Since the first report on the presence of the modified nucleoside N6-(A'-isopentenyl) adenosine (A~-IPA) in yeast tRNA
(1,2) several other nucleosides with related structures have been isolated and characterized from tRNA's of various species (3,4). All these compounds have been shown to possess potent cytokinin activity, the most active of which are zeatin, N6-(4-hydroxy-3-methylbut-2-trans-enyl) adenine, and the parent compound, AZ-IPA. The double-bond isomer of the parent compound, N6-( A3-isopentenyl) adenosine, has been synthesized and shown to be almost equally as potent a cytokinin
(5). Isolation and characterization of these compounds have relied mainly on bioassays and the usual chromatographic procedures in combination with mass spectrometry. However, in the case of very closely related structures, these procedures are inadequate (4). Positive identification by mass spectrometry depends on the purity of the sample. It is necessary, therefore, to have a separation method with increased resolving power. Gas-liquid chromatography (GLC) of nucleosides has been shown to be feasible (6-8). Recently this method was applied to the identification of isoprenoid nucleosides in tRNA's from several species &tm *
The present report describes the separation of the two double-bond isomers, AZ-IPA and AS-IPA, by gas-liquid chromatography and characterization of their TMS derivatives by mass spectrometry. MATERIALS AND METHODS N,O-Bis (trimethylsilyl) trifluoroacetamide (BSTFA) was obtained from Regis Chemical Co., Chicago, Illinois. Dow-Corning silicone grease DC-11 and Gas Chrom Q were purchased from Kenscott Ltd.