Primary and Secondary Hydration Forces between Interdigitated Membranes Composed of Bolaform Microbial Glucolipids

TL;DR

This study investigates the primary and secondary hydration forces between interdigitated microbial bolaform glycolipid membranes using osmotic stress and neutron diffraction, revealing distinct ionic strength sensitivities and decay lengths.

Contribution

It provides new insights into hydration forces in non-membrane glycolipid systems, specifically microbial bolaform glycolipids, using combined osmotic stress and neutron diffraction techniques.

Findings

Identified primary and secondary hydration regimes with different ionic strength sensitivities.

Measured decay lengths of hydration forces: 0.37 nm and 1.97 nm.

Demonstrated that hydration forces depend on ionic conditions.

Abstract

To better understand lipid membranes in living organisms, the study of intermolecular forces using the osmotic pressure technique applied to model lipid membranes has constituted the ground knowledge in the field of biophysics since four decades. However, the study of intermolecular forces in lipid systems other than phospholipids, like glycolipids, has gained a certain interest only recently. Even in this case, the work generally focuses on the study of membrane glycolipids, but little is known on new forms of non-membrane functional compounds, like microbial bolaform glycolipids. This works explores, through the osmotic stress method involving an adiabatic humidity chamber coupled to neutron diffraction, the short-range (< 2 nm) intermolecular forces of membranes entirely composed of interdigitated glucolipids. Experiments are performed at pH 6, when the glucolipid is partially negatively charged and for which we explore the effect of low (16 mM) and high (100 mM) ionic strength. We find that this system is characterized by primary and secondary hydration regimes, respectively insensitive and sensitive to ionic strength and with typical decay lengths of 0.37 +- 0.12 nm and 1.97 +- 0.78 nm.