Influence of acid concentration and temperature on fixed chromatin during feulgen hydrolysis

Summary Labelled nucleic acid were extracted from fixed, air-dried smears of Ehrlich's ascites tumour cells by fractionated hydrolysis and measured by liquid scintillation. It was found that the rates of RNA and DNA depolymerisation and of DNA depurination depended on temperature in the same way. The DNA extraction patterns retained their form when the temperature was varied. When the hydrolysis was performed in decreasing acid concentrations, however, there was a concomitant change in the form of the depolymerisation pattern. This change affects the amount of aldehyde groups available for dye-binding with the Feulgen method after the optimal hydrolysis time. The alteration in shape of the Feulgen curve is discussed and supposed to be due to an increased interaction between DNA and other macromolecules. It is suggested that this interaction may be useful in detecting differences in chromatin stability between cells which differ in gene activity.