Fluorescence determination of tryptophan side-chain accessibility and dynamics in triple-helical collagen-like peptides |
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Authors: | Simon-Lukasik Kristine V Persikov Anton V Brodsky Barbara Ramshaw John A M Laws William R Alexander Ross J B Ludescher Richard D |
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Institution: | Department of Food Science, Rutgers University, New Brunswick, New Jersey 08901, USA. |
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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. |
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Keywords: | Hyp hydroxyproline GWO peptide with Trp at X site GPW peptide with Trp at Y site NATA N-acetyl-tryptophanamide |
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