Iodonitrotetrazolium

Iodonitrotetraolium is an artificial electron acceptor which can be utilized in a colorimetric assay to determine the concentration of protein in a solution. It can be reduced by succinate dyhydrogenase to Forazan, the formation of which can be measured by absorbance at 490nm. The activity of succinate dehydrogenase is readily observed by the naked eye as the solution turns from colourless to rusty red.