Figure 6.

¹³C-Enrichment as a function of time in the methyl carbons of phosphatidylcholine from sycamore cells grown in the presence of 5 mm [¹³C]methanol. Relative ¹³C-enrichment was obtained for methyl carbon atoms from ¹³C-NMR spectra by the standard approach (phosphatidylcholine sample from sycamore cells with natural ¹³C-abundance versus phosphatidylcholine from sycamore cells grown with [¹³C]methanol). Cells were subcultured every 7 d in the presence of 5 mm methanol. The rate constant for choline enrichment roughly corresponds to the rate of membrane/cell doubling.