Peggy Yao wrote:
Dear Gromacs users,
Thanks for earlier help on this problem.
I have tried a number of approaches with varying results (all bad,
unfortunately). I am trying to add two CA2+ ions to my protein (1k9p),
but when I did this genion put the two CA2+ ions very close together and
they flew apart. Then I tried putting only one CA2+, thinking that it
would stay put. After I ran an energy minimization, the CA2+ ended up
outside of the box. Now I am really perplexed. What could be causing
this behavior? One thing I haven't tried yet is adding a few CL- ions
to make the box neutral .. somehow I don't feel this is the problem
though since I've run non-neutral analyses before without such
disastrous consequences.
Could anyone give me some advice? I'm at my wit's end. I am attaching
my script below. Basically fws_ca.pdb is fine, but fws_b4ion.pdb has
CA2+ outside of the water box. The water in the water box looks like
ice cubes in an ice cube tray, segregated into regular little
mini-boxes. I presume the latter is a numerical consequence of the CA2+
flying out of the box.
try with position restraints on protein and Ca2+ and without water first.
Many thanks for any help..
Peggy
pdb2gmx -ignh -ff gmx -f 1K9P.pdb -p fws.top -o fws.pdb
# add water
editconf -bt cubic -f fws.pdb -o fws.pdb -c -d 0.9
genbox -cp fws.pdb -cs spc216.gro -o fws_b4em.pdb -p fws.top
# energy minimization
grompp -f minim.mdp -c fws_b4em.pdb -p fws.top -o fws_em.tpr
echo "check 2"
mdrun -v -s fws_em.tpr -o fws_em.trr -c fws_b4ca.pdb -g em.log -e em.edr
# add calcium
grompp -f minim.mdp -c fws_b4ca.pdb -p fws.top -o fws_ca.tpr
echo "12" | genion -s fws_ca.tpr -o fws_ca.pdb -pname Ca -np 1 -g
fws_ca.log -norandom
awk '{if ($1 == "SOL") {print "Ca 1"; print "SOL 7280"} else {print
$0;}}' fws.top > temp.top
mv temp.top fws.top
# energy minimization
grompp -f minim.mdp -c fws_ca.pdb -p fws.top -o fws_em2.tpr
mdrun -v -s fws_em2.tpr -o fws_em2.trr -c fws_b4ion.pdb -g em.log -e em.edr
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--
David van der Spoel, Ph.D.
Molec. Biophys. group, Dept. of Cell & Molec. Biol., Uppsala University.
Box 596, 75124 Uppsala, Sweden. Phone: +46184714205. Fax: +4618511755.
[EMAIL PROTECTED] [EMAIL PROTECTED] http://folding.bmc.uu.se
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