Calculation of Atom-Centered Partial Charges for Heme

摘要

Atom-centered partial charges are calculated for the Fe-heme in cytochrome P450cam for use in molecular dynamics simulations of polar subslnitcs bound in the active Kile of the enzyme. Charges arc fit to the electrostatic potential produced by ah inilio UHF wavefunetions for an Feporphine model. Bnsis set dependence of these charges is observed using the LANUDZ, LANL2DZ and augmented 6-31G levels of theory. Upon geometry optimization of the enzyme, these charge sets cause varying degrees of distortion of the porphyrin from its crystallogrnphiccally observed conformation. Scaling the charges calculated from the augmented 6~31G basis by 75% reduces the he me distortion while preserving reasonable interactions with a polar substrate. A comparison of the calculated charges with other published values is presented.