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On 21/06/2011 2:10 AM, E. Nihal Korkmaz wrote:
<blockquote
cite="mid:BANLkTi=+3gUx97CKQXX22J1eBdxPntcgBA@mail.gmail.com"
type="cite">What would you suggest as a short time step? I was
using 0.002 ps.</blockquote>
<br>
I'd suggest starting with maybe 100ps of 0.0005 ps time steps, but
that's probably overkill.<br>
<br>
<blockquote
cite="mid:BANLkTi=+3gUx97CKQXX22J1eBdxPntcgBA@mail.gmail.com"
type="cite"> And just to make sure, would 5 ns of equilibration be
enough for a ~110 amino acid long protein?<br>
</blockquote>
<br>
I guess so. It's cheap.<br>
<br>
Mark<br>
<br>
<blockquote
cite="mid:BANLkTi=+3gUx97CKQXX22J1eBdxPntcgBA@mail.gmail.com"
type="cite">Thanks,<br>
Nihal<br>
<br>
<div class="gmail_quote">On Mon, Jun 20, 2011 at 7:41 AM, Mark
Abraham <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:Mark.Abraham@anu.edu.au">Mark.Abraham@anu.edu.au</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt
0.8ex; border-left: 1px solid rgb(204, 204, 204);
padding-left: 1ex;">
<div text="#000000" bgcolor="#ffffff">
<div class="im"> On 20/06/2011 3:29 PM, E. Nihal Korkmaz
wrote:
<blockquote type="cite">I also checked the output of the
minimization:<br>
<br>
Steepest Descents converged to machine precision in 402
steps,<br>
but did not reach the requested Fmax < 10.<br>
Potential Energy = -1.81875038188621e+04<br>
Maximum force = 3.20769543152855e+02 on atom 331<br>
Norm of force = 2.04356801849931e+01<br>
<br>
I assume the structure is not relaxed enough to start a
simulation. How can I get it minimize further? I
increased the step size up to 0.1 ps, i still get the
same result.<br>
</blockquote>
<br>
</div>
The minimization is probably OK, but a period of
equilibration at a short time step will probably help smooth
the process out. Simulations in implicit solvent have few
explicit degrees of freedom compared to explicit solvent,
and might be rather more susceptible to equilibration issues
if the generated velocities are randomly
not-quite-good-enough.<br>
<font color="#888888"> <br>
Mark</font>
<div>
<div class="h5"><br>
<br>
<blockquote type="cite">Thanks,<br>
Nihal<br>
<br>
<div class="gmail_quote">On Sun, Jun 19, 2011 at 11:48
PM, E. Nihal Korkmaz <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:enihalkorkmaz@gmail.com"
target="_blank">enihalkorkmaz@gmail.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin: 0pt
0pt 0pt 0.8ex; border-left: 1px solid rgb(204,
204, 204); padding-left: 1ex;">Dear all,<br>
<br>
I am trying to simulate a GB simulation of a 112
amino acid long protein. I keep getting these
errors,<br>
<br>
Step 27718, time 55.436 (ps) LINCS WARNING<br>
relative constraint deviation after LINCS:<br>
rms 33.319842, max 438.763717 (between atoms 79
and 81)<br>
bonds that rotated more than 30 degrees:<br>
atom 1 atom 2 angle previous, current,
constraint length<br>
<br>
Step 27718, time 55.436 (ps) LINCS WARNING<br>
relative constraint deviation after LINCS:<br>
rms 0.058237, max 1.390675 (between atoms 91 and
93)<br>
bonds that rotated more than 30 degrees:<br>
atom 1 atom 2 angle previous, current,
constraint length<br>
91 92 50.2 0.1016 0.1065
0.1010<br>
91 93 90.0 0.1002 0.2415
0.1010<br>
91 94 70.2 0.1025 0.1066
0.1010<br>
79 80 90.0 0.1057 1.0667
0.1090<br>
79 81 90.0 1.3066 47.9342
0.1090<br>
85 86 90.0 0.1084 0.1758
0.1090<br>
85 87 90.0 1.0654 0.1668
0.1090<br>
88 89 90.0 0.1097 0.6994
0.1090<br>
88 90 90.0 0.1125 0.1097
0.1090<br>
91 92 50.2 0.1016 0.1065
0.1010<br>
91 93 90.0 0.1002 0.2415
0.1010<br>
91 94 70.2 0.1025 0.1066
0.1010<br>
<br clear="all">
<br>
I am copying my mdp parameters below, I'd
appreciate any suggestions to fix that.<br>
<br>
integrator = sd<br>
tinit = 0<br>
dt = 0.002<br>
nsteps = 2500000<br>
simulation_part = 1<br>
init_step = 1<br>
<br>
nstxout = 5000<br>
nstvout = 5000<br>
nstenergy = 500<br>
nstxtcout = 500<br>
nstlog = 500<br>
<br>
xtc_grps = System<br>
energygrps = System<br>
comm_mode = Linear<br>
; neighbor searching and vdw/pme setting up<br>
nstlist = 10<br>
ns_type = grid<br>
pbc = xyz<br>
rlist = 2.0<br>
<br>
implicit_solvent = GBSA<br>
gb_algorithm = OBC<br>
gb_saltconc = 0.15<br>
rgbradii = 2.0<br>
<br>
coulombtype = Cut-off<br>
fourierspacing = 0.1<br>
pme_order = 6<br>
rcoulomb = 2.0<br>
<br>
vdwtype = Cut-off<br>
rvdw_switch = 1.0<br>
rvdw = 2.0<br>
<br>
; cpt control<br>
tcoupl = V-rescale<br>
tc-grps = System<br>
tau_t = 0.1<br>
ref_t = 300.0<br>
<br>
Pcoupl = Berendsen<br>
pcoupltype = isotropic<br>
tau_p = 1.0<br>
compressibility = 4.5e-5<br>
ref_p = 1.0<br>
<br>
; velocity & temperature control<br>
gen_vel = yes<br>
gen_temp = 300.0<br>
annealing = no<br>
constraints = hbonds<br>
constraint_algorithm = lincs<br>
morse = no<br>
<br>
<br>
Thanks,<br>
-- <br>
Elif Nihal Korkmaz<br>
<br>
Research Assistant <br>
University of Wisconsin - Biophysics <br>
Member of Qiang Cui & Thomas Record Labs<br>
1101 University Ave, Rm. 8359<br>
Madison, WI 53706<br>
Phone: <a moz-do-not-send="true"
href="tel:608-265-3644" value="+16082653644"
target="_blank">608-265-3644</a><br>
Email: <a moz-do-not-send="true"
href="mailto:korkmaz@wisc.edu" target="_blank">korkmaz@wisc.edu</a><br>
<br>
<br>
</blockquote>
</div>
<br>
<br clear="all">
<br>
-- <br>
Elif Nihal Korkmaz<br>
<br>
Research Assistant <br>
University of Wisconsin - Biophysics <br>
Member of Qiang Cui & Thomas Record Labs<br>
1101 University Ave, Rm. 8359<br>
Madison, WI 53706<br>
Phone: <a moz-do-not-send="true"
href="tel:608-265-3644" value="+16082653644"
target="_blank">608-265-3644</a><br>
Email: <a moz-do-not-send="true"
href="mailto:korkmaz@wisc.edu" target="_blank">korkmaz@wisc.edu</a><br>
<br>
<br>
</blockquote>
<br>
</div>
</div>
</div>
<br>
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</blockquote>
</div>
<br>
<br clear="all">
<br>
-- <br>
Elif Nihal Korkmaz<br>
<br>
Research Assistant <br>
University of Wisconsin - Biophysics <br>
Member of Qiang Cui & Thomas Record Labs<br>
1101 University Ave, Rm. 8359<br>
Madison, WI 53706<br>
Phone: 608-265-3644<br>
Email: <a moz-do-not-send="true" href="mailto:korkmaz@wisc.edu"
target="_blank">korkmaz@wisc.edu</a><br>
<br>
<br>
</blockquote>
<br>
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