Abstract: MATH/CHEM/COMP 2002, Dubrovnik, June 24-29, 2002

Evidence of Covalent H-bond Interaction in Protein H-bonding Networks

Nenad Juranic, Martin Moncrieffe, Franklin Prendergast, and

Slobodan Macura

Mayo Clinic and Foundation, Mayo Graduate School, Rochester, Minnesota, U.S.A.

Protein backbone H-bonding networks were investigated by metrical CO/CN bond changes of peptide group and by nuclear scalar couplings through H-bond (^h3J_NC’) and through peptide bond (¹J_NC’). H-bonding at the oxygen site of peptide group generally elongates CO bond and forms a more polar H-bond networks, in accordance with the classical model of peptide group electronic structure. In the region of a significant interaction of atomic orbitals through H-bond, as detected by ^h3J_NC’ couplings, an altered electronic structure of peptide group which accommodates the covalent H-bond interaction, is indicated. That structure exhibits shortening of CO distance and is consistent with a less polar peptide H-bond networks. H-bond geometry in the anti-parallel β-sheets is most favorable for the least polarizing H-bond and the highest across-H-bond overlap. On the opposite are α-helices and especially β-turns where the most polar H-bond and low overlap is found. These also state that, on average, an H-bond character goes from more polar to less polar in order: β-turns>α-helices>parallel β-sheets>anti-parallel β-sheets.