Speaker
Description
Intermolecular Coulombic decay (ICD) is a non-local autoionization process that has the potential to selectively probe the first hydration shell of solvated molecules. Here, we demonstrate the applicability of ICD spectroscopy to biomolecules in a complex environment. Firstly, we access site-specific information on the interaction of adenosine triphosphate in the aqueous phase (ATP(aq)) with magnesium ions (Mg2+(aq)). Because ICD is sensitive to the immediate environment of the target, information about such interactions is conveyed by the emerging ICD electrons following the ionization of core-level Mg 1s orbitals. A recently observed variant of ICD that follows resonant X-ray excitation of the target has an increased sensitivity to the chemical composition of the solvation shell and enables the determination of the absolute binding energies of the solvating molecules, for the first time. In a second example, we extend the resonant ICD to investigate the intermolecular interactions of aqueous-phase proline with Ca2+ ions. We provide evidence of ion pairing between the Ca2+ ions and the carboxylic acid moiety of proline replacing the water molecules in the ions's coordination shell. Therefore, we establish ICD spectroscopy as a new and powerful tool for biomolecular structure investigations.
