  We report a theoretical/computational approach for modeling the
current-voltage characteristics of sensing proteins. The modeling is applied to
a couple of transmembrane proteins, bacteriorhodopsin and proteorhodopsin,
sensitive to visible light and promising biomaterials for the development of a
new generation of photo-transducers. The agreement between theory and
experiments sheds new light on the microscopic interpretation of charge
transfer in proteins and biological materials in general.
