VIBRATIONAL-SPECTRA OF N-ACETYLGLYCINE OLIGOMERS .2. RAMAN-SCATTERINGSTUDY OF SELECTIVELY C-DEUTERIATED OLIGOMERS WITH POLYGLYCINE-I-TYPE AND POLYGLYCINE-II-TYPE STRUCTURES

Selectively C-deuteriated N-acetylglycine trimer and tetramer acid typ es have been synthesized, and their two crystalline modifications, sol id-A and solid-B [which correspond in structure to polyglycine (PG) II and I, respectively] have been prepared. Raman scattering spectra hav e been measured for a series of these glycine oligomers, and the CH2- and CD2-characteristic modes have been investigated in detail. Assignm ent of the CH2-characteristic bands to each CH2 group in the oligomers has been carried out successfully. In particular, the results obtaine d from the CD2 stretch region show that N- and C-terminal glycine resi dues for the PGI- and PGII-type trimers and tetramers are all in very similar environments and that the glycine residues which are sandwiche d between the two terminal residues are also in a similar environment for both the trimers and the tetramers.