> file) and
279 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
280 <TT><a href="tpb.html">.tpb</a></tt> if you don't have XDR).
281 This file contains all information needed to start a simulation with GROMACS.
282 The <a href="grompp.html">
283 grompp</a> program processes all input files and generates the run input
284 <tt><a href="tpr.html">.tpr</a></tt> file.
288 <h3><A NAME="trx">Trajectory file (<TT><a href="trr.html">.trr</a></TT></A>)</h3>
290 Once the run input file is available, we can start the
291 simulation. The program which starts the simulation is called
292 <a href="mdrun.html">mdrun</a>. The only input file
293 of <TT><a href="mdrun.html">mdrun</a></TT> you usually need to start a run
294 is the run input file (<TT><a href="tpr.html">.tpr</a></TT> file).
296 <TT><a href="mdrun.html">mdrun</a></TT> are the
297 trajectory file (<TT><a href="trr.html">.trr</a></TT> file
298 or <TT><a href="trj.html">.trj</a></TT> if you don't have XDR) and a logfile (
299 <TT><a href="log.html">.log</A></TT> file).
306 <P><H2><A NAME="ref">References</A></h2>
311 <dt><A NAME="berendsen81">Berendsen, H.J.C., Postma, J.P.M., van
312 Gunsteren, W.F., Hermans, J. (1981) <dd><it>Intermolecular
313 Forces</it>, chapter Interaction models for water in relation to
314 protein hydration, pp 331-342. Dordrecht: D. Reidel Publishing Company
317 <dt><A NAME="kabsch83">Kabsch, W., Sander, C. (1983). <dd>Dictionary
318 of protein secondary structure: Pattern recognition of hydrogen-bonded
319 and geometrical features. <it>Biopolymers</it> <b>22</b>,
322 <dt><A NAME="mierke91">Mierke, D.F., Kessler, H. (1991). <dd>Molecular
323 dynamics with dimethyl sulfoxide as a solvent. Conformation of a
324 cyclic hexapeptide. <it>J. Am. Chem. Soc.</it> <b>113</b>, 9446.</dd><p>
326 <dt><A NAME="stryer88">Stryer, L. (1988). <dd><it>Biochemistry</it>
327 vol. 1, p. 211. New York: Freeman, 3 edition.</dd><p>
335 <font size="-1"><a href="http://www.gromacs.org">http://www.gromacs.org</a></font><br>