eprintid: 17176 rev_number: 24 userid: 1419 dir: disk0/00/01/71/76 datestamp: 2013-02-08 21:21:13 lastmod: 2021-06-12 23:55:35 status_changed: 2013-02-08 21:21:13 type: article metadata_visibility: show item_issues_count: 0 eprint_status: archive creators_name: Asher, SA creators_name: Mikhonin, AV creators_name: Bykov, S creators_email: asher@pitt.edu creators_email: creators_email: creators_id: ASHER creators_id: creators_id: title: UV Raman demonstrates that α-helical polyalanine peptides melt to polyproline II conformations ispublished: pub divisions: sch_as_chemistry full_text_status: public abstract: We examined the 204-nm UV Raman spectra of the peptide XAO, which was previously found by Shi et al.'s NMR study to occur in aqueous solution in a polyproline II (PPII) conformation (Proc. Natl. Acad. Sci. U.S.A. 2002, 99, 9190). The UV Raman spectra of XAO are essentially identical to the spectra of small peptides such as ala5 and to the large 21 -residue predominantly Ala peptide, AP. We conclude that the non-α-helical conformations of these peptides are dominantly PPII. Thus, AP, which is highly α-helical at room temperature, melts to a PPII conformation. There is no indication of any population of intermediate disordered conformations. We continued our development of methods to relate the Ramachandran ψ-angle to the amide III band frequency. We describe a new method to estimate the Ramachandran ψ-angular distributions from amide III band line shapes measured in 204-nm UV Raman spectra. We used this method to compare the ψ-distributions in XAO, ala5, the non-α-helical state of AP, and acid-denatured apomyoglobin. In addition, we estimated the ψ-angle distributions of peptide bonds which occur in non-α-helix and non-β-sheet conformations in a small library of proteins. date: 2004-07-14 date_type: published publication: Journal of the American Chemical Society volume: 126 number: 27 pagerange: 8433 - 8440 refereed: TRUE issn: 0002-7863 id_number: 10.1021/ja049518j pmid: 15238000 mesh_headings: Amides--chemistry mesh_headings: Chemistry, Physical mesh_headings: Peptides--chemistry mesh_headings: Physicochemical Phenomena mesh_headings: Protein Conformation mesh_headings: Protein Structure, Secondary mesh_headings: Spectrophotometry, Ultraviolet mesh_headings: Spectrum Analysis, Raman--methods mesh_headings: Temperature chemical_names: Amides chemical_names: Peptides chemical_names: polyproline chemical_names: polyalanine citation: Asher, SA and Mikhonin, AV and Bykov, S (2004) UV Raman demonstrates that α-helical polyalanine peptides melt to polyproline II conformations. Journal of the American Chemical Society, 126 (27). 8433 - 8440. ISSN 0002-7863 document_url: http://d-scholarship-dev.library.pitt.edu/17176/1/licence.txt