Observing the Hydration Layer of Trehalose with a Linked Molecular Terahertz Probe

The terahertz (THz) absorption bands of biomolecular hydration layers are generally swamped by absorption from bulk water. Using the disaccharide trehalose, we show that this limitation can be overcome by attaching a molecular probe. By time-resolving the fluorescence shift of the probe, a local THz spectrum is obtained. From the dependence on temperature and H₂O/D₂O exchange, it is concluded that the trehalose hydration layer is being observed. The region of dynamic water perturbation by the disaccharide encompasses the probe and is therefore larger than the first two solvation layers

Effect of a Tertiary Butyl Group on Polar Solvation Dynamics in Aqueous Solution: Femtosecond Fluorescence Spectroscopy

We monitor the time-dependent Stokes shift (TDSS) of fluorescence from the zwitterionic probe <i>N</i>-methyl-6-oxyquinolinium betaine in water. A spectral relaxation time τ_solv = 0.57 ps (at 20.5 °C) is attributed to a solvation process involving water in the hydration layer. In this article we show that a tertiary butyl group, when attached to the chromophore, slows the dynamics to τ_solv = 0.76 ps and increases the corresponding activation energy by 5 kJ/mol. In a companion paper (10.1021/acs.jpcb.7b05039), simulations suggest that the observed slow-down indicates coupling of solute vibrations to hydration water. Thus, a new angle on a thoroughly researched topic, solvation dynamics, has been opened

Caracterisation en bande large du canal radio-mobile en milieu urbain

CNRS RP 256 (20) / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc