The chemistry of the DNA-p-Nitrophenylhydrazine reaction

The chemistry of the reaction between DNA and pNPH has been investigated by isolation and analysis of the chromogen. The perchlorate of the cationic chromo-gen was prepared from the reineckate by anion exchange chromatography, and samples from both DNA-pNPH and furfuryl alcohol-pNPH reaction mixtures were found to have identical i.r. and p.m.r. spectra. The data obtained from the p.m.r. spectra were consistent with a reaction scheme involving formation of a pyridazinium cation which subsequently yields the chromophore on treatment with alkali.