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<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Hi Gromacs-users</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I'm trying to do a pulling test in a tubulin
protein.</FONT></DIV>
<DIV><FONT face=Arial size=2>I defined pull and reference groups each composed
by more than 15 atoms.</FONT></DIV>
<DIV><FONT face=Arial size=2>The recence group is frozen during all
simulation.</FONT></DIV>
<DIV><FONT face=Arial size=2>My .ppa file is</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT size=2>
<P>verbose = yes</P>
<P>runtype = afm</P>
<P>group_1 = pull</P>
<P>reference_group = reference</P>
<P>reftype = com</P>
<P>pull_dim = Y N N</P>
<P>; rate in nm/ps</P>
<P>afm_rate1 = 0.1 </P>
<P>; Force constants in kJ/(mol*nm^2)</P>
<P>afm_k1 = 3000</P>
<P>; Directions</P>
<P>afm_dir1 = 1.0 0.0 0.0</P>
<P>; COM (= pull group's COM)</P>
<P>afm_init1 = 12.262807 4.368293
4.509590</FONT></P></DIV>
<DIV><FONT face=Arial size=2>During the simulation I have noticed that the
centre of mass of the pull group (pull) can also move in opposite sense respect
to afm_dir1 (user-defined).</FONT></DIV>
<DIV><FONT face=Arial size=2>In the other hand if I have defined
afm_dir1 = 1.0 0.0 0.0 the pull group, during the pulling test, can move in
direction -1.0 0.0 0.0.</FONT></DIV>
<DIV><FONT face=Arial size=2>Can this depend on the value of spring elastic
constant or on the afm_rate value?</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Another question is about the .pdo
file.</FONT></DIV>
<DIV><FONT face=Arial size=2>Why in Gromacs 3.2 the COM value of the
reference group is allways set to 0.0, in pdo file?</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>
Thanks a lot </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial
size=2> Marco
D</FONT><FONT face=Arial size=2></FONT></DIV>
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