Noncovalent interactions with proteins modify the physicochemical properties of a molecular switch

It is reported that spiropyran— aw idely investigated molecular photoswitch—can be stabilized in aqueous environments in the presence of av ariety of proteins, including human serum albumin, insuli nf ibrils, lysozyme, and glucos eo xidase. The optical properties of the complexed photoswitch are protein dependent, with huma ns erum albumin providing the spiropyran with emission features previously observed for ap hotoswitch confined in media of high viscosity .D espite being bound to the protein molecules ,s piropyra nc an undergo ar ing-opening reactio nu pon exposure to UV light. This photoisomerization process can affect the properties of the proteins :h ere, it is shown that the electrical conduction through huma ns erum albumin to which the spiropyran is bound increases following the ring-opening reaction. Bacteriorhodopsi nh as long impressed scientists with the elegance with whic hi tu ses the energy of sunlight to guide the motion of protons across cell membranes. This functio ni se nabled by ap hotoswitchabl er etinal moiety strategically positioned within the protein structure ;l ight-induced isomerization of retinal trigger sa cascade of reactions, resulting in proton transfer against ap Hg radient. [1, 2] Inspired by this and other examples, [3] chemists have developed different strategies to covalently immobilize photoswitchabl em olecules within various biomacromolecules, [4–9] with the primary goal of controlling their structures and/or functions. Attractive and diverse applications have become possible, including photoswitchable enzymati cc atalysis [10, 11] and light-actuated ion transport through