title: Position-dependent local motions in spin-labeled analogues of a short alpha-helical peptide determined by electron spin resonance.
abstract: We have used electron spin resonance and circular dichroism to examine and compare the dynamics in two analogues of the Ala-based 3K(I) peptide [Marqusee, S., Robbins, V.H., & Baldwin, R. L. (1989) Proc. Natl. Acad. Sci. U.S.A. 86, 5286-5290], labeled at positions 4 and 8, throughout the alpha-helix----coil transition. In the middle of the thermal unfolding transition, our results demonstrate that the local mobility near the N-terminus is greater than at the center of the peptide. This provides evidence, from the perspective of dynamics, that the ends of Ala-based alpha-helices are frayed. We further find that the position dependence of the mobility for the thermally unfolded state differs from that of the denaturant unfolded state. Only the latter state exhibits the local dynamics expected for a genuine random coil.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Cruz 95064.
authors.forename: S M
authors.initials: SM
authors.lastname: Miick
authors.forename: A P
authors.initials: AP
authors.lastname: Todd
authors.forename: G L
authors.initials: GL
authors.lastname: Millhauser
mesh_terms: D000409:Alanine / Q000737:chemistry; D000595:Amino Acid Sequence; D002942:Circular Dichroism; D004578:Electron Spin Resonance Spectroscopy; D005998:Glycine / Q000737:chemistry; D008969:Molecular Sequence Data; D009038:Motion; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry*; D011487:Protein Conformation; D013329:Structure-Activity Relationship; D013696:Temperature
chemical_list: D010455:Peptides; D000409:Alanine; D005998:Glycine