Acid-soluble metabolites of adenine-2-14C-adenine-8-14C in 2,6-diaminopurine-sensitive and 2,6-diaminopurine-resistant L strain mouse cells

The acid-soluble metabolites of adenine-2-14C and adenine-8-14C formed by 2,6-diaminopurine-sensitive and 2,6-diaminopurine-resistant L strain mouse cells have been separated by ion-exchange resin and paper chromatography. At least 20 acid-soluble metabolites were formed in 2,6-diaminopurine-sensitive cells. Significant, but much smaller amounts of some of these metabolites were also synthesized in 2,6-diaminopurine-resistant cells.

Single-stranded, adenine-rich RNA from purified reoviruses

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Ribonucleic acid synthesis during morphogenesis in Myxococcus xanthus

Ribonucleic acid synthesis was measured during the morphogenesis of Myxococcus xanthus. After induction of microcyst formation by the addition of glycerol to an exponential culture, net ribonucleic acid (RNA) synthesis was immediately terminated (measured either chemically or by the accumulation of acid-insoluble radioactivity). Extensive RNA turnover did take place, however, including RNA made both before and after induction. Sucrose gradient centrifugation revealed that ribosomes and ribosomal RNA were synthesized during microcyst formation even though there was no net RNA synthesis. Base analyses of the total RNA of vegetative cells and 120-min microcysts were indistinguishable.

Determination of the base composition of deoxyribonucleic acid by measurement of the adenine-granine ratio

A method is described for determination of the base composition (as guanine+cytosine or adenine+thymine content) of DNA by accurate measurement of the adenine/guanine ratio. The DNA is hydrolysed with 0.03n-hydrochloric acid for 40min. to release the purines. The hydrolysate is subjected to ion-exchange chromatography on Zeo-Karb 225. Apurinic acids are eluted with 0.03n-hydrochloric acid and then guanine and adenine are eluted separately with 2n-hydrochloric acid. Guanine and adenine are each collected as a single fraction, and the amount of base in each case is determined by measuring the volume and the extinction at suitable wavelengths. For use in the calculations, millimolar extinction coefficients in 2n-hydrochloric acid of 12.09 for adenine at 262mmu, and 10.77 for guanine at 248mmu, were determined with authentic samples of bases. The method gives extremely reproducible results: from 12 determinations with calf thymus DNA the adenine/guanine molar ratio had a standard deviation of 0.011; this corresponds to a standard deviation in guanine+cytosine content of 0.2% guanine+cytosine.

Hydroxyapatite fractionation procedures in the study of the mammalian genome

Three methods of fractionating DNA are described, in which DNA fragments are separated on the basis (1) of their base composition, (2) of the ability of denatured DNA to renature after incubation, and (3) of the presence of intrastrand secondary structure in denatured DNA. The ability of some of these fractions to form specific duplexes with whole denatured DNA isolated from the same and from a different mammal has been investigated. The results are presented to demonstrate how the fractionation procedures described may provide new information about the organization of the mammalian genome.