UVPD spectroscopy of differential mobility-selected prototropic isomers of protonated adenine

Two prototropic isomers of adenine are formed in an electrospray ion source and are resolved spatially in a differential mobility spectrometer before detection in a triple quadrupole mass spectrometer. Each isomer is gated in CV space before being trapped in the linear ion trap of the modified mass spectrometer, where they are irradiated by the tuneable output of an optical parametric oscillator and undergo photodissociation to form charged fragments with m/z 119, 109, and 94. The photon-normalised intensity of each fragmentation channel is measured and the action spectra for each DMS-gated tautomer are obtained. Our analysis of the action spectra, aided by calculated vibronic spectra and thermochemical data, allow us to assign the two signals in our measured ionograms to specific tautomers of protonated adenine.

Automated summary

Two prototropic isomers of adenine were analyzed using a combination of a differential mobility spectrometer, mass spectrometer, and photodissociation method, resulting in the determination of action spectra for each isomer. The study successfully assigned the two signals in the measured ionograms to specific tautomers through analysis of the action spectra, calculated vibronic spectra, and thermochemical data.