How Does Mg${}_{(aq)}^{2+}$ Interact with ATP${}_{(aq)}$? Biomolecular Structure through the Lens of Liquid-Jet Photoelectron Spectroscopy

Abstract

Site-specific information on how adenosine triphosphate in the aqueous phase (ATP${}_{(aq)}$) interacts with magnesium (Mg${}_{(aq)}^{2+}$) is a prerequisite to understanding its complex biochemistry. To gather such information, we apply liquid-jet photoelectron spectroscopy (LJ-PES) assisted by electronic-structure calculations to study ATP${}_{(aq)}$ solutions with and without dissolved Mg${}^{2+}$. Valence photoemission data reveal spectral changes in the phosphate and adenine features of ATP${}_{(aq)}$ due to interactions with the divalent cation. Chemical shifts in Mg 2p, Mg 2s, P 2p, and P 2s core-level spectra as a function of the Mg${}^{2+}$/ATP concentration ratio are correlated to the formation of [MgATP]${}_{(aq)}^{-2}$ and Mg${}_2$ATP${}_{(aq)}$ complexes, demonstrating the element-sensitivity of the technique to Mg${}^{2+}$-phosphate interactions. In addition, we report and compare P 2s data from ATP${}_{(aq)}$ and adenosine mono- and di-phosphate (AMP${}_{(aq)}$ and ADP${}_{(aq)}$, respectively) solutions, probing the electronic structure of the phosphate chain and the local environment of individual phosphate units in ATP${}_{(aq)}$. Finally, we have recorded intermolecular Coulombic decay (ICD) spectra initiated by ionization of Mg 1s electrons to probe ligand exchange in the Mg${}^{2+}$-ATP${}_{(aq)}$ coordination environment, demonstrating the unique capabilities of ICD for revealing structural information. Our results provide an overview of the electronic structure of ATP${}_{(aq)}$ and Mg${}^{2+}$-ATP${}_{(aq)}$ moieties relevant to phosphorylation and dephosphorylation reactions that are central to bioenergetics in living organisms.

Main manuscript: 16 pages, 8 figures. Supporting information: 31 pages, 7 figures

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Cited by in corpus (1)

• Intermolecular Radiative Decay: A non-local decay mechanism providing an insider's view of the solvation shell