This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Bicelles provide an environment wherein proteins can interact with a bilayer structure composed of biologically competent lipids, packaged into a particle size that is sufficiently small to allow for rapid tumbling times in solution for NMR and for high protein concentrations and uniform distributions in the frozen samples used in pulsed dipolar ESR spectroscopy. According to this, it was necessary to engineer suitable bicelles and explore their utility for studies of protein-membrane interactions. We pursued the following specific goal: (1) to prepare bicelles as biological membrane mimetics, based on different compositions and ratios of long chain to short chain lipids; (2) to characterize their size and stability with respect to their loading with protein.