Spectral Tuning:
There are four visual pigments in the human retina: rhodopsin, the pigment of rod photoreceptor cells, and the blue, green and red color vision pigments of cone photoreceptor cells. These four pigments have absorption spectra which span (actually define) the visible region of the electromagnetic spectrum. And yet, the small molecule chromophore responsible for absorption of light is the same in each pigment. One of the goals of our research is to understand the underlying mechanism by which the spectrum of each pigment is “tuned” by interactions of the retinal chromophore with amino acid side chains in the active site of the proteins.