(121i) Mobility of Strongly Adsorbed Biopolymers on Supported Lipid Bilayers

Diffusion of integral cell membrane proteins in the lipid bilayer is critical for a variety of cellular functions and has been a subject of interest for many years. Extensive theoretical and experimental ideas have been developed to understand the transport properties in such systems. However, of late, there has been a rising interest in understanding the transport properties of non-compact macromolecules strongly adsorbed ?on? and not incorporated into lipid bilayers in light of the relevance for designing improved DNA separation strategies, multivalent cellular effectors, and for gene therapy. Previously, researchers like Radler et al. have suggested that such strongly adsorbed polymers can be treated similar to a polymer in a two-dimensional fluid, but there exists no experimental proof to date. In order to test this hypothesis and also to gain a better understanding of polymer dynamics in two dimensions, we designed an experimental protocol: i.e., lateral transport of a short, single stranded DNA oligonucleotide adsorbed on a supported cationic lipid bilayer. Fluorescence Recovery After Photobleaching (FRAP) analysis reveals that diffusivity of the adsorbed DNA quantitatively tracks that of the underlying lipid, even though the bilayer mobility changes by two orders of magnitude with changes in temperature. Similar experiments are also being carried out for proteins that are strongly adsorbed on supported lipid bilayers. These results for strongly adsorbed biopolymers on a supported lipid bilayer (short, non-compact DNA and globular proteins) will be compared with those reported for globular proteins incorporated into the lipid bilayer and finally, the influence of lipid mobility in the dynamics of such small biopolymer adsorbates will be discussed.