N. Kampf, Y. Dong, Y. Schilt, W. Cao, U. Raviv, J. Klein
Weizmann Institute of Science,
Keywords: lipid bilayers, hydration, mechanical properties, friction
Summary:The robustness of lipid phosphatidylcholine (PC) lipid bilayers at the joint articular cartilage and other biological surfaces is very much effecting its functional properties such as pressure resistance and friction. In our previous studies(i.e. 1-2), we demonstrate the efficiency of PC lipids in reducing surface friction, with the understanding that highly hydrated PC head-groups are important for the low friction as well as for the normal joint function. To check this hypothesis we probed the dehydration (by DMSO addition) of PC-lipid bilayers by nanotribological (surface force balance) and nanomechanical (SPM) measurements. Unexpectedly, we found that the dehydration has little effect on the friction with an increase of bilayer modulus. In my talk, I will explain this puzzling discrepancy by several approaches, including small- and wide-angle X-ray scattering and all-atom molecular dynamics simulations. Our findings(3) sheds strong light on the robustness of lipid-based hydration lubrication in biological systems, despite the ubiquitous presence of bio-osmolytes which compete for hydration water. (1) Soft Matter, 2016, 12, 10, 2773-2784. (2) Langmuir, 2019, 35, 48, 15459-15468. (3) Nanoscale, 2022, 14, 18241-18252. Weizmann Institute of Science, Israel, (b) Institute of Chemistry, The Hebrew University of Jerusalem, Israel, (c) Department of Physical Chemistry, School of Chemistry, Tel Aviv University, Israel.