Far‐infrared spectra of polyalanines with α‐helical and β‐form structures

Abstract

SynopsisFar-infrared spectra of poly-palanines having the a-helical conformation and the ,%form structure were measured. The spectra of glycine-L-alanine copolymer, silk fibroin, and copoly-D,calanines with different D : L compositions were also measured. In addition to the bands so far reported, four bands at 190, 167, 120, and 90 cm-1 were found for the a-helix conformation and the two bands at 442 and 247 cm-1 were found for the 6 form. The 442 cm-l band consists of the parallel 432 cm-l and perpendicular 445 cm-1 bands. The 247 cm-1 band is well defined and has strong dichroism parallel to the direction of stretching. These two bands appear also for silk fibroin and glycine-L-alanine copolymer. All the far-infrared bands of copoly-D,talanines can be interpreted as a-helix bands, the three peaks at 580, 478, and 420 cm-I being ascribed to the D-residue incorporated into the right-handed a-helix or to the tresidue in the left-handed a-helix.

Silk: Optical Properties over 12.6 Octaves THz-IR-Visible-UV Range

“…However, for B. mori silk, in addition to the dominant 243 cm${}^{-1}$ absorption band, three other peaks at 335, 427, and 546 cm${}^{-1}$ can be discerned, especially for heat-treated samples with reduced water content. Four bands have been previously observed in a similar spectral vicinity at 250, 328, 427, and 553 cm${}^{-1}$, respectively, for $\beta$-sheet rich fibroin films [39]. In contrast, A. pernyi silk fibers have far-IR absorbance spectra with two discernible peaks—at 229 and 439 cm${}^{-1}$.…”

A HIGH RESOLUTION 13C NMR STUDY OF SOLID POLY (β-BENZYL-l-ASPARTATE) BY THE CROSS POLARIZATION-MAGIC ANGLE SPINNING METHOD. DISTINCTION OF THE RIGHT-HANDED α-HELIX, LEFT-HANDED α-HELIX, ω-HELIX, AND β-SHEET FORMS BY CONFORMATION-DEPENDENT 13C CHEMICAL SHIFTS

“…23) In consistent with this view, we showed that the 13C chemical shifts of D-and Lalanine residues in the copolymers are well reproduced by the calculated contour map of 13C chemical shifts of N-acetyl N'-methyl-L-alanine amide as a model of (Ala) utilizing the FPT-INDO method. 7) In contrast, it was difficult to explain the changes of '3C chemical shifts by the concept of the y-effect.…”

Low frequency vibrations of amino acid homopolymers observed by synchrotron far-ir absorption spectroscopy: Excited state effects dominate the temperature dependence of the spectra

“…17 . Our data ( Figure 1 and Table I) confirm these observations, but illustrate the richness of the spectrum and the numerous ir active modes present in this molecule.…”