Effects of l,3-Bis(2-chloroethyl)-l-nitrosourea and Related Compounds upon the Synthesis of DNA by Cell-free Systems1
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چکیده
Incubation of crude enzyme preparations from leukemia L1210 ascites cells with l,3-bis(2-chloroethyl)-l-nitrosourea (BCNU) caused decreases in the DNA nucleotidyltransferase activity. l-(2-Chloroethyl)-3-cyclohexyl-l-nitrosourea was as active as BCNU, but l-(2-chloroethyl)-l-nitrosourea and 1methyl-1-nitrosourea were much less active. 2-Chloroethyl isocyanate was about equal to BCNU in activity, and this fact is consistent with the possibility that a major portion of the observed inhibitory action of BCNU is due to the 2-chloroethyl isocyanate generated from it. Incubation of commercial DNA with BCNU did not signifi cantly alter the activity of the DNA as a primer for the crude DNA nucleotidyltransferase system. Incubation of intact L1210 ascites cells with 2.5 X 10~3 M
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