In collaboration with the Yan group at Yale, and the Birge group at UCONN, we are using ssNMR to study the basis for modulation of the retinal photophysics of retinal in either rhodopsin or bacteriorhodopsin by site specific mutations. The Yan group has prepared several mutants of rhodopsin and other visual pigments where the optical properties or lifetimes of photo-intermediates are affected my particular point mutations. C-13 NMR is being used to correlate these effects with changes in retinal conformation or disruption of hydrogen bond networks. At UCONN the Birge group has evolved several bR mutants with exceptionally attractive properties with respect to use in optical memories. We are trying to again elucidate by C-13 NMR the structural consequences on retinal conformation in the various optical states.