Observations on the chromatin staining by aluminium-hematoxylin

The staining reaction of chromatin by aluminium-hematoxylin was investigated. Intense staining, which proved dependent on nucleic acid content, was achieved by using either the preformed lake, mordanting followed by hematoxylin, hematoxylin alone or the lake at high ionic strength. Extraction procedures removed aluminium ions from chromatin but the lake was retained. Chromatin fluorescence induced by ethidium bromide and acridine orange was abolished after staining with the lake. Intercalating-like forces are suggested for aluminium-hematoxylin binding to chromatin.