FIGURE 6.

Potential of dissolution dynamic nuclear polarization (d-DNP) for highly sensitive ¹³C NMR metabolomics at natural abundance. (A) d-DNP experimental scheme, where the sample is first hyperpolarized at liquid He temperature in a glass-forming solvent by microwave irradiation of free radicals, then rapidly transferred through a magnetic tunnel to a classical NMR spectrometer where conventional detection occurs. (B) First application of this experimental scheme in a natural abundance ¹³C metabolomics study, reported in 2020 by Dey et al. Scores plot of the principal component analysis (PCA) obtained from 40 spectral buckets from hyperpolarized ¹³C spectra of 16 tomato fruit extracts at different ripening stages (green vs red). Integrals were normalized to Na-TSP-d₄ as an internal reference and to the weight of the sample used for extraction. Mean centering and unit variance scaling were used in PCA. (B) Reproduced from (Dey et al., 2020).