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Predicted and trifluoroethanol‐induced α‐helicity of polypeptides
Author(s) -
Luidens Mary Koeppe,
Figge James,
Breese Kimberly,
Vajda Sandor
Publication year - 1996
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/(sici)1097-0282(199609)39:3<367::aid-bip8>3.0.co;2-m
Subject(s) - chemistry , helicity , crystallography , protein secondary structure , solvent , circular dichroism , helix (gastropod) , monte carlo method , spectroscopy , spectral line , titration , physics , organic chemistry , biochemistry , ecology , statistics , mathematics , particle physics , quantum mechanics , astronomy , snail , biology
The α‐helix stabilizing solvent 2,2,2‐trifluoroethanol (TFE) is frequently used as a medium for determining the average α‐helicity of polypeptides by CD spectroscopy. CD spectra measured in solutions containing 10, 15, 20, 50, and 90% (vol/vol) TFE are presented for 5 peptides that were selected to demonstrate possible variations in the effect of TFE concentration on the secondary structure. The analysis is extended to 6 further peptides whose CD spectra as measured in TFE are documented in the literature. The observed α‐helicity at a high TFE concentration is compared with the α‐helicity determined by a structure prediction method that combines conformational filtering [S. Vajda, (1993) Journal of Molecular Biology , Vol. 229, pp. 125–145], and a Monte Carlo simulation [J. Figge et al. (1993) Protein Science , Vol. 2, pp. 155 –164]. For the set of 11 peptides we find a correlation of 0.84 between the predicted [θ] 222 values and the corresponding values observed by CD spectroscopy in a high concentration of TFE ( p < 0.01). Although we generally find a good correlation at high TFE concentration between observed and predicted α‐helicity, there are several peptides that do not follow the predicted behavior. An analysis of the TFE titration curves in one such case revealed that TFE can induce a sharp transition from a partial β‐sheet conformation to an α‐helical conformation as the TFE concentration is increased above a critical value. © 1996 John Wiley & Sons, Inc.