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Vibrational analysis of peptides, polypeptides, and proteins. XVIII. Conformational sensitivity of the α‐helix spectrum: α I ‐ and α II ‐Poly( L ‐alanine)
Author(s) -
Dwivedi Anil M.,
Krimm S.
Publication year - 1984
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360230509
Subject(s) - bacteriorhodopsin , chemistry , helix (gastropod) , amide , crystallography , alanine , alpha helix , amino acid , circular dichroism , biochemistry , membrane , biology , ecology , snail
The α II ‐helix (ϕ = −70.47°, ψ = −35.75°) is a structure having the same n and h as the (standard) α I ‐helix (ϕ = −57.37°, ψ = −47.49°). Its conformational angles are commonly found in proteins. Using an improved α‐helix force field, we have compared the vibrational frequencies of these two structures. Despite the small conformational differences, there are significant predicted differences in frequencies, particularly in the amide A, amide I, and amide II bands, and in the conformation‐sensitive region below 900 cm −1 . This analysis indicates that α II ‐helices are likely to be present in bacteriorhodopsin [Krimm, S. & Dwivedi, A. M. (1982) Science 216 , 407–408].