Structural Optimization of Photoswitch Ligands for Surface Attachment of alpha-Chymotrypsin and Regulation of Its Surface Binding

A modified gold surface that allows photoregulated binding of alpha-chymotrypsin has previously been reported. Here the development of this surface is reported, through the synthesis of a series of trifluoromethyl ketones and alpha-keto esters containing the azobenzene group and a surface attachment group as photoswitch inhibitors of alpha-chymotrypsin. All of the compounds are inhibitors of the enzyme, with activity that can be modulated by photoisomerization. The best photoswitch shows a reversible change in IC50 inhibition constant of >5.3 times on photoisomerization. The trifluoro-methyl ketone 1 exhibited excellent photoswitching and was attached to a gold surface in a two-step procedure involving an azide alkyne cycloaddition. The resulting modified surface bound a-chymotrypsin to a degree that could be modulated by UV/Vis irradiation. showing slow-tight enzyme binding as observed for inhibitors in solution.