抄録
1. The precipitability of partially hydrolyzed DNA with histone depends upon the extent of hydrolysis and the histone/DNA ratio. Addition of histone in excess to hydrolyzed DNA causes no precipitation.
2. Presence of excess histone in the reaction mixture consistently gives rise to a shift towards the longer wavelengths of the maximal spectral absorption of the Feulgen pigment under conditions optimal or suboptimal to the color development.
3. The color intensity of the Feulgen reaction is strongly modified by the presence of histone in the reaction mixture. Under the con-ditions favorable to the color development with hydrolyzed DNA alone, histone depresses, and under those unfavorable, it enhances the color intensity, but the intensity is never levelled off. The magnitude of this effect is dependent on the histone/DNA ratio: the higher the ratio, the stronger the effect. Thus the presence of excess histone causes the deviation from the Beer-Lambert law of the Feulgen color.
4. The histone effect is effaced almost completely by concentrated NaCl, suggesting that it is due to the electrostatic combination between hydrolyzed DNA and histone.
5. The bearing of these findings on the problem of the quanti-tative nature of histochemical Feulgen reaction was discussed.
