PARTIAL CHARGES BY MULTIPOLE CONSTRAINT - APPLICATION TO THE AMINO-ACIDS

Atom‐centered partial charges which exactly reproduce the lowest several multipoles of a molecule's charge distribution can be obtained in a straightforward and convenient manner from the output of existing electronic structure calculations. The multipole constraint method is demonstrated by a computation of partial charges for the twenty common amino acids. The electron density employed here, derived from a semiempirical MNDO calculation, incorporates Slater‐type orbitals which imbue it with the exponential fall‐off vital to electronic tunneling calculations. In addition, a procedure based on these charges is described which divides the original electron density into two components, a large component with a simple electrostatic potential, and a much smaller residual whose several lowest multipoles vanish. Copyright © 1990 John Wiley & Sons, Inc.