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Models for the 3 10 ‐helix/coil, π‐helix/coil, and α‐helix/3 10 ‐helix/coil transitions in isolated peptides
Author(s) -
Rohl Carol A.,
Doig Andrew J.
Publication year - 1996
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1002/pro.5560050822
Subject(s) - helix (gastropod) , electromagnetic coil , triple helix , crystallography , alpha helix , hydrogen bond , chemistry , collagen helix , stereochemistry , molecule , circular dichroism , physics , ecology , organic chemistry , quantum mechanics , snail , biology
Models for the 3 10 ‐helix/coil and π‐helix/coil equilibria have been derived. The theory is based on classifying residues into helical or nonhelical (coil) conformations. Statistical weights are assigned to residues in a helical conformation with an associated helical hydrogen bond, a helical conformation with no hydrogen bond, an N‐cap position, a C‐cap position, or the reference coil conformation. The models for α‐helix formation and 3 10 ‐helix formation have also been combined to describe a three‐state equilibrium in which α‐helical, 3 10 ‐helical, and coil conformations are populated. The results are compared with the modified Lifson‐Roig theory for the α‐helix/coil equilibrium. The comparison accounts for the experimental observations that 3 10 ‐helices tend to be short and π‐helices are not favored for any length. This work may provide a framework for quantitatively rationalizing experimental work on isolated 3 10 ‐helices and mixed 3 10 ‐/α‐helices.