Histochemical demonstration of thiols and disulfides by the fluorescent labeling agent, monobromobimane: an application to the hypothalamo-neurohypophysial system.

The use of the new fluorescent labeling agent monobromobimane for the histological visualization of thiols, and, after reduction, of disulfides, is described. Fluorescent labeling of the disulfide-rich neurosecretory proteins in the hypothalamo-neurohypophysial system of rat and frog is shown. The reaction of the non-fluorescent reagent with thiols results in highly fluorescent materials which resist fading. The labeling procedure is very simple, rapid, and is carried out in one step. It is non-destructive and can allow for biochemical analyses of the labeled tissue.