FAR-INFRARED SPECTRA OF POLY(-ALPHA-AMINO ACIDS) WITH BASIC ALKYL GROUP SIDE CHAINS

Far‐infrared spectra in the region from 700 to 60 cm−1 have been measured for the α‐helix structures of poly(L‐α‐amino‐n‐butyric acid), poly‐L‐norvaline, poly‐L‐norleucine, and poly‐L‐leucine and for the β‐form structures of poly(L‐α‐amino‐n‐butyric acid), poly‐L‐valine, poly(DL‐amino‐n‐butyric acid), poly‐DL‐norvaline, and poly‐DL‐norleucine. The changes of the spectra on N‐deuteration have been measured in the region between 700 and 400 cm−1. It is concluded that, the α‐helix has characteristic bauds near 690, 650, 610, 380, 150, and 100 cm−1, and that the β‐form has characteristic bands near 700, 240, and 120 cm−1. The main‐chain vibrations in the region from 600 to 200 cm−1 are strongly coupled with the side‐chain deformation vibrations. Copyright © 1969 John Wiley & Sons, Inc.