Rhodopsin is the mammalian dim-light receptor, and the best characterized member of the G protein-coupled receptor (GPCR) family of membrane proteins. We have worked on multiple aspects of rhodopsin function, including the role of lipid-protein interactions in modulating rhodopsin function, the properties of water inside the protein during activation, and the overall mechanism of rhodopsin activation.![](http://membrane.urmc.rochester.edu/wp-content/uploads/2019/01/rhodopsin.png)
More recently, we’ve been working to model the picosecond-timescale dynamics immediately following photon absorption. This is a collaboration with experimentalists from the University of Arizona (Michael Brown’s lab), Arizona State (Petra Fromme, Rick Kirian, Abhishek Singharoy), and Hauptmann-Woodward (Tom Grant). Using X-ray free-electron lasers, we measure time-resolved small-angle and wide-angle X-ray scattering (SAXS and WAXS) for rhodopsin in detergent micelles. Comparing dark state rhodopsin with activated protein in a pump-probe experiment reveals the perturbations due to photon absorption. We use classical simulations in a similar format to elucidate the atomic-level motions leading to the measured signals.