EFFECT OF HYDROGEN-BONDING ON MOLECULAR ELECTROSTATIC POTENTIAL

Electrostatic potential difference maps were calculated for 16 hydrogen bonded complexes typical of hydrogen bonds in proteins. The molecular electrostatic potentials of the complexes and the monomers were characterized by fitting atom centered charges to the molecular electrostatic potential. These charge sets were used to generate the difference maps which were then contoured at arbitrary values of potential energy. The difference maps permit the visualization of the perturbation of the electrostatic potential by hydrogen bond formation. N-methyl acetamide (nma) perturbs a complex more as a donor than acceptor; methyl imidazole results in greater perturbative effects and methanol lesser. The energetic effect of complex formation on interaction with a third molecule was investigated. Hydrogen bond formation stabilizes the electrostatic interaction with a third molecule, nma, in the geometries studied, except when the initial complex is an ion pair.