Hydrogen Bond Networks Near Supported Lipid Bilayers from Vibrational Sum Frequency Generation Experiments and Atomistic Simulations

TL;DR

This study combines vibrational sum frequency generation experiments and atomistic simulations to analyze hydrogen bonding networks near supported lipid bilayers, revealing salt effects and specific water-lipid interactions.

Contribution

It provides new insights into interfacial water interactions and the influence of salt on lipid bilayer surfaces using combined experimental and simulation approaches.

Findings

Salt has negligible impact on OH stretching spectra in simulations.

SFG intensity changes are due to chi(3) and potential contributions.

Specific hydrogen bonds between water and lipid head groups identified.

Abstract

We report vibrational sum frequency generation spectra from supported lipid bilayers in which the OH and the CH stretching signals are probed at different salt concentrations. Atomistic simulations show a negligible impact of salt on the OH stretching spectra, indicating the observed SFG intensity changes are due to chi(3) and potential dependent contributions. These are further analyzed in the contact of exact-zero reference states. Further experiments and simulations identify specific hydrogen bonding interactions between interfacial water molecules at the PC head group of the zwitterionic DMPC lipids at 3200 wavenumbers.