Magnesium contact ions stabilize the macromolecular structure of transfer RNA [DOI: 10.1021/acs.jpcb.0c08966]: We have identified contact pairs of positively charged magnesium ions and negatively charged phosphate groups as a decisive structural element for minimizing the electrostatic energy of tRNA and, thus, stabilizing its tertiary structure. The results give detailed insight in the electric properties of a key biomolecule and underscore the relevance of molecular probes for elucidating the relevant molecular interactions.
Quantum state mixing in photobiology [DOI: 10.1073/pnas.2319676121]: The excited state character governing the reaction dynamics of the protonated Schiff base in bacteriorhodopsin, a light induced proton pump, has remained controversial. We could show that nonadiabatic mixing of S1 and S2 excited states and temporal averaging over the first 120 fs of the ultrafast excited state dynamics account for the measured dipole changes in THz Stark spectroscopy. On the timescale of the experiment, the protein environment of the chromophore is practically frozen, providing a clear view on its electronic properties and revealing a quantum mixing of states as a key mechanism in molecular systems relevant for chemistry and biology.
Magnesium ions slow down water dynamics on short length scales [DOI: 10.1021/acsphyschemau.2c00034]: Liquid water, the native medium for biochemical processes, responds to the presence of charged ions by changing its local structure. The influence of ions on water is usually classified via the Hofmeister series which ranks ions based on their ability to structure the water around them. We could demonstrate a significantly more complex influence of ions on the dynamics of surrounding water molecules. The presence of Mg2+ ions reduces the ultrafast fluctuations of the water shell around a sulfate ion, leading to a specific slowdown in the solvation dynamics of hydrated MgSO4. Contrary to the widespread account in the literature, the described effects are of short range and limited to the first 1-2 water layers around the sulfate ion.
Terahertz waves from electrons oscillating in liquid water [DOI: 10.1103/physrevlett.126.097401]: Electrons in water are a prototypical quantum system in interaction with a fluctuating environment. Their non-equilibrium generation leads to long-lived oscillatory dynamics in the terahertz range with a oscillation frequency determined by the local electric field the liquid environment. Surprising is the comparably weak damping of the oscillations which points to a weak interaction with the fluctuating environment. The results suggest a polaron picture of solvated electrons, i.e. a quasi-particle of coupled motions of the electron and the surrounding water shell.
