[The cytospectrophotometrical determination of proteins by the tetrazonium coupling reaction. I. Optimization of the staining method (author's transl)].

The tetrazonium coupling reaction using Fast blue salt B and the sodium salt of 6-hydroxy-naphthalinsulfonic acid-(2) serves as a method for histochemical demonstration of proteins. Fast blue salt B reacts with histidin, tyrosin and in a slighter extent also with tryptophan. It is shown in this paper, that the histochemical tetrazonium reaction carried out under the optimal conditions is a specific staining for proteins and highly reproducible. The maximum of absorption at lambda = 530 nm of the azo dyes generated by the coupling reaction followes the Lambert-Beer's law. Nucleic acids as well as protein-SH-groups do not react with Fast blue salt B under the conditions described. Due to the exact reproducibility and specifity the tetrazonium coupling reactions seems to be a suitable method for at least comparative, microspectrometric protein determination within one species of cells.