Browsing by Author "Rubin, Shai"

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Open Access
Photoregulation of α-chymotrypsin activity in organic media : effects of bioimprinting
(1994) Willner, Itamar; Lion-Dagan, Mazzi; Rubin, Shai; Wonner, Johann; Effenberger, Franz; Bäuerle, Peter
α-Chymotrypsin exhibits photoswitchable activities in an organic solvent after covalent modification of the protein backbone with thiophenefulgide active ester (2). The thiophenefulgide-modified α-chymotrypsin exhibits reversible photoisomerizable properties between states (3)-E and (3)-C. The modified α-chymotrypsin, where nine lysine residues are substituted by thiophenefulgide units, retains 60% of the activity of the native enzyme. The activities of thiophenefulgide-modified α-chymotrypsin toward esterification of N-acetyl-L-phenylalanine (4) by ethanol in cyclohexane are controlled by the configuration of the attached photoisomerizable component and by prior bioimprinting of the protein backbone with the reaction substrate (4). The esterification of (4) in cyclohexane using bioimprinted (3)-C is two-fold faster than in the presence of (3)-E. In the presence of a nonbioimprinted enzyme, esterification of (4) by (3)-C is five-fold faster than with (3)-E. The activity of bioimprinted (3)-E toward esterification of (4) is 4.5-fold higher than that of nonbioimprinted (3)-E. Switchable cyclic esterification of (4) is accomplished by sequential photoisomerization of the thiophenefulgide-modified α-chymotrypsin between states (3)-C and (3)-E.
Open Access
Photoswitchable binding of substrates to proteins : photoregulated binding of α-D-mannopyranose to concanavalin A modified by a thiophenefulgide dye
(1992) Willner, Itamar; Rubin, Shai; Wonner, Johann; Effenberger, Franz; Bäuerle, Peter
Macromolecules exhibiting photoswitchable physical or chemical properties are extensively examined as information storage and signal amplification materials. Photoregulated "on-of" biomaterials provide a novel means to design targeted therapeutic agents activated and deactivated by external light signals. Various means to photoregulate biotransformations by light-switchable enzymes have been described and include the modification of the enzyme active site and protein backbone by photochromic components and immobilization of enzymes in photochromic copolymers. Here we wish to report on the photoregulation of the binding properties of a protein by its chemical modification with photochromic units. We describe the photoswitchable binding of saccharides to concanavalin A modified by thiophenefulgide dye.