Hydrogen bonding in protein circular dichroism calculations

We present ab initio electronic structure calculations of N-methylacetamide (NMA) in solution. The solvent is modelled by a combination of explicitly defined water molecules and a continuum dielectric. This should describe both local and bulk solvent effects; in particular the effects of solute-solvent hydrogen bonds will be included. The influence of hydrogen bonding on calculations of the electronic circular dichroism (CD) spectra of proteins is explicitly incorporated through parameters derived from the ab initio calculations. We find no improvement on the accuracy of protein CD calculations compared with results from parameters for NMA in continuum solvent. We conclude that hydrogen bonding is probably adequately described through interamide electrostatic interactions that form the basis of the matrix method. (C) 2000 Elsevier Science B.V. All rights reserved.