Dynamic Nuclear Polarization for Sensitivity Enhancement in Biomolecular Solid-State NMR

Abstract

Solid-state NMR with magic-angle spinning (MAS) is an important method in structural biology. While NMR can provide invaluable information about local geometry on an atomic scale even for large biomolecular assemblies lacking long-range order, it is often limited by low sensitivity due to small nuclear spin polarization in thermal equilibrium. Dynamic nuclear polarization (DNP) has evolved during the last decades to become a powerful method capable of increasing this sensitivity by two to three orders of magnitude, thereby reducing the valuable experimental time from weeks or months to just hours or days; in many cases, this allows experiments that would be otherwise completely unfeasible. In this review, we give an overview of the developments that have opened the field for DNP-enhanced biomolecular solid-state NMR including state-of-the-art applications at fast MAS and high magnetic field. We present DNP mechanisms, polarizing agents, and sample constitution methods suitable for biomolecules. A wide field of biomolecular NMR applications is covered including membrane proteins, amyloid fibrils, large biomolecular assemblies, and biomaterials. Finally, we present perspectives and recent developments that may shape the field of biomolecular DNP in the future.

In-Cell Structural Biology by NMR: The Benefits of the Atomic Scale

“…[67][68][69] In-cell ssNMR is somehow in its infancy and will certainly be fueled by 1 H-detection and Dynamic-Nuclear Polarization (DNP) in the coming years. [70][71][72][73] Describing the methods associated to in-cell ssNMR would thus be a more prospective exercise. Importantly, ssNMR is limited to the characterization of frozen cells: it ensures cellular integrity during ssNMR measurements, which require fast Magic-Angle Spinning (MAS, about 10 to 100 kHz) to obtain atomic-scale information on macromolecules.…”

“…We decided to limit ourselves to solution-NMR approaches. Solid-state NMR (ssNMR) provided interesting structural descriptions using native membranes, e.g., on the interfering modes of antibiotics in bacterial membranes, − or on the structure of prokaryotic and eukaryotic membrane proteins. − In-cell ssNMR is somehow in its infancy and will certainly be fueled by 1 H-detection and dynamic nuclear polarization (DNP) in the coming years. − Describing the methods associated with in-cell ssNMR would thus be a more prospective exercise. Importantly, ssNMR is limited to the characterization of frozen cells: It ensures cellular integrity during ssNMR measurements, which require fast magic-angle spinning (MAS, about 10–100 kHz) to obtain atomic-scale information on macromolecules.…”

Biomolecular and Biological Applications of Solid-State NMR with Dynamic Nuclear Polarization Enhancement

“…As the focus of this review is on the biological applications of DNP-enhanced ssNMR, section 2 does not aim to provide a comprehensive coverage of DNP methodology. Rather, we focus on what might be of interest to typical biomolecular NMR spectroscopists when considering whether and how to apply MAS-DNP to their systems of interest, leaving DNP theoretical background, hardware, and methodology developments to other excellent reviews on these topics in this special issue 22 and elsewhere. 4,23 While the specific topic of oriented membrane applications are briefly covered in section 2.9, the bulk of this review is concerned with MAS-DNP.…”

PyrroTriPol: a Semi-rigid Trityl-Nitroxide for High Field Dynamic Nuclear Polarization

“…2,[4][5][6][7][8] Polarization transfer results in substantial increase in sensitivity, e.g. with a theoretical enhancement of 1 H ̴ 660 and 13 C ̴ 2600, enabling new insights into structure and function in biology [9][10][11][12][13][14][15][16] and materials. [3][4][5][17][18][19][20] Several DNP mechanisms have been proven to be active under MAS at high magnetic field (> 5 T), namely the solid effect (SE), the Overhauser effect (OE) and the cross effect (CE).…”