Studies on the Structure of Bovine Serum High Density Lipoprotein Using Covalently Bound Fluorescent Probes

Abstract Fluorescence polarization, fluorescence lifetime, and sedimentation velocity measurements on fluorescent conjugates of bovine serum high density lipoprotein with 1-dimethylaminonaphthalene-5-sulfonate and 1-pyrenebutyrate provide considerable information on the structure of the lipoprotein, including its rotational diffusion, size, shape, flexibility, and response to substances which alter the structure of biological membranes. Bovine serum high density lipoprotein has an average rotational relaxation time of 570 ns at 25°; it is a relatively rigid, spherical particle with some local flexibility at the level of protein side chains and the individual lipid components. In the presence of increasing amounts of 1-octanol, the lipoprotein first expands and finally becomes disrupted. The structural changes are qualitatively similar to those produced by alcohol anesthetics on biological membranes.