title: IR study of cross-strand coupling in a beta-hairpin peptide using isotopic labels.
abstract: Model beta-hairpin peptides can be used to develop understanding of fundamental elements of beta-sheet secondary structure formation and stability. We have studied two 13C-labeled variants of a beta-hairpin peptide modified from a design originally proposed by Gellman: Arg-Tyr-Val-Glu-Val-Aib-Gly-Lys-Lys-Ile-Leu-Gln. (In this peptide, the two italicized residues form a beta-turn, while 13C-labels are on the amide C=O of Val3, Lys8 in HBG-L and Val3, Ile10 in HBG-S.) Both these peptides are labeled on opposite strands of the hairpin, but differ in the labeling pattern. One (HBG-L) forms a large (14-atom) H-bonded ring of labeled C=Os, while the other (HBG-S) forms a small (10-atom) H-bonded ring. These impact the amide I infrared spectra, with HBG-L having a 13C frequency and intensity higher than that of HBG-S, in good agreement with our spectral simulations based on quantum mechanically derived force fields. The thermal behavior of both peptides yields a broad thermal transition and lacks an isosbestic point. The 13C band for HBG-L has the largest intensity change with temperature, distinct from the 12C change and the HBG-S 13C change.
authors.affiliation: Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607-7061, USA.
authors.forename: Vladimír
authors.initials: V
authors.lastname: Setnicka
authors.forename: Rong
authors.initials: R
authors.lastname: Huang
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Thomas
authors.forename: Marcus A
authors.initials: MA
authors.lastname: Etienne
authors.forename: Jan
authors.initials: J
authors.lastname: Kubelka
authors.forename: Robert P
authors.initials: RP
authors.lastname: Hammer
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Keiderling
mesh_terms: D000595:Amino Acid Sequence; D000621:Aminoisobutyric Acids / Q000737:chemistry; D005998:Glycine / Q000737:chemistry; D006860:Hydrogen Bonding; D009842:Oligopeptides / Q000737:chemistry*; D011392:Proline / Q000737:chemistry; D011487:Protein Conformation; D017510:Protein Folding; D013055:Spectrophotometry, Infrared / Q000379:methods
chemical_list: D000621:Aminoisobutyric Acids; D009842:Oligopeptides; D011392:Proline; D005998:Glycine