Microtiter plate assay for superoxide dismutase using MTT reduction by superoxide.

A simple microtiter plate based colorimetric assay for superoxide dismutase is described. The method, involves generation of superoxide by pyrogallol autoxidation and the inhibition of superoxide dependent reduction of the tetrazolium dye MTT [3-(4,5-dimethyl-thiazol-2-yl) 2,5-diphenyl tetrazolium bromide] to its formazan, measured at 570 nm. The reaction was terminated by the addition of dimethyl sulfoxide (DMSO) which also helps to solubilize the formazan formed and the colour evolved was stable for many hours. The method was compared with other known methods to measure the activity of purified erythrocyte Cu,ZnSOD and superoxide dismutase activity from various rat tissues. This procedure involves inexpensive reagents, allows a rapid and sensitive measurement of SOD activity and the microtiter plate assay is suitable for use with large number of samples.

Potentiometric and conductometric studies on some diphenyformazans and their metal chelates

The ACID dissociation constant pKa values of 1-aryl-5 -[o- hydroxybenzene]-3-benzoylformazan derivatives in ethanol- water mixtures have been determined pH-metrically at 25 +/- 0.2 degree. Increase in the concentration of ethanol results in the increase of pK for all formazan derivatives. The formation constant log kMML values of some lanthanide complexes were determined in 70% [v/v] ethanol. The potentiometric and conductometric studies revealed that 1: 1 and 1: 2 [metal: ligand] complexes were formed in solution. The correlation of the stability constants of complexes in relation to ionic radii, ionic potential and electronegativity of the lanthanides was discussed