The effect of ligand subs titutions on catalytic activity of Heme – Imidazo le deriv atives – SDS complex as a nano artificial enzymes

Artificial enzymes are manufactured from s ynthetic m aterials by simulation of natural enzyme functions. Heme gr oup has the functional role in many hemopr oteins like peroxidases. The microenv iroment of heme and also it’s ligands are very significant in cat alytic activity of hemoproteins. Because of Heme tendency to dimerization in aqueous solutions, It’s own catalytic activity is decreased in aqueous media. In critical concen tration of d etergents like SDS, the strong hydropho bic interactions between detergent and porphyrine group ca n overcome the porphyrine – porphyri ne forces a nd porphyrine can be solubilized. In hemoproteins proximal hetero cyclic nitrogen ligands like histidine can catalyze t he oxidation of variety o f substrates via reacting with hydrogen peroxide. In biomimetic chemistry, simulation of histidine is done by imidazole containing ligands. A surfactant – imidaz ole derivati ve – heme is known as nano art ificial enzyme. Herein two sulfonyl imidazole a nalogues (۱- (benzensulfonyl)-۱H-im idazole, ۱-tosyl- ۱H-imida zole) were compared in terms of activation o f heme – SDS comple x as a perox idase like nano artificial enzyme. The catalytic ac tivity of the designed models was evaluated b y the oxidation reaction of guaiacol with H۲O۲ at ۴ ۷۰ nm (λma x for the product of the c atalytic rea ction)using a model Shi madzu-۳۱۰۰ spectrophotometer. O btained kin etic parameters showed that catalytic efficiency of Tosyl i midazole is about ۲.۲ times of B enzen imid azole’s catalytic efficiency. It is kno wn that heterolytic cleavage of O–O bond of H۲O۲ is the key step of peroxidase mechanism that leads to generation of compound I. Tosyl group provide a favored stereoelectronic environment for the active site of heme-peroxidase which promotes the heterolytic cleavage of O-O BONDin hydrogen peroxide.