Abstract
The thiol content of deoxyribonucleoproteins (DNP), isolated from Ehrlich ascites tumor cells by 1 M NaCl extraction, was measured by amperometric titration with AgNO 3 before and after reduction of the disulphide bonds with NaBH 4. The amount of -SH and SS groups was 59 μmoles and 19 μmoles g protein, respectively. About 20 μmoles - SH g protein of the total thiol content of DNP could be extracted with a weak acid after reduction of the disulphide bonds. In addition to proteins, the acid soluble fraction contained also glutathione and unidentified -SH containing polypeptides with molecular weights larger than glutathione. The radioprotective compound cysteamine was found to form mixed disulphides with the -SH groups of DNP, and to reduce existing disulphide bonds and thereby release DNP-bound peptides. The possible importance of -SH and disulphide groups in DNP for radiation protection is discussed.
Published Version
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