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Research

In the following, a brief summary of our current research activities is given. For more details, please have a look at our publications.

Targets

Figure 1: Structure of a [NiFe] hydrogenase.

Figure 1: Structure of a [NiFe] hydrogenase.

Figure 2: Active-site structure, IR absorption spectrum, and ligand vibrations of a [NiFe] hydrogenase.

Figure 2: Active-site structure, IR absorption spectrum, and ligand vibrations of a [NiFe] hydrogenase.

Our research focusses on bioinorganic catalysts, i.e. metalloenzymes and related bio-inspired transition metal systems. In particular, we are interested in hydrogenases – complex and phylogenetically old multi-subunit enzymes that contain several metal cofactors (see Figure 1). These biological macromolecules catalyze the reversible cleavage of molecular hydrogen (H2) into protons and electrons, typically at sophisticated bimetallic active sites (see Figure 2).

On the one hand, H2 is an ideally clean fuel that releases large amounts of energy but no greenhouse gasses upon combustion. On the other hand, the H–H bond is remarkably strong and completely nonpolar, which makes H2 activation and cleavage a formidable task. Thus, hydrogenases represent valuable biocatalysts that are relevant for both fundamental and applied catalysis research. In this respect, they can serve as key players in diverse biotechnological applications and as blueprints for the bioinspired design of synthetic H2-converting catalysts. Relying on a complex interplay between multiple metal sites and the protein as well as both chemical and non-chemical reaction steps, hydrogenases are also valuable model systems to understand – on a fundamental level – how metalloenzymes catalyze demanding reactions and how they differ from synthetic analogues.

Methodology

Figure 3: Nonlinear IR spectroscopy of [NiFe] hydrogenases. (A) Bond properties und energy dissipation. (B) Ultrafast equilibrium dynamics and coherent phenomena. (C) Energy exchange and vibrational coupling (2D-IR).

Figure 3: Nonlinear IR spectroscopy of [NiFe] hydrogenases. (A) Bond properties und energy dissipation. (B) Ultrafast equilibrium dynamics and coherent phenomena. (C) Energy exchange and vibrational coupling (2D-IR).

To reveal how the remarkable functional features of hydrogenases and other metalloenzymes are determined by their structure, we use an integrated approach of advanced spectroscopic and theoretical methods. In general, we aim to measure what can be measured and use computational tools to calculate especially those properties that are hard or impossible to access experimentally. We also combine these two strategies to facilitate the understanding of experimental data by simulations.

Special emphasis is placed on spectroscopic techniques that probe molecular vibrations, especially advanced infrared (IR) spectroscopy. Molecular vibrations are inherently linked to the atomic composition and connectivity of a chemical compound. Thus, vibrational spectroscopic techniques provide detailed insights into the electronic structure and nuclear configuration of various molecular systems.

In contrast to many other experimental tools, IR spectroscopy can obtain this information in a nondestructive manner under biologically relevant or operando conditions. Due to the presence of diatomic ligands with highly localized, energy-separated, and structurally sensitive bond stretch vibrations, this technique is also particularly suited for the characterization of hydrogenases (see Figure 2). While conventional IR absorption spectroscopy has been applied to these enzymes for decades, we have only recently introduced ultrafast and two-dimensional (2D) IR techniques as new tools in hydrogenase research. Inter alia, these nonlinear techniques yield detailed de novo insights into bonding properties, intramolecular interactions, and ultrafast equilibrium dynamics (see Figure 3).

Objectives

Current research follows a threefold approach. First, we aim to integrate nonlinear IR techniques and our newly established strategies into ongoing research on hydrogenases, thereby addressing pending questions on structure, function, and dynamics. Moreover, we plan to adapt this methodology for exploring further metalloenzymes and other catalytic systems of interest. Finally, we strive to expand our experimental and theoretical approach in order obtain a complete picture of reaction and equilibrium dynamics in metalloenzyme catalysis as well as a proper understanding of all probed observables. If you are interested in working with us on these topics – as a student, colleague, or collaboration partner – don’t hesitate to contact us.

Keywords

  • 2D-IR Spectroscopy
  • Bioinorganic Catalysis
  • Experimental and Theoretical Biophysics
  • Hydrogen
  • Hydrogenases
  • Infrared Spectroscopy
  • IR Spectroscopy
  • Metalloenzymes
  • Multidimensional Spectroscopy
  • Ultrafast Dynamics in Catalysis
  • Ultrafast Spectroscopy
  • Vibrational Spectroscopy