Rostock 2019 – scientific programme

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MO: Fachverband Molekülphysik

MO 14: Ultrafast Multidimensional and Control Approaches

MO 14.1: Talk

Wednesday, March 13, 2019, 14:00–14:15, S HS 001 Biologie

Probing Phosphate-Magnesium Ion Interactions in Water using Ultrafast 2D-IR spectroscopy — •Jakob Schauss, Fabian Dahms, Benjamin P. Fingerhut, and Thomas Elsaesser — Max Born Institute for Nonlinear Optics and Short-Pulse Spectroscopy, Berlin, Germany

Biomolecules are fundamentally affected by electric interactions with their surrounding solvent shell and the embedded ions. Mg²⁺-ions are known to play a vital role in stabilizing RNA geometries, yet the underlying interactions are mainly unresolved. To unravel microscopic couplings and dynamics, non-invasive molecular probes are required, such as the phosphate vibrations of the nucleic acid backbone.

We used femtosecond 2D-IR spectroscopy on the dimethylphosphate anion DMP⁻, an established model system of the DNA/RNA backbone, and were able to observe a distinct blue shift of the asymmetric stretch vibration ν_as(PO₂)⁻ when magnesium ions were added. Concomitant theoretical ab-initio simulations attribute this frequency shift to the formation of contact DMP⁻/Mg²⁺ ion pairs, providing a handle to distinguish site-bound and diffuse ions in biomolecular systems in future research.