DIFFERENTIAL AUTORADIOGRAPHY AND SPIN-COLUMN PURIFICATION OF SUGARS ON ACTIVATED-CHARCOAL

Methods utilizing activated charcoal for separating radiolabeled sugar s from each other and from water are described. The first method allev iates a practical limitation for use of tritiated sugars as a tracer i n plants. Tritium exchange with water can now be readily quantified be cause the method allows a more rapid separation of sugars and water th an has been previously described. A spin column containing activated c harcoal and powdered cellulose retained (>99%) sucrose during elution (>99%) of (H2O)-H-3 in water rinses. The retained sucrose could then b e eluted (95%) from the column by rinsing with aqueous methanol. The s econd method partially resolves another limitation in the use of radio labeled sugars as tracers in planta. We can now ascertain the spatial distribution of various radiolabeled sugars within particular organs. Charcoal filter paper was used to adsorb sucrose and hexose sugars for development of differential autoradiographs of sugars blotted from st em cross-sections of sorghum (Sorghum bi-color IL.] Moench). The hexos e sugars were selectively removed during rinsing of the charcoal paper in water. Autoradiography was performed before and after rinsing. The autoradiographic image obtained before rinsing reflected the presence on the blot of both radiolabeled sucrose and hexose sugars. In compar ison, the image obtained after rinsing no longer reflected the presenc e of radiolabeled hexose sugars. These methods help refine studies of carbon dynamics in plants by enhancing our ability to detect in plants movement of sugars through particular metabolic pathways and to detec t the spatial distribution within organs of particular radiolabeled su gars.