Fig. 5. 13C NMR spectra (quaternary region) of mature green tomato fruit pericarp extracts. (a) Conventional (non-hyperpolarised) spectrum of 20 mg extract (prepared from 20 mg lyophilized grounded tissue) dissolved in 700 μL D2O, recorded with 1024 scans (11 h 45 min) at 700 MHz with a cryogenic probe. (b) Spectrum of an identical extract recorded with D-DNP combined with CP. The extract was first dissolved in a 200 μL mixture of H2O/D2O/glycerol-d8 (2 : 3 : 5) doped with 25 mM TEMPOL, then polarized for 30 min at 1.2 K and 6.7 T, and finally dissolved with 5 mL of hot D2O and transferred in about 10 seconds to a 500 MHz spectrometer equipped with a cryogenic probe. (c) Same as (b), but the tomato extract was replaced by a control sample prepared under strictly identical conditions without any biological material. The hyperpolarized spectra result from the sum of six consecutive acquisitions using 30° pulses spaced by 7.7 s. *Indicates the signal of a 13C-labeled pyruvate impurity from the D-DNP setting. Cit: citrate; GABA: γ-aminobutyrate; Gln: glutamine; Mal: malate. Reproduced from ref. 102 with permission from the Royal Society of Chemistry.
