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Laser-Raman spectroscopy of biomolecules. XI. Conformational study of poly(L-valine) and copolymers of L-valine and L-alanine

✍ Scribed by Gerald D. Fasman; Koichi Itoh; Christopher S. Liu; Richard C. Lord

Publisher
Wiley (John Wiley & Sons)
Year
1978
Tongue
English
Weight
940 KB
Volume
17
Category
Article
ISSN
0006-3525

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✦ Synopsis

Abstract

Raman spectroscopic studies have been carried out on polymers of L‐valine ranging in degree of polymerization (DP) from 2 to 930. The spectrum of the hexapeptide (DP = 6) is closely similar over the entire range 40–1750 cm^−1^ to those of polymers with much higher DP, and the structure is clearly shown to be that of the antiparallel pleated sheet (β‐structure) by the amide I and III frequencies. The formation of a little α‐helical structure occurs in polymers with DP above 500, although the amount does not appear to be a linear function of DP. The α‐helical structure is unstable and readily destroyed in samples cast from trifluoroacetic acid solution. It is stabilized by the incorporation of L‐alanine, a strong helix‐former; polymers of the latter may in turn be forced into a α‐structure in copolymers sufficiently rich in L‐valine.

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