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UV-resonance Raman thermal unfolding study of Trp-cage shows that it is not a simple two-state miniprotein

Ahmed, Z and Beta, IA and Mikhonin, AV and Asher, SA (2005) UV-resonance Raman thermal unfolding study of Trp-cage shows that it is not a simple two-state miniprotein. Journal of the American Chemical Society, 127 (31). 10943 - 10950. ISSN 0002-7863

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Abstract

Trp-cage, a synthetic 20 residue polypeptide, is proposed to be an ultrafast folding synthetic miniprotein which utilizes tertiary contacts to define its native conformation. We utilized UV resonance Raman spectroscopy (UVRS) with 204 and 229 nm excitation to follow its thermal melting. Our results indicate that Trp-cage melting is complex, and it is not a simple two-state process. Using 204 nm excitation we probe the peptide secondary structure and find the Trp-cage's α-helix shows a broad melting curve where on average four α-helical amide bonds melt upon a temperature increase from 4 to 70 °C. Using 229 nm excitation we probe the environment of the Trp side chain and find that its immediate environment becomes more compact as the temperature is increased from 4 to 20 °C; however, further temperature increases lead to exposure of the Trp to water. The χ2 angle of the Trp side chain remains invariant throughout the entire temperature range. Previous kinetic results indicated a single-exponential decay in the 4-70 °C temperature range, suggesting that Trp-cage behaves as a two-state folder. However, this miniprotein does not show clear two-state behavior in our steady-state studies. Rather it shows a continuous distribution of steady-state spectral parameters. Only the α-helix melting curve even hints of a cooperative transition. Possibly, the previous kinetic results monitor only a small region of the Trp-cage which locally appears two-state. This would then argue for spatially decoupled folding even for this small peptide. © 2005 American Chemical Society.


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Details

Item Type: Article
Status: Published
Creators/Authors:
CreatorsEmailPitt UsernameORCID
Ahmed, Z
Beta, IA
Mikhonin, AV
Asher, SAasher@pitt.eduASHER
Date: 10 August 2005
Date Type: Publication
Journal or Publication Title: Journal of the American Chemical Society
Volume: 127
Number: 31
Page Range: 10943 - 10950
DOI or Unique Handle: 10.1021/ja050664e
Schools and Programs: Dietrich School of Arts and Sciences > Chemistry
Refereed: Yes
ISSN: 0002-7863
MeSH Headings: Amino Acid Sequence; Molecular Sequence Data; Peptides--chemistry; Proline--chemistry; Spectrum Analysis, Raman; Temperature; Ultraviolet Rays
PubMed ID: 16076200
Date Deposited: 08 Feb 2013 21:13
Last Modified: 02 Feb 2019 16:55
URI: http://d-scholarship.pitt.edu/id/eprint/17210

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