Bacteriorhodopsin Analogue from Indolic Chromophores

A new analogue of bacteriorhodopsin (bR) was prepared by allowing bacterioopsin (bOP), the apo-protein of bR to interact with (2Z,4E)-3-chloro-5-(1H-indol-3-yl)-2,4-pentadienal as chromophore. It was characterised for its opsin shift, stability, light-induced pH change and fluorescence emission. Indolic aldehydes viz. 1H-indole-3-carboxaldehyde and (2Z,4E)-3-chloro-5-[1-(phenylsulfonyl)-1H-indol-3-yl]-2,4-pentadienal did not bind bOP.