title: Fluorescence determination of tryptophan side-chain accessibility and dynamics in triple-helical collagen-like peptides.
abstract: We report tryptophan fluorescence measurements of emission intensity, iodide quenching, and anisotropy that describe the environment and dynamics at X and Y sites in stable collagen-like peptides of sequence (Gly-X-Y)(n). About 90% of tryptophans at both sites have similar solvent exposed fluorescence properties and a lifetime of 8.5-9 ns. Analysis of anisotropy decays using an associative model indicates that these long lifetime populations undergo rapid depolarizing motion with a 0.5 ns correlation time; however, the extent of fast motion at the Y site is considerably less than the essentially unrestricted motion at the X site. About 10% of tryptophans at both sites have a shorter ( approximately 3 ns) lifetime indicating proximity to a protein quenching group; these minor populations are immobile on the peptide surface, depolarizing only by overall trimer rotation. Iodide quenching indicates that tryptophans at the X site are more accessible to solvent. Side chains at X sites are more solvent accessible and considerably more mobile than residues at Y sites and can more readily fluctuate among alternate intermolecular interactions in collagen fibrils. This fluorescence analysis of collagen-like peptides lays a foundation for studies on the structure, dynamics, and function of collagen and of triple-helical junctions in gelatin gels.
authors.affiliation: Department of Food Science, Rutgers University, New Brunswick, New Jersey 08901, USA.
authors.forename: Kristine V
authors.initials: KV
authors.lastname: Simon-Lukasik
authors.forename: Anton V
authors.initials: AV
authors.lastname: Persikov
authors.forename: Barbara
authors.initials: B
authors.lastname: Brodsky
authors.forename: John A M
authors.initials: JA
authors.lastname: Ramshaw
authors.forename: William R
authors.initials: WR
authors.lastname: Laws
authors.forename: J B
authors.initials: JB
authors.lastname: Alexander Ross
authors.forename: Richard D
authors.initials: RD
authors.lastname: Ludescher
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003094:Collagen / Q000737:chemistry*; D005240:Feasibility Studies; D005454:Fluorescence Polarization / Q000379:methods*; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D013050:Spectrometry, Fluorescence / Q000379:methods*; D014364:Tryptophan / Q000737:chemistry
chemical_list: C475913:Ac-(Gly-Pro-Hyp)3-Gly-Pro-Trp-(Gly-Pro-Hyp)4-Gly-Gly-CONH2; C475912:Ac-(Gly-Pro-Hyp)3-Gly-Trp-Hyp-(Gly-Pro-Hyp)4-Gly-Gly-CONH2; D010455:Peptides; D014364:Tryptophan; D003094:Collagen