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Ultraviolet resonance Raman study of side chain electrostatic control of poly-l-lysine conformation

Ma, L and Ahmed, Z and Asher, SA (2011) Ultraviolet resonance Raman study of side chain electrostatic control of poly-l-lysine conformation. Journal of Physical Chemistry B, 115 (14). 4251 - 4258. ISSN 1520-6106

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Abstract

We used 204 nm excitation UV resonance Raman (UVRR) spectroscopy to examine the role of side chain electrostatic interactions in determining the conformation of poly-l-lysine (PLL). We examined the pH and ionic strength dependence of the UVRR. The pH dependence of PLL UVRR spectra between pH 7.1 and 11.7 cannot be described by a two-state model but requires at least one additional state. The AmIII3 region fitting with pH 7.1 and 11.7 basis spectra reveals a small pH-induced decrease in the relative fraction of the 2.51-helix conformation compared to the PPII conformation. We performed a 2D general correlation analysis on the PLL pH dependence UVRR spectra. The asynchronous spectrum shows enhanced spectral resolution. The 2D asynchronous spectrum reveals multiple components in the Cα-H b band and the AmII band whose origins are unclear. The cross peaks in the 2D asynchronous spectrum between the AmIII band and the other bands reveals that increasing pH induces three new structures: π-helix, α-helix, and some turn structure. We find that 2.5 M NaCl does not change the equilibrium between the PPII and 2.51-helix conformations by screening side chain electrostatic repulsion. The result indicates that NaCl does not penetrate the region between the side chain and the peptide backbone. We also compared PLL conformations induced by high pH to that induced by 0.8 M ClO4-. Both conditions induce α-helix-like conformations. ClO 4- (0.8 M) induces 6% more α-helix-like conformations than at pH 12.4. Higher pH gives rise to longer α-helices and less turn structures. © 2011 American Chemical Society.


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Details

Item Type: Article
Status: Published
Creators/Authors:
CreatorsEmailPitt UsernameORCID
Ma, L
Ahmed, Z
Asher, SAasher@pitt.eduASHER
Date: 14 April 2011
Date Type: Publication
Journal or Publication Title: Journal of Physical Chemistry B
Volume: 115
Number: 14
Page Range: 4251 - 4258
DOI or Unique Handle: 10.1021/jp2005343
Schools and Programs: Dietrich School of Arts and Sciences > Chemistry
Refereed: Yes
ISSN: 1520-6106
MeSH Headings: Hydrogen-Ion Concentration; Osmolar Concentration; Polylysine--chemistry; Protein Structure, Secondary; Sodium Chloride--chemistry; Spectrum Analysis, Raman; Static Electricity; Ultraviolet Rays
Other ID: NLM NIHMS281795, NLM PMC3072461
PubMed Central ID: PMC3072461
PubMed ID: 21413713
Date Deposited: 08 Feb 2013 20:47
Last Modified: 22 Jun 2021 13:55
URI: http://d-scholarship.pitt.edu/id/eprint/17278

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