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Direct UV Raman monitoring of 3<inf>10</inf>-helix and π-bulge premelting during α-helix unfolding

Mikhonin, AV and Asher, SA (2006) Direct UV Raman monitoring of 3<inf>10</inf>-helix and π-bulge premelting during α-helix unfolding. Journal of the American Chemical Society, 128 (42). 13789 - 13795. ISSN 0002-7863

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Abstract

We used UV resonance Raman (UVRR) spectroscopy exciting at ∼200 nm within the peptide bond π→π* transitions to selectively study the amide vibrations of peptide bonds during α-helix melting. The dependence of the amide frequencies on their Ψ Ramachandran angles and hydrogen bonding enables us, for the first time, to experimentally determine the temperature dependence of the peptide bond Ψ Ramachandran angle population distribution of a 21-residue mainly alanine peptide. These Ψ distributions allow us to easily discriminate between α-helix, 310-helix and α-helix/bulge conformations, obtain their individual melting curves, and estimate the corresponding Zimm and Bragg parameters. A striking finding is that α-helix melting is more cooperative and shows a higher melting temperature than previously erroneously observed. These Ψ distributions also enable the experimental determination of the Gibbs free energy landscape along the Ψ reaction coordinate, which further allows us to estimate the free energy barriers along the AP melting pathway. These results will serve as a benchmark for the numerous untested theoretical studies of protein and peptide folding. © 2006 American Chemical Society.


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Details

Item Type: Article
Status: Published
Creators/Authors:
CreatorsEmailPitt UsernameORCID
Mikhonin, AV
Asher, SAasher@pitt.eduASHER
Date: 25 October 2006
Date Type: Publication
Journal or Publication Title: Journal of the American Chemical Society
Volume: 128
Number: 42
Page Range: 13789 - 13795
DOI or Unique Handle: 10.1021/ja062269+
Schools and Programs: Dietrich School of Arts and Sciences > Chemistry
Refereed: Yes
ISSN: 0002-7863
MeSH Headings: Amides--chemistry; Hydrogen Bonding; Peptides--chemistry; Protein Folding; Protein Structure, Secondary; Proteins--chemistry; Spectrophotometry, Ultraviolet; Spectrum Analysis, Raman; Thermodynamics
PubMed ID: 17044707
Date Deposited: 08 Feb 2013 21:13
Last Modified: 02 Feb 2019 16:55
URI: http://d-scholarship.pitt.edu/id/eprint/17211

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