Stable isotope labelling method for studies of saccharide metabolism in Agardhiella subulata

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Stable isotopes are preferable in many ways to radioactive isotopes for metabolic studies designed to elucidate biosynthetic pathways. We have developed the methodology to utilize 13C-labelled compounds in tracer studies of saccharide metabolism in the red algae. Cultures of Agardhiella subulata were pulse-chase labelled with 13C02 and 12C02. Gas chromatography/mass spectrometry (GC-MS) and 13C-NMR provided for positive identification of labelled carbohydrate metabolites. In addition, GC-MS can be used to profile the monosaccharide composition of algal species and combined GC-MS and 13C-NMR can disclose which carbon(s) is (are) labelled and the extent of labelling. In 13C02 incubated plants, the label is clearly detected in floridoside and floridean starch. After chasing the labelled alga with 12CO2 for three days or storing the pulse-chase labelled alga in darkness for 6 days, labels disappeared from both floridoside and starch and the contents of these two carbohydrates became very low. More detailed biochemical analysis is being continued to identify labelled cell wall polysaccharides and/or their precursors. © 1983 Kluwer Academic Publishers.

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