Figure 3.

Confirmation via isotope labeling that the putative glyceraldehyde-3-phosphate peak is from in-source fragmentation. (A) Schematic of upper glycolytic intermediates in yeast cells grown on 1,2-¹³C₂-glucose. (B). The negative ionization mode-extracted ion chromatogram for unlabeled and ¹³C₂ hexose-phosphate and triose-phosphate channels. Dihydroxyacetone-phosphate (DHAP) shows up in both unlabeled and ¹³C₂ channels, but the leftmost “triose-phosphate” peak only shows up in the unlabeled channel, confirming that this peak is the in-source fragmentation of the last three carbons of glucose-6-phosphate. Method A has been used throughout this figure.