eprintid: 17219 rev_number: 22 userid: 1419 dir: disk0/00/01/72/19 datestamp: 2013-02-08 21:07:15 lastmod: 2021-06-12 23:55:16 status_changed: 2013-02-08 21:07:15 type: article metadata_visibility: show item_issues_count: 0 eprint_status: archive creators_name: Mikhonin, AV creators_name: Asher, SA creators_name: Bykov, SV creators_name: Murza, A creators_email: creators_email: asher@pitt.edu creators_email: creators_email: creators_id: creators_id: ASHER creators_id: creators_id: title: UV Raman spatially resolved melting dynamics of isotopically labeled polyalanyl peptide: Slow α-helix melting follows 310-helices and π-bulges premelting ispublished: pub divisions: sch_as_chemistry full_text_status: public abstract: We used UV resonance Raman (UVRR) to examine the spatial dependence of the T-jump secondary structure relaxation of an isotopically labeled 21-residue mainly Ala peptide, AdP. The AdP penultimate Ala residues were perdeuterated, leaving the central residues hydrogenated, to allow separate monitoring of melting of the middle versus the end peptide bonds. For 5 to 30°C T-jumps, the central peptide bonds show a ∑2-fold slower relaxation time (189 ± 31 ns) than do the exterior peptide bonds (97 ± 15 ns). In contrast, for a 20 to 40°C T-jump, the central peptide bond relaxation appears to be faster (56 ± 6 ns) than that of the penultimate peptide bonds (131 ± 46 ns). We show that, if the data are modeled as a two-state transition, we find that only exterior peptide bonds show anti-Arrhenius folding behavior; the middle peptide bonds show both normal Arrhenius-like folding and unfolding. This anti-Arrhenius behavior results from the involvement of π-bulges/helices and 310-helix states in the melting. The unusual temperature dependence of the (un)folding rates of the interior and exterior peptide bonds is due to the different relative (un)folding rates of 310-helices, α-helices, and π-bulges/helices. Pure α-helix unfolding rates are ∼12-fold slower (∼1 μs) than that of π-bulges and 310-helices. In addition, we also find that the α-helix is most stable at the AdP N-terminus where eight consecutive Ala occur, whereas the three hydrophilic. Arg located in the middle and at the C-terminus destabilize the α-helix in these regions and induce defects such as π-bulges and 310-helices. © 2007 American Chemical Society. date: 2007-03-29 date_type: published publication: Journal of Physical Chemistry B volume: 111 number: 12 pagerange: 3280 - 3292 refereed: TRUE issn: 1520-6106 id_number: 10.1021/jp0654009 pmid: 17388440 mesh_headings: Algorithms mesh_headings: Chemistry, Physical mesh_headings: Kinetics mesh_headings: Models, Chemical mesh_headings: Nonlinear Dynamics mesh_headings: Peptides--chemistry mesh_headings: Physicochemical Phenomena mesh_headings: Protein Folding mesh_headings: Protein Structure, Secondary mesh_headings: Spectrophotometry, Ultraviolet mesh_headings: Spectrum Analysis, Raman mesh_headings: Thermodynamics chemical_names: Peptides chemical_names: polyalanine citation: Mikhonin, AV and Asher, SA and Bykov, SV and Murza, A (2007) UV Raman spatially resolved melting dynamics of isotopically labeled polyalanyl peptide: Slow α-helix melting follows 310-helices and π-bulges premelting. Journal of Physical Chemistry B, 111 (12). 3280 - 3292. ISSN 1520-6106 document_url: http://d-scholarship-dev.library.pitt.edu/17219/1/licence.txt