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 IC(50) inhibition constant of >5.3 times on photoisomerization. The trifluoromethyl 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 alpha-chymotrypsin to a degree that could be modulated by UV/Vis irradiation, showing "slow-tight" enzyme binding as observed for inhibitors in solution.