The structure of guanine propionate.

Guanine propionate was isolated as described previously (1). 7-Methylguanine and N*-methylguanine were gifts from Dr. Gertrude Elion, Wellcome Research Laboratories (Tuckahoe, New York). Phosphate was determined according to the method of Fiske and SubbaRow (2). The orcinol determination of pentose was carried out by the procedure of Kerr et al. (3). The Pauly reaction was run according to the procedure of MacPherson (4). The assay by the phenol reagent was that of Folin and Ciocalteau (5). L-Lactic acid was assayed with crystalline rabbit muscle lactic dehydrogenase (Boehringer) . The conditions of the assay were according to Horn et al. (6). Total lactic acid was determined by the method of Barker and Summerson (7). The preparation of the chromatographic solvents designated with numbers is described in the previous paper (1). A quantitative measure of amino acids after paper chromatography was obtained by spraying with 1 y0 ninhydrin and 1% 2,61utidine in 95% ethanol and developing the color at 60’ for 30 minutes in an atmosphere saturated with water vapor (8). The colored area was cut out and eluted with 70% ethanol and the optical density of the resulting solution determined at 540 rnp. The standard error of deviation was less than &5%. n-Alanine was determined by coupling partially purified n-amino acid oxidase (9) with lactic dehydrogenase and DPNH and following the decrease in optical density at 340 mp. Carboxylic acids were separated by paper chromatography with n-propanol-water-diethylamine in the proportions 85: 15:l (volume for volume). Rp values for several acids in this solvent were: acetic, 0.53; pyruvic, 0.16; lactic, 0.52; cu-ketoglutaric, 0.36; succinic, 0.28; fumaric, 0.30; and malic, 0.18. As little as 0.2 pmole of the compounds was detected by spraying the paper lightly with 0.2 or 0.5% bromocresol green in 95% ethanol (10). Spectrophotometric Determination of Ionizing Groups-Two 5ml solutions of the compound under investigation were acidified