On the role of phosphate and phosphoprotein in thymocyte interphase death

Radiation-induced Liberation of DNA-protein Complex in Rat Spleen

“…But an early report of post-irradiation decrease in the histone-to-DNA ratio in spleen and thymus (Ernst 1962) has not yet been confirmed (Telia, Reuter, Gerber and Kennes 1969) . Moreover, phosphorylation of histones, which may cause a dissociation of histones from the DNA in nucleoprotein, is depressed after irradiation (Ord andStocken 1966, Betel, Appelman andGraver 1970) . The productive mechanisms of `free DNA' production remain unknown .…”

“…The clear supernatant fluid containing `free DNA' and other macromolecules, such as RNA and protein, was subjected to the analytical procedures . The method of equilibrium centrifugation in CsC1 density gradients was used ; the step gradient method (Brunk and Leick 1969), which allows a reduction in centrifugation time, was applied for characterization of the so-called ' free DNA ' . Centrifugation was performed at 37 000 rev/min for 18 hours at 20°C with the Spinco SW 39 rotor .…”

“…Fractions (usually 25 to 35) were then collected from the bottom of the tubes for determination of the density of CsCl and the amount of DNA . The DNA content of each fraction was estimated at 600 mµ by the method of Burton (1956) after extraction with 0 . 3 N PCA at 90°C for 15 min .…”