Hydrogen bonds, as weak chemical bonds, are one of the fundamental interactions in nature. On the one hand, they determine the structure of biological molecules, such as deoxyribonucleic acid (DNA), the carrier of the genetic information in the cell. On the other hand, due to their low bond strength, hydrogen bonds undergo fluctuations which, for example in water, lead to extremely rapid changes in the arrangement of the water molecules. In doing so, hydrogen bonds are repeatedly broken and reshaped. Despite intensive research, the structural dynamics of hydrogen bonds, which essentially take place in the femtosecond range (1 femtosecond = 10-15 s = 1 millionth of a billionth of a second), is only beginning to be known.
The award-winning project uses novel methods of ultra-short-time optics from the infrared to the X-ray range for the investigation of hydrogen bonds. The goal is the determination of molecular structures in real time, i. Molecular processes are triggered and tracked with ultrashort light pulses. With X-ray pulses whose wavelength corresponds approximately to the length of a chemical bond, a sequence of "snapshots" of the molecular structures can be taken directly. Infrared pulses provide insight into local motions and couplings of molecular groups. The experiments investigate the interaction of DNA molecules with their aqueous environment, i. the coupling of water molecules to different units of the DNA double helical structure, the fluctuations of the water envelope around the DNA, and the role of water in the redistribution and transport of energy from the DNA into its environment. Since hydrogen bonds play an important role in almost all biochemical reactions, the results are of universal importance. In another part of the project, hydrogen-bonded molecular crystals are used to determine structures that result from the redistribution of charges and the transport of protons. These elementary chemical processes are crucial for the electrical properties of crystals, which have potential for use as ferroelectrics in novel electronic devices.
