화학공학소재연구정보센터
Journal of Physical Chemistry B, Vol.116, No.1, 555-564, 2012
Thermal Hysteresis in the Backbone and Side-Chain Dynamics of the Elastin Mimetic Peptide [VPGVG](3) by H-2 NMR
We report on experimental measurements of the backbone and side-chain dynamics of the elastin mimetic peptide [VPGVG](3) by H-2 NMR echo spectroscopy and 2D T-1-T-2 correlation relaxometry. The T-1 and T-2 relaxation times of the Gly alpha-deuterons and Val alpha-, beta-, and gamma-deuterons of a hydrated sample reveal a thermal hysteresis when the temperature is raised from -10 to 45 degrees C and then subsequently cooled back to -10 degrees C. In addition, near 30 degrees 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 alpha-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 degrees C.