DNA of Myxococcus phage MX-1. Pyrimidine isostichs and the recognition of a minor pyrimidine.

DNA was isolated from bacteriophage MX-1 and was hydrolysed with acids. Hydrolysis with 90% formic acid produced several interconvertable fluorescent artefacts. These substances were produced in greater quantity following hydrolysis with H2SO4. In the course of the course of the study it was found that DNA extracted from phage by 4-aminosalicylate and phenol contained 4-aminosalicylate and breakdown products derived from 4-aminosalicylate following acid hydrolysis. Pyrimidine oligonucleotides released by formic acid-diphenylamine hydrolysis were fractionated by two-dimensional paper chromatography and by ion-exchange chromatography. In this way, the pyrimidine isostichs were obtained and further fractionated. The distribution and with isostich patterns from a variety of DNA sources. MX-1 DNA was found to contain an unusually high frequency of cytosine-rich isostichs 5 and 6 and very low occurrence of the sequence R-Y-R. Based on its absorption spectrum and the fact that it can be labelled in vivo with [14C] orotic acid, we suggest that H-base is a pyrimidine.