3.1 Dynamics of Condensed Phase Molecular Systems

Hydrogen bonding of hydrated biomolecular and biomimetic systems is investigated with ultrafast vibrational spectroscopy. Hydration of biomolecules is addressed on the femto- to picosecond time scale by probing vibrational marker modes sensitive to molecular motions, energy exchange, and structural fluctuations of the hydration shell. Current activitities focus on hydration phenomena of phosphate units and of hydrated protons. Phosphate groups are crucial units in the sugar-phosphate backbone of DNA and RNA, and in the polar head groups of phospholipids. Hydrogen bond and hydration dynamics at the interface of these important biological systems with the aqueous environment can be monitored in a local manner through the vibrational marker modes of the phosphate group, i.e. the symmetric and asymmetric PO₂-stretching modes. Hydrated protons occur at crucial stages along proton transport pathways in transmembrane proton channel proteins. Structurally different hydrated proton species can be characterized through their specific vibrational marker modes and the associated mode couplings and dynamics. The aim with this combined experimental and theoretical approach to obtain a detailed characterization of microscopic mechanisms of electrical fields dictating the outcome of hydration and proton transport phenomena.