Abstract: THE INQUIRY ON THE SOURCE OF OPTICAL ACTIVITY Ⅶ.STUDY ON THE STEREOSELECTIVE GAMMA RADIOLYSIS OF LEUCINEENANTIOMERSZHOU YURONG；LU MINGIAN WANG WENQING；WU JILAN （Department of Technical Physies,Peking University，Beijing，100871）ABSTRACTγ-irradiation of D，L-amino acids introducing the stereoselective radiolysis is an openquestion concerning origin of optical activity．Merwitz（1976）reported that the rate of theγ-ray induced solid state decarboxylation of ~(14)C labeled D-phenylalanine was 2．7 timesgreater than that of L-phenylalanine. Norden（1985）reported that the decarboxylation ofsublimed D－and L-leucine by nonpolarized γ-rays gave different yields ，with a A_D／A_L for~(12)CO_2 cleavage ratio of 2．Since impurities have significant effect on the stop or the enhance-ment of chain reaction，the conclusion from the separatively purified amino acids is howeverdubious. In the paper，sublimed D-，L-leucine and the D，L-racemate are irradiated by ~(60)Coγ-ray under strictly controlled condition. Chirasil-val capillary column gas chromatography isused to determine the peak ratios of D，L-leucine，D-and L- leucine. From the results ofTable 1 and 2， the changes of G values with dose are nearly the same. The relative yields ofthe radiolysis gas products（H_2，CO_2，NH_3）of D-and L-leucine are detected．The experimen-tal data show that γ-irradiation induced degradations of D-and L-leucine give generally equalamount of gas H_2，CO_2，and NH_3， indicating no stereoselective effects observed. Key words Garnma ray D，L-leucine Relative yields of H_2，CO_2，NH_3 Chirasil-val capillary column