| Side-chain dynamics of an alpha-helical polypeptide monitored by fluorescence. | |
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MedLine Citation:
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PMID: 14558829 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The "blob" model, developed to analyze the fluorescence decays of polymers randomly labeled with pyrene, has been applied to a series of pyrene-labeled poly(glutamic acid)s (PyPGA) in DMF and carbonated buffer solutions at pH 9. Poly(glutamic acid) (PGA) exists in the ionized form in the buffer solutions as poly(sodium glutamate) (PGNa). PGA adopts an alpha-helical conformation in DMF, whereas in aqueous solution PGNa is a random coil. Fluorescence, UV-vis absorption, and circular dichroism measurements indicate that in our studies pyrene pendants attached themselves along PGA in a clustered manner. Simulations were carried out to establish that the geometry of the PGA alpha-helix induces the high level of pyrene clustering. Since the level of pyrene clustering decreased with lower pyrene content, information about naked PGA was retrieved by extrapolating the trends obtained by fluorescence to zero pyrene content. Analysis of the fluorescence decays demonstrated that during its lifetime an excited pyrene probes a 32 amino acid section of the PGA alpha-helix. This result was supported by molecular mechanics optimizations. This study establishes that the blob model, originally used to monitor the encounters between pyrenes attached randomly onto a polymer adopting a random coil conformation, can also be applied to study the dynamics of the side chains of structured proteins. Since the blob model helps in monitoring the encounters between amino acids in the initial state (i.e., random coil) and in the final state (i.e., structured protein) of the folding pathway of a protein, it could be applicable to the study of protein folding. |
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Authors:
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Jean Duhamel; Sabesh Kanagalingam; Thomas J O'Brien; Mark W Ingratta |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: Journal of the American Chemical Society Volume: 125 ISSN: 0002-7863 ISO Abbreviation: J. Am. Chem. Soc. Publication Date: 2003 Oct |
Date Detail:
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Created Date: 2003-10-15 Completed Date: 2003-12-17 Revised Date: 2006-11-15 |
Medline Journal Info:
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Nlm Unique ID: 7503056 Medline TA: J Am Chem Soc Country: United States |
Other Details:
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Languages: eng Pagination: 12810-22 Citation Subset: IM |
Affiliation:
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Institute for Polymer Research, Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, ON, N2L 3G1, Canada. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Circular Dichroism Dimethylformamide / chemistry Fluorescence Methylamines / chemistry Models, Chemical Polyglutamic Acid / analogs & derivatives*, chemistry Protein Conformation Protein Folding Protein Structure, Secondary Pyrenes / chemistry* Spectrometry, Fluorescence / methods |
| Chemical | |
Reg. No./Substance:
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0/Methylamines; 0/Pyrenes; 25513-46-6/Polyglutamic Acid; 68-12-2/Dimethylformamide |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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