Quantitative aspects of the Naphthol Yellow S staining for proteins studied in a model system of polyacrylamide films and in isolated rat liver cells and nuclei.

After staining with Naphthol Yellow S (NYS) at optimal conditions of pH (2.8), the protein content of rat liver cells isolated by means of a collagenase perfusion technique was found to be cytophotometrically immeasurable, because of too high local dye absorbances. In order to lower the absorption values, techniques to flatten the cells, off-peak measurements and NYS staining at non-optimal pH levels were applied. With polyacrylamide model films incorporated with albumin, the reliability of off-peak measurements and the quantitative aspects of the modified protein staining procedures have been investigated. It was found that NYS is a quantitative protein stain not only at pH 2.8, but also at pH 2.0, 3.5 and 4.0 respectively. Off-peak measurements can also produce quantitative results. In cases of a combined Feulgen-NYS staining, the Feulgen-DNA values were not significantly influenced by any of the NYS staining procedures.