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On 8/02/2011 2:47 AM, abdullah ahmed wrote:
<blockquote cite="mid:SNT140-w1549CA7E8381CE14A41777A3EB0@phx.gbl"
type="cite">
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Hello, <br>
<br>
I have an input structure with poor torsion angles and after
minimization with gromacs (both steepest descent and congugate
gradient) I found that they were not corrected. There is enough
free space for the torsion angles to be corrected. <br>
(I am sure of this because when I run the same structure in
Insight it is able to correct them. Both programs give very
similar structures with the major difference being the torsion
angles.)<br>
<br>
Has this happened because Gromacs potentials do not penalize poor
omega angles?</blockquote>
<br>
Peptide bonds ordinarily have improper dihedrals on them to keep
them close to planar.<br>
<br>
<blockquote cite="mid:SNT140-w1549CA7E8381CE14A41777A3EB0@phx.gbl"
type="cite"> Or have I done something wrong? (I have added by .mdp
file at the end of the mail)<br>
Is there a way besides applying a restraint to every torsion angle
to induce Gromacs to correct them? <br>
</blockquote>
<br>
EM is a local minimization method, and the result depends on the
method and its parameters. Perhaps choosing a larger step size with
steepest-descent algorithm will fix your issues.<br>
<br>
Mark<br>
<br>
<blockquote cite="mid:SNT140-w1549CA7E8381CE14A41777A3EB0@phx.gbl"
type="cite"><br>
Thank you in advance for you help,<br>
Abdullah<br>
<br>
<br>
<br>
; User spoel (236)<br>
; Wed Nov 3 17:12:44 1993<br>
; Input file<br>
;<br>
cpp = /usr/bin/cpp<br>
define = -DPOSRES <br>
constraints = none<br>
integrator = cg<br>
nsteps = 2000<br>
;<br>
; Energy minimizing stuff<br>
;<br>
emtol = 2<br>
emstep = 0.01<br>
<br>
nstcomm = 1<br>
ns_type = grid<br>
rlist = 1<br>
rcoulomb = 1<br>
rvdw = 1<br>
Tcoupl = no<br>
Pcoupl = no<br>
gen_vel = no<br>
<br>
</blockquote>
<br>
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