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Abstract

The nucleic acid of Pseudomonas acidovorans bacteriophage 0W-14 was isolated and characterized as double-stranded DNA. Unlike normal DNA molecules, a great disparity was found between the moles % GC calculated from CsCl buoyant density gradient data and Tm determination. The buoyant density in neutral CsCl was 1.666 g/cm³ (4.5 moles % GC) and the Tm in SSC was 99.3 C (72.9 moles % GC). The buoyant density in Cs₂SO₄ was also unusually low (1.415 g/cm³). Acid hydrolysates contained five bases: adenine, guanine, cytosine, thymine and an unknown. The concentration of thymine was approximately half that of adenine. Assuming that the unknown base made up for this deficiency in thymine, the moles % GC in 0W-14 DNA was calculated to be 56.2. The unknown base, a pyrimidine, was isolated and purified by column chromatography. It was characterized by chemical analysis, NMR, IR and mass spectroscopy as N-thyminyl-putrescine: [5-(4-aminobutylamino methy1)uracil]. Chemical synthesis confirmed the structure of the compound.