Methylation patterns of transfer RNA from ascites hepatomas

4,6-Diaminopyrimidine-2(1H)-thione hemihydrate: a three-dimensional hydrogen-bonded framework

In the title compound, C(4)H(6)N(4)S·0.5H(2)O, there are two independent pyrimidinethione units, both of which lie across mirror planes in the space group Cmca. Hence, the H atoms bonded to the ring N atoms in each molecule are disordered over two symmetry-related sites, each having an occupancy of 0.5. The water molecule lies across a twofold rotation axis parallel to [010]. The molecular components of (I) are linked by seven independent hydrogen bonds, of N-H···N, N-H···S, N-H···O and O-H···S types. A combination of disordered N-H···N hydrogen bonds and ordered N-H···S hydrogen bonds links the pyrimidinethione units into a continuous tubular structure. The water molecule acts as both a double donor of hydrogen bonds and a double acceptor, forming hydrogen bonds with components of four distinct pyrimidinethione tubes, thus linking these tubes into a three-dimensional structure.

Brain transfer RNA. II. Analysis of modified nucleosides

Transfer RNAs were isolated from rat and calf brains and their nucleosides were analysed by tritium derivative technique. Qualitative changes in the minor nucleoside components were compared on the fluorograms which showed differences in the intensities of spots. Cerebellar and cortical tRNAs were also compared, but revealed no significant quantitative differences in their methylated constituants despite 60% higher methyltransferase activity observed in cerebellum compared to cerebral cortex. An overall similarity was noticed between the relative proportions of the major and minor nucleosides of tRNAs derived from rat or calf brain, expressed as mol%. Brain tRNA was also analysed by two-dimensional polyacrylamide gel electrophoresis which showed qualitative and quantitative changes during postnatal development.

On the methylated purine content of tRNA present in tumours

The methylated purine content of tRNA bulk extracted from human hepatomata has been compared with that in normal human liver. The analyses were carried out with the aid of ion-exchange chromatography. The molar proportions of 5 bases detected in acid hydrolysates of tumour tRNA (N(2)-methylguanine, 1-methylguanine, 7-methylguanine, N(2)-dimethylguanine and 1-methyladenine) were not abnormally elevated.