Published Papers

Studies on the Chemical Nature of the Substance Inducing Transformation of Pneumococcal Types: Induction of Transformation by a Desoxyribonucleic Acid Fraction Isolated from Pneumococcus Type III. January 1944.

Page 11 [146]

< Previous Page     Page 10 [145]

Back to Document Index Studies on the Chemical Nature of the Substan...

Next Page > Page 12 [147]

Title:	Studies on the Chemical Nature of the Substance [11 of 23]
Alternative Title:	Induction of Transformation by a Desoxyribonucleic Acid Fraction Isolated from Pneumococcus Type III
Creator:	Avery, Oswald T.
Contributor:	MacLeod, Colin M.
Publisher:	Journal of Experimental Medicine
Date:	1944-01-00
Subject:	Cellular signal transduction
Description:	From the Journal of Experimental Medicine Vol. 79, No. 1.
Type:	Text
Format:	text/plain
Language:	en
Identifier:	avery-pg11.jpg
Source:	Master scanned with Epson GT-10000+ flatbed scanner at 600 dpi.
Rights:	http://osulibrary.orst.edu/specialcollections/coll/pauling/dna/copyright.html
Full Text:	OSWALD T. AVERY, COLIN DI. MACLEOD, AND MACLYN MCCARTY‘47 preparations shown to contain an enzyme capable of depolymerizing authentic samples of desoxyribonucleic acid were found to inactivate the transforming principle. Greenstein and Jenrette (18) have shown that tissue extracts, as well as the milk and serum of several mammalian species, contain an enzyme system which causes depolymerization of desoxyribonucleic acid. To this enzyme system Greenstein has later given the name desoxyribonucleodepolymerase (19). These investigators determined depolymerase activity by following the reduc- tion in viscosity of solutions of sodium desoxyribonucleate. The nucleate and enzyme were mixed in the viscosimeter and viscosity measurements made at intervals during incubation at 30°C. In the present study this method was used in the measurement of depolymerase activity except that incubation, was carried out at 37°C. and, in addition to the reduction of viscosity, the action of the enzyme was further tested by the progressive decrease in acid precip- itability of the nucleate during enzymatic breakdown. The effect of fresh normal dog and rabbit serum on the activity of the transforming substance is shown in the following experiment. Sera obtained from a normal dog and normal rabbit were diluted with an equal volume of physiological saline. The diluted serum was divided into three equal portions. One part was heated at 65°C. for 30 minutes, another at 60°C. for 30 minutes, and the third was used unheated as control. A partially purified prepara- tion of transforming material which had previously been dried in the lyophile appara tus was dissolved in saline in a concentration of 3.7 mg. per cc.‘.0 cc. of this solution was mixed with 0.5 cc. of the various samples of heated and unheated diluted sera, and the mixtures at pH 7.4 were incubated at 37°C. for 2 hours.šfter the serum had been allowed to act on the transforming material for this period, all tubes were heated at 65°C. for 30 minutes to stop enzymatic action.¬erial dilutions were then made in saline and tested in triplicate for transforming activity according to the procedure described under Method of titration. The results given in Table III illustrate the differential heat inactivation of the enzymes in dog and rabbit serum which destroy the transforming principle. From the data presented in Table III it is evident that both dog and rabbit serum in the unheated state are capable of completely destroying transforming activity. On the other hand, when samples of dog serum which have been heated either at 60°C. or at 65°C. for 30 minutes are used, there is no loss of transforming activity.­hus, in this species the serum enzyme responsible for destruction of the transforming principle is completely inactivated at 60°C. In contrast to these results, exposure to 65°C. for 30 minutes was required for complete destruction of the corresponding enzyme in rabbit serum. The same samples of dog and rabbit serum used in the preceding experiment were also tested for their depolymerase activity on a preparation of sodium desoxyribonucleate isolated by Mirsky from shad sperm.