Some simple thin-layer chromatographic systems for the separation of purines and purine nucleosides.

Studies on nucleic acid metabolism often require the analytical separation of nucleic acid derivatives and are facilitated by chromatographic methods which are rapid and convenient. Column chromatography on ion exchange resins (1)) paper chromatography (2)) and paper electrophoresis (3) are among the methods used routinely for such separations. Even though these techniques have been employed widely, they require lengthy development times and specialized equipment. Thin-layer chromatography (tic) also has been used for the separation of nucleic acid derivatives and has the advantages of simple and rapid development procedures combined with high resolution power (4-6). The separation of nucleotides on anion exchange celluloses has been particularly well developed, with polyethyleneimine-cellulose (PEI-cellulose) used extensively (7). A number of tic techniques also have been devised for the separation of nucleic acid bases and nucleosides. Most, of these employ cellulose layers although silica gel plates have been used as well (4-6). However, neither appears to be commonly used. Kolassa et al. (8) recently described several new silica gel systems for the chromatography of purine derivatives. These systems gave good separations but required running times of three to four hours in alcoholic solvents. We describe in this commmlication some simple tic silica gel systems which employ chloroform-containing solvents and require development times of under one hour. These have been used routinely by us for the separation of purines and purine nucleosicles in metabolic studies with 9-p-n-arabinofuranosylaclcnine (Ara-f-Ade) Methods. Prescored 20 X 20 cm tic plates with a 250 pm layer of silica gel GF254 (Merck) were obtained from Analtech, Inc., Newark, DE. Plastic sheets, 20 X 20 cm, coated with 100 pm of PEI-cellulose (PEI-cellulose, Macherey Nagel 300) were obtained from Brinkmann Instruments, Inc., Des Plaines, IL, and were converted to the borate form as described by Schrecker et al. (9). The following chloroform-containing solvents were prepared by mixing chloroform, methanol, and either 37~ acetic acid or 3% ammonia