Reactions of Dyes with Cell Substances

Thionine is a metachromatic stain commonly used by histologists. In our preliminary survey of the staining of smears of purified nuclear materials (l), it was noted that thionine gave color variation but not reliable differentiation among the substances. The color variations were not conditioned by pH or by the acidity or basicity of the materials, as with hematoxylin. Thionine has been much used in tissue sections to distinguish empirically between mucin or mucoid (staining violet) and nuclei (blue), and important physiological theories depend on this. We felt that if this metachromatic differentiation could be studied with the purified proteins, the histological test might be validated and information might be gained concerning the mechanism of the differential staining. The proteins used in our experiments were beef salivary mucin or osseomucoid, and nucleohistone or cr-nucleoprotein. Nucleic acid was also used in some cases. The thionine was the commercial product as provided for histological staining; for most of the experiments this was recrystallized from hot water and alcohol. Thionine is one of a large group of basic dyes which, as Holmes (2) showed, exist in one colored form in concentrated and another