This award supports cooperative research in biophysics to be conducted by Giuseppe Inesi of the University of Maryland at Baltimore and Leopoldo de Meis of the Federal University in Rio de Janeiro, Brazil. The topic is calcium transport across biological membranes. The specific aim is to clarify the mechanisms of calcium uptake in membrane vesicles obtained from muscle tissue. The biological significance of the research is related to the contraction and relaxation of muscle fibers. Chemical significance lies in understanding enzyme kinetics and catalysis, the coupling of catalytic and tranport activities, channels and transmembrane flow of electrolytes and the structure of proteins. There has been a long-standing, productive collaboration between Dr. Inesi and several Brazilian scientists who, as postdoctoral associates, have spent extended periods of time in his laboratory. This grant will allow for the continuation of this cooperation and enhance Dr. Inesi's participation in the work in Brazil. Both investigators are well qualified and will carry out work on an important problem in a vital area of research.