A fluorescence microscope coupled to a photon counting spectrofluorometer will be used to obtain fluorescence spectra, fluorescence-detected dichroism and fluorescence polarization data on labeled tropomyosin, actin and troponin incorporated into oriented muscle myofibrils and fibers. Prior work on fibers has indicated that actin subunits slightly reorient when myosin heads bind to ghost fibers not containing the regulatory proteins and when calcium binds to the regulatory proteins on the thin filament in the absence of myosin. No studies appear to have been reported of possible reorientation of actin subunits associated with myosin head binding to actin containing the regulatory proteins. This project will provide new information about subunit reorientation assoicated with regulation in systems that are close to in vivo muscle and will help to clarify the mechanism of the regulation of muscle contraction.***//
