The pyrimidine analogs, 5-azaorotic acid (6 X 10@ M) and 5-azauracil (2 X 10@ M), caused approximately 50 per cent inhibition of the metabolism of orotic acid by cell free extracts from mouse liver or L5178Y leukemia cells. Seven other compounds of a total of 42 tested also caused at least 50 per cent inhibition at concentrations less than 2 X 10@ M. The primary site of action of the two symmet...

because of various interesting biological activities.1 The tautomeric proton is highly effective at making strong intermolecular hydrogen binding with other heteroatoms of molecules involved with biological activity. The title compound 3-amino-1,2,4-triazin-5(2H)-one (6-azaisocytosine, Fig. 1), an isosteric isomer of isocytosine, can exist in several tautomeric forms, which have been discussed ...

4-Amino-6-methyl- 1,2,4-triazine-3(2H)-thione-5-0ne (1) was condensed with propargyl bromidein the presence of sodium rnethoxide to afford 3-propargylmercapto- 4-arnino-6-rnethyl-1,2,4-triazin-5-one(2) . Transformation of the latter to 8-dihydro- 3-methyl-7-methylene-4-oxo-6H-[1,2,4]TRIAZINO [3,4-b] [1,3,4] thiadiazine (3) was performed under the condition of palladium (II) salt. Ring closu...

Cotton (Gossypium hirsutum L.) ovules grown in a defined nutrient medium undergo normal morphogenesis, including fiber production. In identical medium lacking boron, ovules callus and accumulate brown substances. Boron deficiency-like symptoms were induced by 6-azauracil and 6-azauridine in ovules growing in boron-sufficient media. Other nucleoside base analogs either reduced or had no effect o...

Uracil-DNA glycosylase was partially purified from HeLa cells. Various substrates containing [3H]dUMP residues were prepared by nick-translation of calf thymus DNA. The standard substrate was double-stranded DNA with [3H]dUMP located internally in the chain. Compared to the release of uracil from this substrate, a 3-fold increase in the rate was seen with single-stranded DNA, and a 20-fold redu...

Uracil-DNA glycosylase activities from etiolated Zea mays seedling nuclei and mitochondria were partially purified and characterized. Nuclei and mitochondria were separated using sucrose differential and step gradient centrifugation. Experiments with osmotically shocked organelles indicated that enzyme activity from mitochondria was soluble, whereas nuclear enzyme activity was only partially so...

Loss of function of S-II makes yeast sensitive to 6-azauracil. Here, we identified a multi-copy suppressor gene of this phenotype, termed SSM1 (suppressor of 6-azauracil sensitivity of the S-II null mutant 1), that encodes a novel protein consisting of 280 amino acid residues. Although both the SSM1 null mutant and the S-II/SSM1 double null mutant were viable under normal growth conditions, the...