Molecular velocity auto-correlations in glycerol/water mixtures studied by NMR MGSE method

TL;DR

This study uses NMR MGSE to analyze water molecule velocity auto-correlations in glycerol/water mixtures, revealing heterogeneity and interaction effects that influence molecular motion and potential protein folding.

Contribution

It introduces a novel NMR MGSE approach to investigate molecular dynamics and heterogeneity in glycerol/water mixtures across a wide frequency range.

Findings

Heterogeneity of molecular motion varies with glycerol concentration.

Water molecules form clusters around glycerol, affecting diffusion spectra.

Increased glycerol leads to slower molecular motions and potential protein folding conditions.

Abstract

Molecular dynamics in binary mixtures of water and glycerol was studied by measuring the spectrum of water velocity auto-correlation in the frequency range from 0.05 to 10 kHz by using the NMR method of modulated gradient spin echo. The method shows that the diversity of diffusion signature in the short spin trajectories provides information about heterogeneity of molecular motion due to the motion in the micro-vortexes of hydrodynamic fluctuation, which is especially pronounced for the mixtures with the low glycerol content. As concentration of glycerol increases above 10vol%, a new feature of spectrum appears due to interaction of water molecules with the clusters formed around hydrophilic glycerol molecules. New spectrum exposes a rate thickening of molecular friction, according to Einstein-Smoluchowski-Kubo formula, which inhibits rapid molecular motions and creates the conditions for a slow process of spontaneously folding of disordered poly-peptides into biologically active protein molecules when immersed in such a mixture.