Quantitative Detection of Purines in Biologically-Relevant Films with TOF-Secondary Ion Mass Spectrometry

In purine-depleted environments, the de novo purine biosynthetic pathway is catalyzed to ultimately produce inosine monophosphate (IMP), a purine invisible using current optical microscopy methodology. These enzymes form a complex, termed the "purinosome," to replenish IMP levels. Before cellular chemical imaging may be applied to monitor the distributions and fluctuations in purine levels, it is necessary to develop a scheme to quantitatively detect purines. Here, IMP and other purines in biologically-relevant matrices have been detected quantitatively. These methods provide a TOF-SIMS protocol using C₆₀⁺ primary ions to determine the concentration of biomolecules in a cell such as HeLa at the nanomolar level.