Y. Imanishi, Kazuya Kugimiya, T. Higashimura
May 1, 1975
Citations
0
Influential Citations
3
Citations
Journal
Polymer
Abstract
Abstract Nuclear magnetic resonance (n.m.r.) and circular dichroism of poly (N- methyl- l -alanine ) in methylene chloride -d 2 dichloroacetic acid were investigated. In methylene chloride-d2 poly (N- methyl- l -alanine ) was found to consist of nearly all-trans amide bonds and assume a stable secondary structure. Trace amounts of cis amide bonds were also present. The addition of dichloroacetic acid destroyed the secondary structure and induced a drastic change of the n.m.r. spectrum, which was similar to that observed with the monomeric amide, N- acetyl -N- methyl- l -alanine dimethylamide. In comparison of the polymer with the monomeric amide, it was concluded that the transition of poly (N- methyl- l -alanine ) was caused by the isomerization of amide bonds. The complex n.m.r. spectrum was interpreted in terms of the distribution along the polymer chain of various non-planar amide links as well as planar cis and trans amide links. The difference of the mechanism of conformational transition between poly(amino acid) and poly(imino acid) is also discussed.