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Cross‐Polarization Electron‐Nuclear Double Resonance Spectroscopy
Author(s) -
Rizzato Roberto,
Bennati Marina
Publication year - 2015
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201500938
Subject(s) - ribonucleotide reductase , chemistry , electron nuclear double resonance , electron paramagnetic resonance , paramagnetism , spectroscopy , nuclear magnetic resonance , nuclear magnetic resonance spectroscopy , spins , electron , polarization (electrochemistry) , electron paramagnetic resonance spectroscopy , spectral line , molecular physics , protein subunit , physics , condensed matter physics , stereochemistry , biochemistry , quantum mechanics , gene , astronomy
Magnetic nuclei in the proximity of a paramagnetic center can be polarized through electron‐nuclear cross‐polarization and detected in electron‐nuclear double resonance (ENDOR) spectroscopy. This principle is demonstrated in a single‐crystal model sample as well as on a protein, the β2 subunit of E.coli ribonucleotide reductase (RNR), which contains an essential tyrosyl radical. ENDOR is a fundamental technique to detect magnetic nuclei coupled to paramagnetic centers. It is widely employed in biological and materials sciences. Despite its utility, its sensitivity in real samples is about one to two orders of magnitude lower than conventional electron paramagnetic resonance, thus restricting its application potential. Herein, we report the performance of a recently introduced concept to polarize nuclear spins and detect their ENDOR spectrum, which is based on electron‐nuclear cross polarization (eNCP). A single‐crystal study permits us to disentangle eNCP conditions and CP‐ENDOR intensities, providing the experimental foundation in agreement with the theoretical prediction. The CP‐ENDOR performance on a real protein sample is best demonstrated with the spectra of the essential tyrosyl radical in the β2 subunit of E.coli RNR.