Universität Bonn

Physical and Theoretical Chemistry


Cognitive adventures of single neurons
May 27, 2024 from 05:00 PM to 06:00 PM

The human medial temporal lobe contains neurons that respond selectively to the semantic contents of a presented stimulus. These "concept cells" may respond to very different pictures of a given person and even to their written and spoken name. Their response latency is far longer than necessary for object recognition, they follow subjective, conscious perception, and they are found in brain regions that are crucial for declarative memory formation. It has thus been hypothesized that they may represent the semantic "building blocks" of episodic memories. In this talk I will present data from single unit recordings in the hippocampus, entorhinal cortex, parahippocampal cortex, and amygdala during paradigms involving object recognition as well as encoding and consolidation of episodic memories in order to characterize the role of concept cells in these cognitive functions.

NMR spectroscopy: more light – more signal
Jun 10, 2024 from 12:00 PM to 01:00 PM

The methods of magnetic resonance (NMR, EPR and MRI) offer fantastic analytical and diagnostic possibilities. As the radiation used is of very low energy, these methods also have the advantage of being non-invasive. Unfortunately, the low energy is also associated with low sensitivity, which means that sample volumes in NMR have to be quite large and measurement times in MRI quite long. So- called hyperpolarization techniques offer one way of increasing sensitivity. The best known is called "dynamic nuclear polarization" (DNP) and uses electron spins to "pump" nuclear spins. To do this, the sample must be irradiated with microwaves. Of course, one would prefer to "pump" with light. This is possible with the help of "photo-CIDNP" (photochemically induced dynamic nuclear polarization). The lecture will explain the origin, applications and possibilities of photo-CIDNP NMR.

Mechanistic insights from unpaired electrons
Jul 08, 2024 from 05:00 PM to 06:00 PM

Dr. Rössler’s lab makes use of chemical principles to understand fundamentally important reactions in biology. Reduction-oxidation (redox) reactions underpin innumerable chemical reactions and much of the chemistry of life. Many redox reactions proceed via radical intermediates and these are often located in mechanistically key locations. She investigates how oxidation-state changes govern respiration in the respiratory complex I and photosynthesis in photosynthetic complex I and how nature has fine-tuned the redox properties of its many intricate molecular machines. Membranes play a fundamentally important role for many proteins and she is investigating the role of membranes on protein activity and function through spin labels and protein-intrinsic paramagnetic centres.

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