Molecular vibrations and normal modes in L-prolyl-glycyl-glycine using Wilson GF matrix method.

Collagen is one of the most important proteins containing mostly proline hydroxyproline and glycine. In collagen, approximately 33 percent of the amino acid residues are glycine and they occur at every third position, whereas remaining percentage is constituted by mainly proline or hydroxyproline and some part by alanine etc. having no definite positional placement in the chain. Thus, a study of conformation of proline and glycine containing dipeptides and tripeptides is important for understanding the conformation of collagen as a sequence of its constituent amino acids. In the present communication, we have studied spectral features of L-proline, L-prolyl-glycine (PG), L-prolyl-alanine (PA), L-glycylglycine (GG), Collagen and L-prolyl-glycyl-glycine (PGG). We have carried out detailed normal mode analysis of only PGG, because interpretation of spectra of other proline and glycine containing peptides can be treated as derivatives of this molecule. Urey-Bradley force field, which involves non-bonded interactions in the gem and cis configurations is used for calculation of normal modes. The "best-fit" set of constants are generated for PGG.