Electrochemical and spectroelectrochemical studies of electrocatalytic reduction of bisulfite
Abstract
Nir and SiR are relatively large heme protein molecules (MW 40,313 and 66,279 Dalton, respectively) and the direct electrical contact of the redox-active heme-sites of hemoproteins and electrodes is usually difficult due to their electrical insulation by the protein matrix. Myoglobin (Mb) is a small hemoprotein (MW is about 17,000 Dalton). It contains a single iron heme as the prothetic group and this heme is the electroactive site of the protein. As active sites of these enzymes (NiR and SiR) and myoglobin are similar, investigating the electrocatalytic behavior of this hemoprotein, myoglobin, with bisulfite will help us to obtain some understanding of the reduction mechanism of HSO3- . Nitrite reduction has been catalyzed by a myoglobin-didodecyldimethyl ammonium bromide (Mb/DDAB) modified glassy carbon electrode (GCE). The similarity between nitrite and bisulfite suggested the possible catalytic reduction of bisulfite using myoglobin on a Mb/DDAB modified glassy carbon electrode. Electrochemical work involved the use of Mb/DDAB modified GCE to study the electrocatalytic reduction of bisulfite. The catalytic reduction of bisulfite seemed to occur at the Fe(II)/Fe(I) redox couple. Bisulfite concentration and scan rate effects were explored. A typical enzyme catalytic behavior was found and the catalytic current increased as concentration of bisulfite was increased. Also, controlled-potential electrolyses of bisulfite using the same electrode and detection of reduction products were performed in different buffer solutions. Spectroelectrochemical measurements on Mb/DDAB films loaded on gold coated optically transparent thin layer glass slide electrode (OTTLE) was carried out. UV-visible spectroscopy was used to investigate the behavior of Mb/DDAB films in the catalytic reduction of bisulfite. Spectral changes including the characteristic bands of the Mb/DDAB films in absence of bisulfite were explored. (Abstract shortened by UMI.)
This paper has been withdrawn.