After bacteriorhodopsin, halorhodopsin may be the best type I (microbial) opsin studied. Peak absorbance of the halorhodopsin retinal complex is about 570 nm.
Bacteriorhodopsin and halorhodopsin are both types of microbial opsins, with bacteriorhodopsin being a well-studied example. The peak absorbance wavelength for the halorhodopsin retinal complex is approximately 570 nm.