We report our recent efforts directed at improving high-field dynamic nuclear polarization (DNP) experiments. We investigated a series of thiourea nitroxide radicals and the associated DNP enhancements ranging from epsilon=25 to 82, which demonstrate the impact of molecular structure on performance. We directly polarized low-gamma nuclei, including C-13, H-2, and O-17, by the cross effect mechanism using trityl radicals as a polarization agent. We discuss a variety of sample preparation techniques for DNP with emphasis on the benefits of methods that do not use a glass-forming cryoprotecting matrix. Lastly, we describe a corrugated waveguide for use in a 700MHz/460GHz DNP system that improves microwave delivery and increases enhancements up to 50%.
Topical Developments in High-Field Dynamic Nuclear Polarization / Vladimir K. Michaelis; Ta-Chung Ong; Matthew K. Kiesewetter; Derik K. Frantz; Joseph J. Walish; Enrico Ravera; Claudio Luchinat; Timothy M. Swager; Robert G. Griffin. - In: ISRAEL JOURNAL OF CHEMISTRY. - ISSN 0021-2148. - STAMPA. - 54:(2014), pp. 207-221. [10.1002/ijch.201300126]
Topical Developments in High-Field Dynamic Nuclear Polarization
RAVERA, ENRICO;LUCHINAT, CLAUDIO;
2014
Abstract
We report our recent efforts directed at improving high-field dynamic nuclear polarization (DNP) experiments. We investigated a series of thiourea nitroxide radicals and the associated DNP enhancements ranging from epsilon=25 to 82, which demonstrate the impact of molecular structure on performance. We directly polarized low-gamma nuclei, including C-13, H-2, and O-17, by the cross effect mechanism using trityl radicals as a polarization agent. We discuss a variety of sample preparation techniques for DNP with emphasis on the benefits of methods that do not use a glass-forming cryoprotecting matrix. Lastly, we describe a corrugated waveguide for use in a 700MHz/460GHz DNP system that improves microwave delivery and increases enhancements up to 50%.I documenti in FLORE sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.