This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Many of the proteolytic reactions of blood coagulation are catalyzed by membrane-bound macromolecular enzyme complexes composed of a serine proteinase associated with a cofactor protein. We have developed a series of fluorescent derivatives that allow FRET measurements of the cofactor-proteinase and substrate-enzyme complex interactions. Our goal is to extend these studies to permit lifetime imaging on enzyme complex assembly and substrate delivery on blood cells and eventually in the vasculature in the living mouse. We would like to do a series of experiments to assess the feasibility of such approaches using supported membrane bilayers and/or cultured adherent cells.