Kolloquium

Kolloquium

Am Donnerstag, 14.12.2017, 13:00 Uhr
im Seminarraum 101, Fak. f. Chemie u. Mineralogie, Johannisallee 29

spricht Herr Dr. Björn Corzilius, Biomolekulares Magnetresonanz-Zentrum (BMRZ), Johann-Wolfgang-Goethe-Universität Frankfurt

zum Thema: ″Dynamic nuclear polarization for sensitivity-enhancement of solid-state NMR″

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NMR is a powerful and indispensable technique in structural biology. Magic-angle spinning (MAS) NMR has proven extremely valuable for the determination of atomistic structures in structural biology as well as materials science. Nevertheless, the inherently low sensitivity towards nuclear spins is still one of the limiting factors in its application. Dynamic nuclear polarization (DNP) has been introduced as a tool to overcome this problem by transferring the significantly larger spin polarization of unpaired electrons to the nuclei of interest during a typical NMR experiment. This allows the investigation of a wide range of sample systems and scientific problems where the analyte is in too low concentration to be amenable to standard MAS NMR techniques, for example in complex host-guest systems or surface-active materials, or where isotope labeling is impossible.[1] For DNP, electron spins have to be present as polarizing agents. This can be achieved by adding paramagnetic species to the (diamagnetic) sample. Besides the typical nitroxide-based persistent radicals, paramagnetic metal complexes of Mn(II), Gd(III), and Cr(III) are of particular interest due to their electron paramagnetic resonance (EPR) spectral properties and possibility to be incorporated within biomolecules or materials.[2-5]
In the presentation, it will be shown that endogenous paramagnetic ions can be used for intramolecular DNP. Several examples of paramagnetic biomolecules are presented, including proteins and ribonucleic acids and the successful polarization transfer between the paramagnetic moiety and the nuclei of interest is demonstrated.[6, 7] A similar approach is shown by doping a diamagnetic host lattice of a material with a paramagnetic dopant. These results will be complemented by examples utilizing a more conventional approach where exogenous polarizing agents are added to the sample. The prospect of site-specific, direct nuclear polarization by endogenous paramagnetic sites which can be used for the generation of distance constraints in structural biology and materials science will be discussed, and heteronuclear cross-relaxation under MAS DNP will be introduced as a novel tool for the selective probing of molecular contact surfaces.[8]

[1] A.S. Lilly Thankamony et al., Prog. Nucl. Magn. Reson. Spectrosc., 102-103 (2017) 120-195.
[2] B. Corzilius et al., J. Am. Chem. Soc., 133 (2011) 5648-5651.
[3] B. Corzilius, Phys. Chem. Chem. Phys., 18 (2016) 27190-27204.
[4] M. Kaushik et al., Angew Chem Int Ed Engl, 56 (2017) 4295-4299.
[5] B. Corzilius et al., J. Am. Chem. Soc., 136 (2014) 11716-11727.
[6] P. Wenk et al., J. Biomol. NMR, 63 (2015) 97-109.
[7] M. Kaushik et al., Phys. Chem. Chem. Phys., 18 (2016) 27205-27218.

 

 

letzte Änderung: 27.11.2017