Redox modification of proteins using sequential-parallel electrochemistry in microtiter plates

Redox modification of proteins has frequently been used to improve the elec tron-transfer properties in amperometric biosensors. One approach is the co ordinative labelling of histidine residues with metal complexes like [Ru( b py)(2)Cl-2] and [Ru(bpy)(2)CO3]. Although the reaction depends on a variety of parameters no detailed optimisation of these modification procedures ha s been done, most probably due to the complexity of the parameter matrix an d the expected differences for any individual protein. A multi electrode se quential analyser (MESA) system has been developed which allows one to foll ow in a sequential-parallel scheme a number of modification reactions by pe rforming electrochemical measurements such as cyclic voltammetry or differe ntial pulse voltammetry in individual wells of a conventional microtiter pl ate. Using this system, the ligand exchange reaction leading to the binding of the Ru-complex to histidine residues could be investigated with imidazo le as a model compound. Furthermore, the selective labelling of soluble PQQ (pyrrolochinolinquinone)-dependent glucose dehydrogenase (sGDH) and glucos e oxidase (GOx) with Ru complexes could be optimised and the electrochemica l and biological properties of the obtained 'electroenzymes' were examined.