Thank you!
I use the correct “O” in Gly according to .rtp and I checked it
with vmd. There is really a new isopeptide bond. When there is no
bond, after minimization and equilibration, Gly and Lys just
close to each other but they are not connected (in vmd). In my
case they are connected (in vmd, pymol).
When I look on step...pdb, one these residues is exploded (it's
atoms are far from each other outside of the water box).
2011/3/13 Mark Abraham <[email protected]
<mailto:[email protected]>>
On 13/03/2011 8:55 PM, Yulian Gavrilov wrote:
Dear gmx users,
I just started with gromacs.
Can you help me to find my mistake? I already asked about
it, but I did not understand what to do exactly in my case.
I try to run to add a new *isopeptide bone* to connect Lys
and Gly (to make a tetramer of *ubiquitin*). I use AMBER99
force field, Gromacs 4.0.5.
What I did:
1.
I changed names of residues according to AMBER rules
(LYS to LYN etc.).
2.
Added new type of residues to ffamber.rtp (LYN -> LYQ
and GLY -> GLQ that are making a new isopeptide bond)
and added a new line to specbond.dat (LYN NZ 1 GLY C 1
0.13 LYQ GLQ) to make such a bond.
IIRC, this creates a bond between the lysine side-chain amine
N and glycine *backbone* carbonyl C. You must use the atom
name for the side-chain carbonyl carbon (see .rtp entry for
GLY). If you've done this wrong, then specbond will probably
not have made a bond, because the backbone carbonyl C was too
far away. You should check your pdb2gmx output carefully.
1.
2.
Added new bond type, angle type and dihedral type to
ffamber99bon.itp
After running of MD (I've got good minimization and
equilibration – nvt and npt) I've got such an error:
starting mdrun 'Protein in water'
600000 steps, 1200.0 ps.
step 94100, will finish Sun Mar 13 08:15:56 2011
Step 94124, time 188.248 (ps) LINCS WARNING
relative constraint deviation after LINCS:
rms 0.000796, max 0.032792 (between atoms 2454 and 2456)
bonds that rotated more than 30 degrees:
atom 1 atom 2 angle previous, current, constraint length
2454 2457 35.6 0.1522 0.1545 0.1522
And after it the same type of errors with another atoms:
2454 2456 36.1 0.1106 0.1113 0.1090 --> *Gly CA and HA1, HA2*
2454 2455 40.5 0.1114 0.1103 0.1090
.....
2454 2456 90.0 0.1078 0.1479 0.1090
771 773 48.5 0.1011 0.1012 0.1010
......
771 773 39.8 0.1012 0.1005 0.1010 --> *Gly NZ and HZ1, HZ2*
771 772 34.9 0.1012 0.1030 0.1010
.......
2454 2457 102.1 0.1490 38312886396780544.0000 0.1522
2454 2456 83.0 5.9313 39290317874135040.0000 0.1090
.......
First errors are with atoms from the residues with *new
isopeptide bond*. I suppose, that this bond is not good.
Seems like a reasonable hypothesis - but do look at 2454 and
2456 as well. You have to get out your trajectory and a
visualization package and see what is actually going wrong.
The warnings can be symptomatic of a problem that started
elsewhere.
You say you've added new interaction types, but I see no
reason why you would need to. It's chemically so similar to a
backbone peptide that you may as well keep things the same
and model it the same way. Regardless, you should probably
check that the specbond.dat mechanism has created
interactions that make sense. Compare with a normal peptide bond.
Mark
Please can you advice me how yo make this isopeptide bond good?
Can I just remove this hydrogens?
--
Sincerely,
Yulian Gavrilov
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--
Sincerely,
Yulian Gavrilov
