When thymine auxotrophs are grown in the presence of methyl labelled [3H] or [14C] thymine which has been stored at 4 degrees C, two classes of material are labelled which are not DNA. One class sediments on neutral sucrose gradients with spontaneously single stranded Okazaki pieces, is unstable in alkali, migrates on alkaline gels as very small material and is digested by ribonucleases and mic...

We have studied the generation of reactive oxygen species during the metabolism of a carcinogen, benzo[a]pyrene, by human mammary epithelial cells. We have quantitated the production of one type of oxidative DNA damage, thymine glycols, by using a monoclonal antibody specific to this base modification. Thymine glycols were produced in DNA in a dose-dependent manner after exposure of human mamma...

In 1954, Cohen and Barner discovered that a thymine auxotrophic (thyA) mutant of Escherichia coli undergoes cell death in response to thymine starvation. This phenomenon, called thymineless death (TLD), has also been found in many other organisms, including prokaryotes and eukaryotes. Though TLD has been studied intensively, its molecular mechanism has not yet been explained. Previously we repo...

Stokes (1944) reported the replaceability of folic acid by thymine for Streptococcus lactis strain R as well as other folic-acid-requiring streptococci, and Fink et al. (1954) noted that high concentrations of recrystallized dihydrothymine supported growth of Streptococcus faecalis (ATCC 8043) deficient in both folic acid and thymine. The question arose, however, as to whether the latter respon...

The intraoellular concentration of thymidine triphosphate has been measured in thymine requiring mutants of Escherichia co&i K12 and E. coli 15, and compared with that in non-mutant strains using thymine, thymidine and a mixture of thymine and deoxyguenosine, in the growth medium. The data show (1) that the thymidine triphosphate concentration rises as the thymine concentration in the growth me...

5-Bromodeoxyuridine (BrUDr) is an effective inhibitor of the growth of E. coli and Lactobacitti, and this growth inhibition can be reversed by thymidine (1-3). There is evidence that this thymidine analog can replace the thymine of both E. coli and bacteriophage deoxyribonucleic acid (DNA) on an equimolar basis (7, 11, 12). In E. coli, nearly 50 per cent of the thymine can be replaced. Whereas ...

Cyclobutane thymine dimers, the major photoproducts produced in UV-irradiated DNA, are the main causative agents for mutagenesis and skin cancer. This lesion can also be initiated under UVA radiation, involving triplet–triplet energy transfer mechanism from a photosensitizer to the thymine nucleobase. According to previous reports, only photosensitizers with a triplet state energy >270 kJ mol 1...

It has been clearly established (1, 2), through the use of N16-labeled material, that the utilization of free thymine for the synthesis of deoxyribonucleic acid (DNA) by the rat is extremely limited. However, these studies afforded but little information concerning the rate and extent of the metabolism of thymine. In the experiments reported here, thymine-204 has been found to be more rapidly a...

Mutation can alter the structure of viral proteins to form different structure. Carbon distribution is responsible for these changes in structure. The carbon distribution in proteins of human Influenza A virus is analyzed here. Results reveal that the carbon contents are high in surface proteins, optimum in polymerase proteins and less in nuclear proteins. Polymerase proteins have better carbon...