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<p class="MsoNormal"><span style="font-size: 10pt; font-family: Arial;" lang="EN-US">Dear
GROMCS users, </span></p>

<p class="MsoNormal"><span style="font-size: 10pt; font-family: Arial;" lang="EN-US"> </span></p>

<p class="MsoNormal"><span style="font-size: 10pt; font-family: Arial;" lang="EN-US">I
am trying to convert some GLYCAM parameters in GROMACS format. For this
purpose, I am using the latest GLYCAM parameters downloaded from the RJ. Woods’
website and the examples given in the acpype code (here for the dihedral angles) : <br></span></p><p class="MsoNormal"><br></p><p class="MsoNormal"><a href="http://code.google.com/p/acpype/source/browse/trunk/acpypi.py?spec=svn9&amp;r=9&amp;redir=1">http://code.google.com/p/acpype/source/browse/trunk/acpypi.py?spec=svn9&amp;r=9&amp;redir=1</a><br>
</p><p class="MsoNormal"><br><span style="font-size: 10pt; font-family: Arial;" lang="EN-US"></span></p>



<pre><span style="" lang="EN-GB">-------------------<br><span class="str"># dihedral    idivf        barrier hight/2 kcal/mol  phase degrees       periodicity     comments</span></span></pre><pre><span class="str"><span style="" lang="EN-GB"> X -ca-ca-X    4           14.500*                     180.000                2.000             intrpol.bsd.on C6H6</span></span><span style="" lang="EN-GB"><br>
<span class="str">* to convert to gmx: 14.5/4 * 4.184 * 2 (?) (yes in amb2gmx, no in topolbuild, why?) = 30.334 or 15.167 kJ/mol</span><br><span class="str"># X -CA-CA-X    4   14.50        180.0             2.         </span></span><span class="str"><span style="" lang="PT-BR">intrpol.bsd.on C6H6 (from parm99.dat)</span></span><span style="" lang="PT-BR"><br>
<span class="str"># X-CA-CA-X     3    30.33400     0.00000   -30.33400     0.00000     0.00000     0.00000   ; intrpol.bsd.on C6H6</span><br>
-----------</span></pre><pre><span style="" lang="PT-BR"> </span></pre><pre><span style="" lang="EN-GB">I have no problems with the parameters for proteins. But, in case of the GLYCAM parameters, I am a little confused <br>
about the conversion of dihedral force constants (DFC), especially when the DFC and the periodicity values are &lt; 0 for example <br>for this torsion:<br> <br></span></pre>

<p class="MsoNormal" style=""><span style="font-size: 10pt; font-family: &quot;Courier New&quot;;" lang="PT-BR">O2-P -OS-CP<span style="">   </span>1<span style="">    </span>0.10<span style="">          </span>0.0<span style="">            </span>-3.<span style="">         </span>Dimethyl phosphate</span></p>


<p class="MsoNormal" style=""><span style="font-size: 10pt; font-family: &quot;Courier New&quot;;" lang="PT-BR"><span style="">              </span></span><span style="font-size: 10pt; font-family: &quot;Courier New&quot;;">1<span style="">   </span>-0.50<span style="">          </span>0.0<span style="">            </span>-2.</span></p>


<p class="MsoNormal" style=""><span style="font-size: 10pt; font-family: &quot;Courier New&quot;;"><span style="">              </span>1<span style="">    </span>0.10<span style="">          </span>0.0<span style="">             </span>1</span></p>


<pre><span style="" lang="EN-GB"> </span></pre><pre><span style="" lang="EN-GB">Thank you in advance, for your help</span></pre><pre><span style="" lang="EN-GB"> </span></pre><pre><span style="" lang="EN-GB">SA</span></pre>