APPENDIX
Yield of Ultraviolet
Light-induced Pyrimidine Dimers in the DNA of Bacteriophage $X174 .J. ,J. CORNELIS Departement de Biologic Molkculaire Universite’ Libre de Bruxelles Rue des Cheveaux 67 1640 Rhode St &n&w. Bdgiurn
Phage 4x1’74 DNA was L3H]thymidine-labeled at a specific radioactivity of approximately 10e5 cts/min per molecule. Radioactive labeling, phage purification, conditions of U.V. irradiation and phage DNA ext,ract,ion procedures are described in Materials and Methods in the main text. The proportion of thymine in thyminecontaining, cyclobutane-type pyrimidine dimers was determined as described by Carrier & Setlow (1971). Figure Al shows that the proportion of thymine in dimers is a linear function of the u.v.-fluence up to about 50 Jme2, with an initial slope of 0.656 >: 10m6 thymine-containing dimers per Jn-“. A somewhat lower value was obtained by David (1964), possibly due to the differences in the source of U.V. light and in dosimetry. The number of thymine-containing dimers per $X174 DNA was h h calculated taking the TT : CT : CC ratios as determined by Setlow & Carrier (1966) for
Fluence
FIG. Al. Propdim
(i mm21
uf thyminc ill dirnars in +X174 DNA plotted as a furlctiwl of u.v.-flamce. 111
112
P.
CAILLET-FAUQUET
El’
,4L
an (A + T)-rich DNA at low fluences, 5400 as the number of nucleotides per genome. 33% of which are thymine (Sinsheimer, 1959). Our estimate of the yield of all pyrimidine dimers in 4X174 DNA is 7.92~ 10e2 per genome per Jrnm2 in the dose range of the linear response in Figure Al. REFERENCES Carrier, W. L. & Setlow, R. B. (1971). Methods Enzymol. 21, 230-237. David, Ch. N. (1964). 2. Vererbungsl. 95, 318-325. Setlow, R. B. & Carrier, W. L. (1966). J. Mol. Biol. 17, 237-254. Sinsheimer, R. L. (1959). J. Mol. BioZ. 1, 43-53.
Yield of Ultraviolet
Light-induced Pyrimidine Dimers in the DNA of Bacteriophage $X174 .J. ,J. CORNELIS Departement de Biologic Molkculaire Universite’ Libre de Bruxelles Rue des Cheveaux 67 1640 Rhode St &n&w. Bdgiurn
Phage 4x1’74 DNA was L3H]thymidine-labeled at a specific radioactivity of approximately 10e5 cts/min per molecule. Radioactive labeling, phage purification, conditions of U.V. irradiation and phage DNA ext,ract,ion procedures are described in Materials and Methods in the main text. The proportion of thymine in thyminecontaining, cyclobutane-type pyrimidine dimers was determined as described by Carrier & Setlow (1971). Figure Al shows that the proportion of thymine in dimers is a linear function of the u.v.-fluence up to about 50 Jme2, with an initial slope of 0.656 >: 10m6 thymine-containing dimers per Jn-“. A somewhat lower value was obtained by David (1964), possibly due to the differences in the source of U.V. light and in dosimetry. The number of thymine-containing dimers per $X174 DNA was h h calculated taking the TT : CT : CC ratios as determined by Setlow & Carrier (1966) for
Fluence
FIG. Al. Propdim
(i mm21
uf thyminc ill dirnars in +X174 DNA plotted as a furlctiwl of u.v.-flamce. 111
112
P.
CAILLET-FAUQUET
El’
,4L
an (A + T)-rich DNA at low fluences, 5400 as the number of nucleotides per genome. 33% of which are thymine (Sinsheimer, 1959). Our estimate of the yield of all pyrimidine dimers in 4X174 DNA is 7.92~ 10e2 per genome per Jrnm2 in the dose range of the linear response in Figure Al. REFERENCES Carrier, W. L. & Setlow, R. B. (1971). Methods Enzymol. 21, 230-237. David, Ch. N. (1964). 2. Vererbungsl. 95, 318-325. Setlow, R. B. & Carrier, W. L. (1966). J. Mol. Biol. 17, 237-254. Sinsheimer, R. L. (1959). J. Mol. BioZ. 1, 43-53.
