A Theoretical Study On The Hydrogen Bond Properties In Polyglycine Peptides

A Theoretical Study on the Hydrogen Bond Properties in Polyglycine PeptidesA theoretical study on the hydrogen bond properties in peptides was carried out by using a simple repeating unit method with B3LYP/6-31G* method. The factors influenced the hydrogen bond strength was discussed. The hydrogen bond energy in polypeptides was estimated. The details are:Four conformations have been studied including strand, 27?ribbon, 310?helix and helix up to 26 repeat units for a series of polyglycine model. The charges have been analyzed and the hydrogen bond strengths have been obtained. The hydrogen bond strengths are clearly indicated by the hydrogen bond acidities and the partial charges of the hydrogen atoms, which have been involved in the formation of the hydrogen bond. There does exist the cooperativity among the hydrogen bonds in the 310-helix and helix structures of peptides. The more the numbers of the hydrogen bonds in the helix structure, the stronger each hydrogen bond is.The NH group was replaced by CH2 in glycine di- /tri-peptide and alanine di-/tri-peptide to estimate the hydrogen bond energy. The HB energy was estimated varied from 2.9 to5.0kcal/mol in different systems. This is insistent with the empirical values.