Molecular and Mechanical Manipulation of Membrane Domains in Planar Supported Bilayers

Abstract

Nano-membrane domains are hypothesized to play an integral role in many cell signaling pathways. Their transient nature and biocomplexity underlies a myriad of fundamental questions about lipid-lipid and lipid-protein interactions and their roles in cellular functions. As a result, there is a need for innovative approaches for understanding different biophysical aspects of membrane assemblies and their underlying, multiscale dynamics. Here, we integrate dynamic holographic optical trapping (HOT) and fluorescence imaging with fluorescence correlation spectroscopy (FCS) to characterize membrane domain nucleation in biomimetic planar supported bilayers. The dynamic HOT system allows for the creation of multiple traps from a single light source, each of which can be controlled individually in real time. Silica microspheres are being trapped into arbitrary patterns for system optimization. Receptor-bound microspheres associated with nano-domains in planar supported bilayers act as handles for dynamic HOT manipulation. Our hypothesis is that by trapping multiple microsphere-bound receptors, the associated heterogeneous lipid domains will nucleate a larger domain upon interaction in a manner that depends on the lipid type, cholesterol and protein content. Fluorescence imaging is used to visualize lipid domain formation, and subsequent lateral diffusion of lipid species will be measured with FCS as a function of trap-induced confinement. These results will ultimately lead to new insights into domain formation in membranes.