Bilayers formed by dispersing lipids in water are models for biological membranes and for assemblies of components with internal conformational freedom. The primary focus of our work is on how bilayer properties like phase behavior, dynamics, and bilayer organization, are affected by factors like protein-lipid interaction, lipid unsaturation, membrane surface charge, and hydrostatic pressure. With deuterated components incorporated into bilayers, wideline deuterium NMR observations reflect the extent to which the orientation-dependent quadrupole interaction is modulated by molecular motions. The bilayer state can then be characterized by the amplitudes and timescales for motions ranging from reorientation of molecular segments to bilayer collective motions.

Structural reorganization of bilayer material is biologically important and relevant to material applications. A surfactant layer that aids breathing by reducing surface tension at the lung air-water interface arises from structural reorganization of multilamellar bilayer material. We collaborate with colleagues in Biochemistry to study how protein-lipid interactions drive such transformations. This is relevant to the treatment of respiratory disease and also suggests strategies for control of bilayer organization in material applications like drug encapsulation.

The motions of membrane proteins affect functions like transmembrane signaling. Polypeptides modeled on protein segments can be studied by attaching deuterium atoms and observing by NMR. We use specially designed polypeptides to study how specific structural features can promote peptide association and, in turn, how such associations affect bilayer properties. Segments of lung surfactant proteins are also observed in this way to determine how surfactant layer maintenance depends on interactions between proteins.

We are one of only a few groups able to observe membranes under pressure using wideline NMR. By using pressure to perturb bilayers, we study how interactions between bilayer components mutually determine their conformations in the bilayer and observe phases that are not seen at ambient pressure. This teaches us about bilayer material properties and helps us understand how marine organisms accommodate changes in pressure.

Our primary tools are two wideline NMR spectrometers built by M. Morrow and students. One based on a 3.5 T widebore superconducting magnet is used primarily for variable pressure studies of samples containing deuterium-labeled lipids.