Quantitation and identification of carbon-13 isotopometers by homonuclear polarization transfer NMR experiments

The simplest pulse sequence (π/2)x-τ-(π/2)y (Acquisition) for nuclear spin polarization transfer is used in a selective fashion: transfer only flows from a nucleus A to any nucleus X J-coupled to A, provided that the carrier frequency coincides with the A resonance and that τ is slightly varied around a properly chosen value, relevant free induction decays being co-added. According to the value selected for τ (1/2J or 1/4J, J: one bond carbon-carbon coupling constant), it proves possible to sort out and compare subspectra pertaining to isotopomers involving one, two, three, and four consecutive 13C. The method has been applied to an extract of mycelium grown on a medium containing 13C-labeled acetate, with the aim of delineating metabolic pathways from proportions of the detected isotopomers. 24 refs.; 2 figs.; 1 table