Figure 1.

Representative in vivo ¹³C-NMR spectra (expanded scale from 10–65 ppm) obtained from sycamore cells. The spectra, recorded at 20°C, are the results of 3,600 transients (60 min). Cells (9 g wet weight) were taken from a standard exponentially growing suspension culture, packed in a 25-mm NMR tube as described previously (Aubert et al., 1996), and perfused with a Mn²⁺-free culture medium containing 5 mm Suc. A, Control cells at pH 6.0; B, cells incubated for 2 d with 5 mm [¹³C]methanol at pH 6.0. Note that the methyl carbons resonance of phosphatidylcholine is broadened because this polar lipid is not free to move. In addition, signals from Ser (C-3, ¹³C-enriched) and methyl-β-d-glucopyranoside (CH₃, ¹³C-enriched) overlapped in ¹³C-NMR spectra of intact cells (compare with Fig. 2). Part of the amino acid and organic acid methylene groups are shown on expanded scales (magnification, ×8). Peak assignments are as follows: MeG, [¹³C]methyl-β-d-glucopyranoside; PC, [¹³CH₃]phosphatidylcholine; ¹³C-Me, [¹³C]methanol; cit, citrate; mal, malate; suc, succinate; Met, [¹³CH₃]Met; S, Suc.