Catalytic spectrophotometric techniques

Finally, and in the framework of this kind of methods, the use of catalytic spectrophotometric techniques (CST) must be considered. In this sense, the ability of traces of the... 

While the main advantage of catalytic spectrophotometric methods is low cost of the needed equipment, chromatography is arguably the most widely used separation technique in the... 

We recognized the need for methodology to measure SOD activity directly that would be more accessible to the bench-top scientist than is the method of pulse radiolysis, another direct measure. Consequently, we developed methodology to measure the catalytic dismutation of superoxide by stopped-flow kinetic analysis.By this technique, we directly monitor the decay of superoxide spectrophotometrically in the presence or absence of a putative SOD mimic at a given pH. Kinetic analysis of this decay can determine whether the complex is a SOD mimic (decay of superoxide becomes first-order in superoxide and first-order in complex see equations 1 and 2), or is inactive (decay of superoxide remains second-order for its self-dismutation see equation 3). At least a tenfold excess of superoxide over the putative SOD mimic is used in the stopped-flow assay, to eliminate contributions due to a stoichiometric reaction of the complex with superoxide. A catalytic rate constant for the dismutation of superoxide by the complex can be determined from the observed rate constants of superoxide decay as a function of catalyst concentration. ... 

Today, spectrophotometric methods are almost solely used for determination of the catalytic activities of enzymes in physiological samples in both manual and automated techniques because of their ease, simplicity, and sensitivity. No sampling is required, no reagents are necessary other than the actual reactants, and the result can be obtained with one small sample. 

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