Absolute Quantification of ppGpp and pppGpp by Double-Spike Isotope Dilution Ion Chromatography–High-Resolution Mass Spectrometry

N isotope dilution dimension. This double-spike IDMS method was applied to quantify the ppGpp and pppGpp in Escherichia coli and in a mutant strain deleted for gppA (encoding the ppGpp phosphohydrolase) before and after exposure of both strains to serine hydroxamate, known to trigger the accumulation of these nucleotides.