Vibrational spectra of N-acetylglycine oligomers Part 2.—Raman scattering study of selectively C-deuteriated oligomers with polyglycine I- and II-type structures

Abstract

Selectively C-deuteriated N-acetylglycine trimer and tetramer acid types have been synthesized, and their two crystalline modifications, solid-A and solid-B [which correspond in structure to polyglycine (PG) II and I, respectively] have been prepared. Raman scattering spectra have been measured for a series of these glycine oligomers, and the CH ₂ - and CD ₂ -characteristic modes have been investigated in detail. Assignment of the CH ₂ -characteristic bands to each CH ₂ group in the oligomers has been carried out successfully. In particular, the results obtained from the CD ₂ stretch region show that N- and C-terminal glycine residues for the PGI- and PGII-type trimers and tetramers are all in very similar environments and that the glycine residues which are sandwiched between the two terminal residues are also in a similar environment for both the trimers and the tetramers.