The Berger Lab uses a combination of state-of-the-art genetic engineering and biophysical methods to examine dynamic structural changes in myosin, the motor protein that drives muscle contraction at the molecular level. Both intrinsic (e.g. tryptophan) and extrinsic (e.g. rhodamine) fluorescent probes are incorporated at specific sites in myosin using site-directed mutagenesis, and provide a means by which conformational changes in myosin associated with critical steps in the contractile cycle (i.e. nucleotide binding and hydrolysis, actin binding, and the powerstroke) can be directly monitored with high resolution spectroscopic techniques. Observed structural changes are correlated in real-time with the enzymatic and mechanical functions of myosin using stopped-flow kinetics and single molecule force and motility assays. Together, these techniques allow us to construct a detailed dynamic description of the molecular motions in myosin responsible for generating force and motion during muscle contraction and other types of actin-myosin based motility in cells.