The D96N mutant form of bacteriorhodopsin (BR) purple membrane fragments isolated from the bacterium Halobacterium salinarium has been immobilized by entrapment in sol-gel glass. The protein was characterized for M state decay rate at different temperatures and pH values. Bleaching efficiency and absorbance maxima vs pH were also determined. The kinetic effects of triethanolamine and diethanolamine were also examined. Results indicated that the immobilized BR was affected in a manner similar to the mutant BR in aqueous suspension. Addition of guanidine, however, caused the immobilized BR to show kinetic parameters more closely related to the wild-type protein than the D96N mutant control. Samples of the aqueous suspension were characterized for particle size and particle size distribution. Dried samples of the immobilized BR were analyzed by field emission microscopy and BET to characterize both the purple membrane fragments and the sol-gel pore characteristics.