Dr. Manfred Wagner
Manfred Wagner received his diploma in chemistry from the University of Mainz in 1988 in the group of Prof. K. Müllen and his PhD in 1993 at the MPI-P on the topic "Repetitive Diels-Alder reaction for the synthesis of ladder structures". From 1990 to 2002 he was co-responsible as a project leader for development of two- and three-dimensional carbonaceous materials (graphene-like as well as dendritic molecular structures). Also since 1990, he is accountable for the high-resolution NMR department of the Max Planck Institute for Polymer Research. His main topics besides studying the microstructure of macromolecules (e.g. polymers or biomolecules) are all kinds of active nuclei such as 1H, 7Li, 11B, 13C, 15N, 17O, 19F, 27Al, 29Si and 31P nuclei (and many other nuclei) and their physical and chemical properties/interactions over the last 33 years.
From Chemical Reactions towards Materials and their Properties: Studies of the MPIP NMR Core Facility
As a non-destructive characterization method that allows in-situ measurements, NMR spectroscopy has become a method of central importance to physicists, chemists, and biologists over the past 63 years. NMR spectroscopy is indispensable for the complete structural characterization of new organic molecules as well as for tracking their reaction kinetics (e.g., polymerizations) by in situ NMR measurements. For inorganic complexes, for example, optimized NMR experiments allow us to understand their molecular structure and measure their electronic properties. Furthermore, it is also possible to determine the three-dimensional structure of biological macromolecules, e.g., proteins, protein fragments, or DNA derivatives, under both natural and specifically controlled conditions (pH, water, salts, etc.). As another example of cross-phase NMR studies offered by the NMR method, the analysis of sol-gel reactions at water/oil interfaces allows the hydrolysis and indirectly the condensation of different silane species to be followed quantitatively as a function of time by high-resolution 1H NMR spectroscopy in situ. In addition, hetero-core NMR experiments are also used to understand either the internal structure of silicate particles, with 29Si solution NMR or 29Si solid-state (MAS) NMR. Here the broadness of the NMR method comes into play, being able to measure over different phases (solid, gel, liquid).
Key Achievements: Understanding of nucleus interactions in several phases, structure/material properties, new approaches to quantify systems.
Unraveling the self-assembly, aggregation, gelation and fibrillation of peptides/nucleotides
NMR studies allow a wide variety of experiments to understand, for example, the temperature-dependent self-assembly kinetics of biologically inspired peptide-based systems. These materials typically appear as assembled structures at ambient temperature. Due to the short T2 times of the assembled states good spectral resolution of the NMR signals cannot be achieved. However, with increasing the temperature, the assembly process is destabilized and dissociation processes increase the local molecular mobility so that individual monomer signals become observable. Especially for kinetic measurements, the measurement time to achieve a signal-to-noise ratio sufficient for quantitative analysis is a major limitation.
In the future, we try to quantify the different structures inside the complex mixtures depending on temperature, time, pH and other parameters.
Key Achievements: Understanding the initiation of the self-assembling system, reduced mobility and NMR signals, correlation of changes in T, pH, c, t and other.
2.2 Macromolecules, Proteins, and Active Agents
NMR techniques provide insights into biochemical processes, also in complex molecular environments. Due to the presence of many protic compounds, 1H NMR spectroscopy alone cannot provide the required information of the chemical reactions and isotopic enrichment (e.g. 13C- or 15N-labeled amino acids or sugars) of targeted molecules is often required. Under these conditions, fluorine is an "ideal" labeling nucleus for studying reactions in complex and/or living systems. Organic fluorides are present only in very small amounts in living organisms, which enables recording almost background free 19F-NMR spectra, which offers many opportunities, because
- C-F bonds are inert under physiological conditions
- Fluorine has a small atomic radius
- 19F is the second most sensitive, non-radioactive nucleus in NMR spectroscopy
- Fluorine occurs in nature isotopically pure in the NMR active form (19F).
- 19F has a remarkably broad chemical shift range (-300 to 50 ppm), promising a high sensitivity to small changes in the chemical environment around the label.
The heteronuclear Overhauser spectroscopy (1H-19F HOESY, transfer of nuclear spin polarization from one population of spin-active nuclei to another via cross-relaxation) or direct through bond correlation methods (2D 1H-19F COSY ), allows using fluorine atoms as a sensitive "antenna" to monitor changes in a complex chemical environment, which will be important for several new projects in the groups of Katharina Landfester and Tanja Weil.
In the future, we plan to extend the 1H-19F methods to STD-NMR (saturation transfer difference NMR spectroscopy) approaches to elucidate possible drug/small molecule interactions with larger structures such as proteins or other macromolecules, and modify and develop them to alter cellular functions.
Key Achievements: 19F-Sensor in proteins, saturation experiments in the fluorine frequency range to understand interactions.