Effect of Protonation on the Molecular Structure of Adenosine 5′-Triphosphate: A Combined Theoretical and Near Edge X-ray Absorption Fine Structure Study

[Image: see text] The present work combines the near edge X-ray absorption mass spectrometry of a protonated adenosine 5′-triphosphate (ATP) molecule isolated in an ion trap with (time-dependent) density functional theory calculations. Our study unravels the effect of protonation on the ATP structure and its spectral properties, providing structure–property relationships at atomistic resolution for protonated ATP (ATPH) isolated in the gas-phase conditions. On the other hand, the present C and N K-edge X-ray absorption spectra of isolated ATPH appear closely like those previously reported for solvated ATP at low pH. Therefore, the present work should be relevant for further investigation and modeling of structure–function properties of protonated adenine and ATP in complex biological environments.