B. All m/z features detected from iRBC extracts plotted as the log2 ratio of their abundance detected in 13C-glucose versus 12C-glucose conditions. 859 m/z features (from a total 33,691 m/z features identified) were significantly altered in 13C versus 12C samples of iRBC. Highlighted in black is a single m/z feature (m/z 275.0167). 