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Uncoupled peptide bond vibrations in α-helical and polyproline II conformations of tolyalanine peptides

Mikhonin, AV and Asher, SA (2005) Uncoupled peptide bond vibrations in α-helical and polyproline II conformations of tolyalanine peptides. Journal of Physical Chemistry B, 109 (7). 3047 - 3052. ISSN 1520-6106

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We examined the 204-nm UV resonance Raman (UVR) spectra of the polyproline II (PPII) and α-helical states of a 21-residue mainly alanine peptide (AP) in different H 2O/D 2O mixtures. Our hypothesis is that if the amide backbone vibrations are coupled, then partial deuteration of the amide N will perturb the amide frequencies and Raman cross sections since the coupling will be interrupted; the spectra of the partially deuterated derivatives will not simply be the sum of the fully protonated and deuterated peptides. We find that the UVR spectra of the AmIII and AmII′ bands of both the PPII conformation and the α-helical conformation (and also the PPII AmI, AmI′, and AmII bands) can be exactly modeled as the linear sum of the fully N-H protonated and N-D deuterated peptides. Negligible coupling occurs for these vibrations between adjacent peptide bonds. Thus, we conclude that these peptide bond Raman bands can be considered as being independently Raman scattered by the individual peptide bonds. This dramatically simplifies the use of these vibrational bands in IR and Raman studies of peptide and protein structure. In contrast, the AmI and AmI′ bands of the α-helical conformation cannot be well modeled as a linear sum of the fully N-H protonated and N-D deuterated derivatives. These bands show evidence of coupling between adjacent peptide bond vibrations. Care must be taken in utilizing the AmI and AmI′ bands for monitoring α-helical conformations since these bands are likely to change as the α-helical length changes and the backbone conformation is perturbed. © 2005 American Chemical Society.


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Item Type: Article
Status: Published
CreatorsEmailPitt UsernameORCID
Mikhonin, AV
Asher, SAasher@pitt.eduASHER
Date: 24 February 2005
Date Type: Publication
Journal or Publication Title: Journal of Physical Chemistry B
Volume: 109
Number: 7
Page Range: 3047 - 3052
DOI or Unique Handle: 10.1021/jp0460442
Schools and Programs: Dietrich School of Arts and Sciences > Chemistry
Refereed: Yes
ISSN: 1520-6106
MeSH Headings: Amides--chemistry; Chemistry, Physical--methods; Deuterium Oxide--chemistry; Molecular Conformation; Peptides--chemistry; Protein Conformation; Protein Structure, Secondary; Spectrophotometry, Infrared; Spectrophotometry, Ultraviolet; Spectrum Analysis, Raman; Ultraviolet Rays; Water--chemistry
PubMed ID: 16851319
Date Deposited: 08 Feb 2013 21:15
Last Modified: 22 Jun 2021 13:55


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