Quantitative Model of the Enhancement of Peroxidase-Induced Luminol Luminescence

Abstract

Many phenolic compounds are known to enhance the chemiluminescence associated with the horseradish peroxidase-catalyzed oxidation of luminol, but the mechanism of enhancement is still unproved. Using stoppedflow spectrophotometry, we have found that a series of luminescence enhancers react rapidly with the peroxidase reactive intermediates (compound I and compound II) supporting the hypothesis that the enhancement is due to the acceleration of the enzyme turnover. In addition, pulse radiolysis experiments have shown that the enhancers' phenoxyl radicals oxidize luminol, consistent with a redox mediator role for the enhancers. The latter reaction was found to be reversible, showing that enhancers of low reduction potential, which are efficient in accelerating the enzyme turnover, are also scavengers of luminol radicals and therefore luminescence quenchers. Using these data, a simple model is proposed which correctly predicts that the efficiency of a phenolic compound as luminescence enhancer depends on the reduction potential of the respective phenoxyl radical according to a bell-shaped function with a maximum at ∼0.8 V.

Comparison Between Acridan Ester, Luminol, and Ruthenium Chelate Electrochemiluminescence

“…In particular the possibility that the azasemiquinone can undergo disproportionation (Scheme 2c) [46,47] or further electrochemical oxidation (Scheme 2b) [48] were overlooked. Both pathways lead to the formation of luminol azaquinone, which is known to react chemiluminescently with hydrogen peroxide [49].…”

Photodynamic action of some sensitizers by photooxidation of luminol

“…Miyazawa and colleagues proposed that the interaction of singlet oxygen with LUM molecules results in the formation of an endoperoxide (Miyazawa et al 1994). Decomposition of the transient endoperoxide yields the end products APA and nitrogen (N 2 ) and light emission (Easton et al 1996). Energy transfer from an excited photosensitizer to ground state molecular oxygen generates singlet oxygen which then oxidizes LUM to APA; a reaction which describes a Type II oxygen-dependent mechanism.…”

Determination of Nicotinamide in Food and Human Fluid Samples by Capillary

“…Nicotinamide contains an amido group, making it easily oxidized especially in alkaline solution. Therefore, the potential inhibitory mechanism of nicotinamide on the CL reaction on luminol and K 3 Fe(CN) 6 could be that the consumption of K 3 Fe(CN) 6 , which is the oxidant of luminol-K 3 Fe(CN) 6 system, led to a decrease in CL intensity 20,21 or nicotinamide acted as scavengers of luminol radicals like phenolic species of low reduction potential, 22,23 and then quenched the CL intensity.…”