Forces at biological interfaces: insights from neutron reflectometry

Abstract:  

Neutron reflectometry (NR) is a powerful method to interrogate the structure of multilayered thin films at interfaces and has found application in many areas in both hard and soft condensed matter. A key feature of neutron scattering for structural analysis is its isotope sensitivity, which can often be exploited in biological or biomimetic systems just by changing the aqueous medium from H2O to D2O. In many cases, NR is the most direct structural technique to probe interfacial phenomena in these systems; in this talk, following a general introduction to NR, I will discuss two examples in which NR revealed the strong interfacial forces at the surface of lipid bilayer membranes. In the first, https://pubs.acs.org/doi/full/10.1021/jacs.3c12348, counterintuitively, charged membranes are observed to strongly repel neutral nanoscale particles from its surface, creating a water-rich exclusion zone near the membrane surface. I will show that this effect is related to the formation of extremely strong local field gradients in the electric double layer; these repel neutral particles both by dielectrophoresis and counterion pressure. In the second, https://doi.org/10.1021/acs.langmuir.1c00214, I will demonstrate how substrate-supported lipid bilayers can be decoupled from the substrate by tuning the surface charge of the substrate. Finally, I will discuss several recent developments in NR: the new, highly parallelized CANDOR reflectometer at the NIST Center for Neutron Research, and the role that automation and active learning can play in accelerating data collection and discovery with NR.