Fig. 2.

¹³C incorporation level in aromatic side-chains resulting from different amounts of 1¹³C erythrose in the medium. Incorporation in Phe ε* (green), Tyr ε* (blue) and Trp ζ2 red are shown in % relative to fully ¹³C enriched glucose. Solid lines are single exponential fits. Note that for Phe and Tyr the referencing is for two carbons (1 and 2, represented by asterisk), since the aromatic rings undergo fast ring-flips on the NMR time-scale