Merocyanines as Extremely Bathochromically Absorbing Chromophores in the Halobacterial Membrane Protein Bacteriorhodopsin

Extremely bathochromically absorbing derivatives of the halobacterial membrane protein bacteriorhodopsin(λmax = 570 nm) form upon incorporation of merocyanine dyes of the type shown below into the protein binding site. Upon covalent attachment to the protein (through formation of a protonated Schiff base), these compounds convert in to hemicyanines in which the positive charge is distributed over the entire π system of the chromophore.