Quantative measurements of the glucose analogue, 2-deoxyglucose (2DG), and its phosphorylated metabolite (2-deoxyglucose-6-phosphate (2DG-6-P)) are critical for the measurement of glucose uptake. While the field has long identified the need for sensitive and reliable assays that deploy non-radiolabled glucose analogues to assess glucose uptake, no analytical MS-based methods exist to detect trace amounts in complex biological samples. In the present work, we show that 2DG is poorly suited for MS-based methods due to interfering metabolites. We therefore developed and validated an alternative C18-based LC-Q-Exactive-Orbitrap-MS method using 2-fluoro-2-deoxyglucose (2FDG) to quantify both 2FDG and 2FDG-6-P by measuring the sodium adduct of 2FDG in the positive mode and deprotonation of 2FDG-6-P in the negative mode. The low detection limit of this method can reach 81.4 and 48.8 fmol for both 2FDG and 2FDG-6-P, respectively. The newly developed method was fully validated via calibration curves in the presence and absence of biological matrix. The present work is the first successful LC-MS method that can quantify trace amounts of a nonradiolabeled glucose analogue and its phosphorylated metabolite and is a promising analytical method to determine glucose uptake in biological samples.
Fragmentation of Oligosaccharides from Sodium Adduct Molecules Depends on the Position of N-Acetyl Hexosamine Residue in Their Sequences in Mass Spectrometry
