Abstract
A horseradish peroxidase (HRP)-catalyzed luminol chemiluminescence (CL) reaction was applied to the detection of hydrogen peroxide (H2O2) formed during the Cu(II)-catalyzed oxidation of amino thiol with oxygen. Cysteamine, L-cysteine, L-cysteine methyl ester and L-cysteine ethyl ester were used as amino thiols. A CL flash suddenly appeared after a certain dark period from the start of the reaction in all thiols used. The appearance of the delayed CL could be explained in terms of quenching function of the thiol for luminol radical formed through the enzymatic cycle of HRP. The quenching rate of luminol radicals with the cysteine esters was remarkably higher than those with cysteamine and cysteine.
