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<DIV><FONT face=Arial size=2>Dear All,</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I am trying to simulate lipid-water system (340
POPE lipids & 6120 TIP4P Waters), during the solvation by
genbox, It also add the the water at the interior of the bilayer. I removed
those water molecules by my perl script. But after removing these
water molecules I have observed a zone between the lipid head group and
water. I tried to do small simulations (50 to250 ps) using different pressure
coupling but still I am not getting the structure which have homogeneous
arrangement of water over lipid head group. There is uneven distribution of
water across the bilayer. During this sort simulations position restrain on
lipid was applied.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I tried Isotropic, semiisotropic,anisotropic
pressure coupling with the following parameter, but no luck </FONT><FONT
face=Arial size=2></FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Isotropic:</FONT></DIV>
<DIV>
<DIV><FONT face=Arial
size=2>Pcoupl =
Berendsen<BR>Pcoupltype =
isotropic<BR>tau_p
=
2.0<BR>compressibility =
4.5e-5<BR>ref_p
= 1</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>semiisotropic: </FONT></DIV></DIV>
<DIV><FONT face=Arial
size=2>Pcoupl
=
Berendsen<BR>Pcoupltype
=
semiisotropic<BR>tau_p
= 2
2<BR>compressibility =
0
4.5e-5<BR>ref_p
= 0 1.0</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial
size=2>anisotropic:<BR>Pcoupl
=
Berendsen<BR>pcoupltype
=
anisotropic<BR>tau_p
= 10.0
10.0
10.0 0
0
0<BR>compressibility =
4.5e-5 4.5e-5 4.5e-5
0 0
0<BR>ref_p
= 1.0
1.0
1.0
0 0
0</FONT></DIV><FONT face=Arial size=2>
<DIV><BR></FONT><FONT face=Arial size=2>I also tried NVT Ensemble but no success
till now. could some one give some idea what parameters I should take to
overcome this problem. I searched the mailing list this problem discussed so
many time suggestion was after sort simulation (10-20 ps) water
will arrange properly,but I am not able to get proper arrangement of water
molecules. please suggest me where I am doing mistake.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Other parameters od the MDP file.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial
size=2>define =
-DPOSRES_LIPID </FONT></DIV>
<DIV><FONT face=Arial
size=2>integrator
=
md<BR>dt
=
0.002<BR>nsteps
=
25000<BR>nstcomm
=
1<BR>nstxout
=
1000<BR>nstvout
=
500<BR>nstlog
=
100<BR>nstenergy
=
100<BR>nstxtcout
= 500<BR>xtc_precision =
1000<BR>xtc_grps =
POPE
SOL<BR>energygrps =
POPE
SOL<BR>nstlist
=
10<BR>ns_type
=
grid<BR>pbc
=
xyz<BR>rlist
=
0.9<BR>coulombtype
=
PME<BR>rcoulomb
=
0.9<BR>rvdw
=
1.2<BR>fourierspacing
=
0.12<BR>pme_order
=
6<BR>ewald_rtol
=
1e-5<BR>optimize_fft
=
yes<BR>vdw-type
=
Cut-off<BR>gen_vel
=
yes<BR>gen_temp
=
300<BR>gen_seed
=
173529<BR>constraints
= all-bonds<BR>constraint_algorithm =
lincs<BR>unconstrained_start =
no<BR>lincs_order
=
4<BR>lincs_iter
=
1<BR>lincs_warnangle
= 30<BR></DIV></FONT>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Thanks in advance,</FONT></DIV>
<DIV><FONT face=Arial size=2>Alok</FONT></DIV></DIV></FONT></DIV></BODY></HTML>