Molecular Interactions in Heterogeneous Environments

Crowding disrupts solvent hydrogen bond networks and modulates the hydration levels of biomolecules and osmolytes. Although the effect of additives on biomolecular structure and stability has been extensively studied, the role of crowding and heterogeneity is not well understood. Dimethyl sulfoxide (DMSO) is important small organic solvent in adaptable applications, such as protein destabilization, cryopreservation, and drug permeation. In particular, DMSO disrupts the hydrogen-bond networks of water in DMSO/water binary mixtures. Here, vibrational spectroscopy combined with molecular dynamics simulations (MD) and quantum chemistry models was used to describe the mechanism by which H-bond interactions of DMSO/water mixtures and crowding effects on these heterogeneous systems. Based on directly quantifying H-bond populations using the S=O stretching vibration of DMSO, we show that crowding stabilizes hydrogen bonding in aqueous DMSO. Specifically, we use formamide and dimethylformamide (DMF) as molecular crowder, and map hydrogen bond populations of the S=O and C=O groups in DMSO/water/formamide or DMF ternary mixtures. Further, we use C=O stretching vibrations of formamide and DMF with 2D IR spectroscopy to quantify H-bond solvation dynamics in DMSO/water binary mixtures. Probe dependent solvation dynamics exhibit local clustering of DMSO/water binary mixtures. The results are as follows; 1. hydrogen bonds are formed and broken through a “step-in” mechanism, which involves hydrogen bonding between water and the DMSO aggregate species, 2. probe-dependent solvation dynamics directly measures the heterogeneity of solutions, 3. amide additives increase the amount of water within the DMSO first solvation shell.

20181015_화학과 특별세미나_오광임박사.pdf