Structure and Dynamics of Crystalline Protein Layers Bound to Supported Lipid Bilayers

Abstract

We study proteins at the surface of bilayer membranes using streptavidin and avidin bound to biotinylated lipids in a supported lipid bilayer (SLB) at the solid-liquid interface. Using X-ray reflectivity and simultaneous fluorescence microscopy, we characterize the structure and fluidity of protein layers with varied relative surface coverages of crystalline and noncrystalline protein. With continuous bleaching, we measure a 10-15% decrease in the fluidity of the SLB after the full protein layer is formed. We propose that this reduction in lipid mobility is due to a small fraction (0.04) of immobilized lipids bound to the protein layer that create obstacles to membrane diffusion. Our X-ray reflectivity data show a 40 A thick layer of protein, and we resolve an 8 A layer separating the protein layer from the bilayer. We suggest that the separation provided by this water layer allows the underlying lipid bilayer to retain its fluidity and stability.

Controlled solvent-exchange deposition of phospholipid membranes onto solid surfaces

“…The continuous bleaching method 24,35,36 was used to characterize the dynamics of the generated membranes. According to the theory of the method, the spatial intensity of a fluorescently labeled membrane is described by simultaneous photobleaching and replenishment of fluorescent molecules as they diffuse in two dimensions.…”

Neural Networks Grown on Organic Semiconductors

“…The distance between the cell membrane and the surface of a silicon dioxide substrate is in the order of tens of nanometers. [8,9] Moreover, when the organic material is coated with a lipid membrane, this membrane acts as bi-functional, [10] ultra-thin dielectric layer (floating top gate) separating the biological system from the charge transport layer. [11] On this rationale, we investigated the possibility to seed, adhere, and grow both primary neurons and one-cell derived neural stem cells on the most widely investigated organic semiconductor pentacene.…”

Phase separation of phospholipid multilayers incorporated with cell penetrating peptides

“…30, the electron density of a protein is lower than that of the lipid headgroup, but higher than that of the hydrocarbon chain; therefore, after the incorporation of the TDP, the increased averaged electron density of the lipid tail layers indicates that the electron density of TDP molecules is somewhat added into that of the hydrocarbon tails. The results can be explained only if the peptides adsorbed at the surface transform to a form perpendicular to the plane of the membrane.…”