[AMBER] RESP fitting

From: Mahmood Jasim <ddfd09.gmail.com>
Date: Wed, 19 Aug 2015 13:46:21 +0100


 esp.in
<https://drive.google.com/file/d/0B2P4Qp842kSiY0tHZ2JnQzI0NGM/view?usp=drive_web>
​Hi Amber Users

I have problems with RESP fitting. I am using GAMESS to generate the
electrostatic grid for my ligand and I am using the "Run.resp" script
(attached) to generate the input files for RESP (resp.in and esp.in
attached). I then run RESP using:

resp -i resp.in -o resp.out -e esp.in

I do get the out file (resp.out attached) but the charges are so extreme
ranging from -21 to 21 although the electrostatic grid has been generated
by an optimisation calculation in GAMESS. Also when I use a programme
called Molby to assign the charges, the latter gives mereasonable values
for the charges.

I cannot use Molby because I have a cap attached to my molecule composed of
the final 5 atoms. I modified the resp.in file (resp_cap.in attached) to
fix the charges of the cap according to their values in the Amber
forcefield and created a file for the fixed charges of the cap (SCH3_cap
attached) and ran RESP as:

resp -i resp_cap.in -o resp_cap.out -e esp.in -q SCH3_cap.qin

The file shows this "not enough (possibly none) q0 are given in file
ESP.Q0, so the remaining old ones will be used." and the charges of the cap
atoms are fixed to zero.

Could anyone please help me with this?

Best Regards,
Mahmood Jasim


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Received on Wed Aug 19 2015 - 06:00:06 PDT
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