title: Thermal hysteresis in the backbone and side-chain dynamics of the elastin mimetic peptide [VPGVG]3 revealed by 2H NMR.
abstract: We report on experimental measurements of the backbone and side-chain dynamics of the elastin mimetic peptide [VPGVG](3) by (2)H NMR echo spectroscopy and 2D T(1)-T(2) correlation relaxometry. The T(1) and T(2) relaxation times of the Gly α-deuterons and Val α-, β-, and γ-deuterons of a hydrated sample reveal a thermal hysteresis when the temperature is raised from -10 to 45 °C and then subsequently cooled back to -10 °C. In addition, near 30 °C we observe a reduction in the slope of the T(1)(T) and T(2)(T) heating curves, indicating a structural change that appears to be correlated well to the known inverse temperature transition of this peptide. The thermal dependence of the correlation times of the Gly α-deuterons are well fit by an Arrhenius Law, from which we measured E(act) = (20.0 ± 3.1) kJ/mol when the sample is heated and E(act) = (10.9 ± 2.8) kJ/mol when cooled. Molecular dynamics simulations support the notion that the measured activation energy is determined largely by the extent of localized water, which is observed to decrease with increasing temperature from approximately 25 to 42 °C.
authors.affiliation: Department of Physics, Brooklyn College of the City University of New York, Brooklyn, New York 11210, United States.
authors.forename: Xiang
authors.initials: X
authors.lastname: Ma
authors.forename: Cheng
authors.initials: C
authors.lastname: Sun
authors.forename: Jiaxin
authors.initials: J
authors.lastname: Huang
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Boutis
mesh_terms: D004549:Elastin / Q000737:chemistry; D056004:Molecular Dynamics Simulation; D019906:Nuclear Magnetic Resonance, Biomolecular; D009842:Oligopeptides / Q000737:chemistry*; D044367:Phase Transition; D044366:Transition Temperature; D014867:Water / Q000737:chemistry
chemical_list: D009842:Oligopeptides; D014867:Water; C094883:valyl-prolyl-glycyl-valyl-glycine; D004549:Elastin