Hi, I am trying to use MCPB for parameterization of a protein complex with
two zinc ions. I have been following the tutorial included in the MTK++
manual. I am able to run all calculations without any problems. However,
when I try to create the XML libraries containing the RESP charges, I run
into some trouble. the overall charge on the model is 0 (and this is what is
used when doing the Gaussian charge calculations).
problem: When I run "MCPB -i NAME_large_mk1.bcl", the generated .ac file has
a charge of 1.32 and therefore 1 is used for the RESP calculations, and when
I generate the final XML files including the new charges, the overall charge
is -0.1557. I also attempted to manually edit the .ac file to change the
charge to 0, and run the resp calculation again. However, this resulted in
the same overall charge. This is true for all 4 resp methods (0, 1, 2, and
3).
my large model (used for the charge calculations) has the following
sequence, and the sidechain model (used for FC calculations) does not
include the GLU residue that connects the two histidines or the capping
residues (NME and ACE)
ACE HID GLU HID NME ACE ASP NME ACE KCX NME ACE HID NME ACE HIE NME ZN1 ZN2
MOH HOH
I'm assuming that the problem arises from how the charges of the capping
residues (ACE NME) are handled, but I am not sure. any help would be
appreciated.
Note: I also attempted to change the GLU residue charge to an integer -1 and
re-ran RESP, but this also did not help.
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Received on Thu Apr 21 2011 - 16:00:03 PDT
