| Spiral Superstructures of Amyloid-Like Fibrils of Polyglutamic Acid: An Infrared Absorption and Vibrational Circular Dichroism Study. | |
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MedLine Citation:
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PMID: 21842891 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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Amyloid fibrils, which are often associated with certain degenerative disorders, reveal a number of intriguing spectral properties. However, the relationship between the structure of fibrils and their optical traits remains poorly understood. Poly(L-glutamic) acid is a model polypeptide shown recently to form amyloid-like fibrils with an atypical infrared amide I' band at 1595 cm-1, which has been attributed to the presence of bifurcated hydrogen bonds coupling C=O and N-D groups of the main chains to glutamate side chains. Here we show that this unusual amide I' band is observed only for fibrils grown from pure enantiomers of the polypeptide, whereas fibrils precipitating from equimolar mixtures of poly(L-glutamic) and poly(D-glutamic) acids have amide I' bands at 1684 and 1612 cm-1, which are indicative of a typical intermolecular antiparallel beta-sheet. Pure enantiomers of polyglutamic acid form spirally-twisted superstructures whose handedness is correlated to the amino acid chirality, while fibrils prepared from the racemate do not form SEM-detectable mesoscopically ordered structures. Vibrational circular dichroism (VCD) spectra of beta-aggregates prepared from mixtures of all L or D polyglutamic acid in varying ratios indicate that the enhancement of VCD intensity correlates with the presence of the twisted superstructures. Our results demonstrate that both IR absorption and enhanced VCD are sensitive to subtle packing defects taking place within the compact structure of amyloid fibrils. |
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Authors:
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Aleksandra Fulara; Ahmed Lakhani; Slawomir Wojcik; Hanna Nieznanska; Timothy A Keiderling; Wojciech Dzwolak |
Publication Detail:
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Type: JOURNAL ARTICLE Date: 2011-8-15 |
Journal Detail:
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Title: The journal of physical chemistry. B Volume: - ISSN: 1520-5207 ISO Abbreviation: - Publication Date: 2011 Aug |
Date Detail:
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Created Date: 2011-8-16 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 101157530 Medline TA: J Phys Chem B Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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