[Staining with naphthol yellow S. 1. Evaluation of the Keq of the protein-dye binding reaction].

A histochemical technique, using acid dye NY-S, for quantitative determination of proteins was tested using cultured cells fixed in a fixative mixture of methanol, acetic acid, formalin (85:5:10, v/v) and stained with increasing ratios of [Dye-]/[R-HN+3] for times up to 30 min. We attempted to evaluate the Keq of the binding reaction of NY-S to proteins. Using a Microphotometer Leitz M PV 2; we have not found the saturation level. We think that this is due either to the presence of secondary binding sites between dye and proteins and stacking phenomena of the dye, or to factors affecting measurements.