title: The staining properties of pyridylazophenol analogs in histochemical staining of a metal.
abstract: The compound 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP) was found capable of staining very small amounts of metals in tissue. This finding stemmed from the examination of the staining properties of pyridylazophenol analogs; 2-(2-pyridylazo)-phenol, 2-(2-pyridylazo)-5-dimethylaminophenol, 1-(2-pyridylazo)-2-naphthol, 4-(2-pyridylazo)-resorcinol, and Br-PADAP. The unusually high sensitivity of Br-PADAP is attributed to the presence of an alkylamino group at the 5-position of the benzene ring. The presence of this alkylamino group forms a charged quinoid structure, and contributes resonance and optimum solubility to the hybrid by introducing a bromine atom into the pyridine ring. We report the staining results obtained from a variety of metals and the molar absorptivity of their metal chelates.
mesh_terms: D000818:Animals; D001391:Azo Compounds; D006651:Histocytochemistry; D008099:Liver / Q000166:cytology; D008670:Metals / Q000032:analysis*; D051381:Rats; D013194:Staining and Labeling
chemical_list: D001391:Azo Compounds; D008670:Metals; C037882:2-(5-bromo-2-pyridylazo)-5-diethylaminophenol