[Staining with naphthol yellow S. 2. Study of the reversibility of the protein-dye binding reaction].

In the present work we studied the reversibility of the binding reaction of Naphthol Yellow S to proteins using a Testing Automatic System Leitz. We presently think that the NY-S staining procedure, can be used as a reliable quantitative method for the determination of nuclear and cytoplasmic proteins only under standardized conditions: the ratio R = [Dye-] / [R-NH+3] must be more greater than 10; for staining periods shorter than 45 min, the slides, at equilibrium, must be mounted in dyeing solution; for quantitative determinations using irreversible bound dye, the staining period must be significantly longer than 45 min (see above) and differentiated in running water for several hours.