The Department of Biological Chemistry invites to a guest lecture by Dr. Guinevere Mathies (Emmy Noether Group Leader), Department of Chemistry, University of Konstanz.

Title: Pushing the envelope of solid-state NMR: from revealing crystallization pathways to improving sensitivity with microwave pulse sequences

Abstract:

When it comes to answering tough structural questions about chemical systems in the solid state, NMR spectroscopy is hard to beat. Magic-angle spinning (MAS) and high magnetic fields (nowadays up to 28 T) assure good resolution and an extensive library of radiowave pulse sequences makes it possible to observe inter-nuclear distances, local chemical properties, and motion.

In the first part of the seminar, I will describe a case in point: our recent investigation of amorphous calcium carbonate (ACC), an intermediate in biomineralization.[1] With the help of MAS NMR, we could determine that a network of mobile water molecules pervades the bulk of ACC nanoparticles, which itself consists of rigid calcium carbonate with embedded structural water molecules. This nanoscale structure is a remainder of the history of ACC as the suspended phase of a colloid and consistent with the pre-nucleation cluster pathway.

Insufficient sensitivity is the bottle neck in many applications of MAS NMR. In the study of complex materials and their formation pathways, for example, rare or transient species often remain undetected. While dynamic nuclear polarization (DNP) has proven to be a suitable remedy, current MAS DNP methods are not very sophisticated. They all rely on continuous high-power microwave irradiation, which is neither an efficient nor a flexible way of inducing electron-nuclear polarization transfer. If one were to use a microwave pulse sequence instead, the polarization transfer can be better controlled, optimized, and tailored to the task at hand. In the second part of this seminar, I will tell you about our first careful steps in the development of pulsed DNP.[2,3]

1. Gindele et al. Nat. Commun. 15:80 (2024) 2. Redrouthu et al. J. Chem. Phys. 159, 014201 (2023) 3. Redrouthu and Mathies J. Am. Chem. Soc. 144, 1513-1516 (2022)