The long-term goals of our research are to understand how protein conformational ensembles are reshaped by perturbations, such as mutation and ligand binding, and to quantify how these perturbations impact protein function and organismal fitness. To accomplish these goals, we create new computational and biophysical approaches to study how proteins move between different conformational states. As a graduate student, with Tom Alber at UC Berkeley, James established room temperature X-ray data collection techniques and electron density sampling strategies to define protein conformational ensembles essential for catalysis. Prior to starting an independent position at UCSF, he was a visiting EMBO Short Term Fellow in the lab of Dan Tawfik at the Weizmann Institute of Science in Israel and developed expertise in directed evolution and high-throughput assays of enzymatic or binding activity. In 2011, James started his independent research career as a QB3 at UCSF Fellow and in 2013 was appointed as an Assistant Professor of Bioengineering and Therapeutic Sciences. At UCSF, his lab continue to pioneer new methods for extracting the maximal information from X-ray diffraction experiments and electron density maps. Additionally, the group uses two complementary approaches to study the relationship between protein conformational ensembles and function. To dissect consequences of mutations on organismal fitness, we use high-throughput systems biology and biophysical methods to analyze large sets of clinically or biophysically interesting mutations. To improve our ability to engineer new protein functions, we investigate changes to the conformational ensemble as new enzymatic and binding functions emerge from directed evolution studies.