Effect of gamma irradiation on DNA and nucleohi ~ ton ~ in vitro under - - - physiological conditions

~ntose sugar and histones have been shown to deplete from DNA and nucleohi stone (DNH) on gamma irradiation in a dose-dependent and biphasic manner in EDTA buffer while depletion of inorganic phosphorus (Pi) is a linear function of dose. In DNA, the depletion of sugar is more compared to that of Pi for 100 Gy. In DNH for 100 Gy the order of depletion is hitone > sugar> Pi . With 0.9% sodium chloride as solvent, for a total dose of 100 Gy, variation in the amount of sugar and protein depletion were observed when the dose rates were varied. From DNH at higher dose rate of radi ation (i.e. 2.92 Gy/sec), sugar depletion was 4 times and total histone depletion was 2.S times than that for lower dose rate (i.e. 0.01S6 Gy/sec). Pi depletion was found to be not dependent upon dose rate. Percentage hyperchromicity and hyperlluorophoricity for DNH decreased with increase in concentration both in 0.9% sodium chloride and standard saline citrate in the pH range 6.14 to 7.67 , the values being higher in the former than in latter. DNA also showed consistent hyperchromicity with increase in radiation dose in EDT A buffer at ionic strength of 2.00. ) • 1 ,.