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Acid Deoxyribonuclease (DNase II) in Rat Liver Cell Nuclei Isolated in the Presence of Ca++

出版	U.S. Naval Radiological Defense Laboratory, 1963
URL	http://books.google.com.hk/books?id=mnCi5bzYA18C&hl=&source=gbs_api
EBook	FULL_PUBLIC_DOMAIN

註釋The failure of many investigators to find more than traces of deoxyribonuclease activity in the nuclei of cells has led to difficulties in attempting to ascribe a physiological role to this enzyme in living cells. Reinvestigation in this laboratory disclosed that nuclear fractions centrifugally separated from rat liver homoge nates in isotonic sucrose or in water, containing in each case 1.8 x 10 to the -3 power M CaCl(2) and washed repeatedly in the same media, retained a considerable amount of acid DNase activity. Similarly prepared nuclear fractions using calcium-free media lost nearly all of their DNase activity. This retention of activity in the presence of calcium was shown to be neither co-sedimentation of unbroken cells or of lysosomes with the nuclear fraction nor precipi tation of soluble e in the presence of calcium. The nuclear-bound enzyme was active under conditions which were shown not to remove it from the nuclei. (Author).