Pulse Electron Double Resonance Detected Multinuclear NMR Spectra of Distant and Low Sensitivity Nuclei and Its Application to the Structure of Mn(II) Centers in Organisms

• Published in: The journal of physical chemistry. B Vol. 119; no. 43; pp. 13515 - 13523
• Main Authors: Bruch, Eduardo M, Warner, Melissa T, Thomine, Sébastien, Tabares, Leandro C, Un, Sun
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 29.10.2015
• Subjects: Deinococcus - chemistry; Deinococcus - cytology; Electron Spin Resonance Spectroscopy; Escherichia coli - chemistry; Escherichia coli - cytology; Life Sciences; Manganese - chemistry; Models, Molecular; Molecular Structure; Nuclear Magnetic Resonance, Biomolecular; Organometallic Compounds - chemistry; Quantum Theory
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/acs.jpcb.5b01624

The ability to characterize the structure of metal centers beyond their primary ligands is important to understanding their chemistry. High-magnetic-field pulsed electron double resonance detected NMR (ELDOR-NMR) is shown to be a very sensitive approach to measuring the multinuclear NMR spectra of the nuclei surrounding Mn­(II) ions. Resolved spectra of intact organisms with resonances arising from 55Mn, 31P, 1H, 39K, 35Cl, 23Na, and 14N nuclei surrounding Mn2+ centers were obtained. Naturally abundant cellular 13C could be routinely measured as well. The amplitudes of the 14N and 2H ELDOR-NMR spectra were found to be linearly dependent on the number of nuclei in the ligand sphere. The evolution of the Mn­(II) ELDOR-NMR spectra as a function of excitation time was found to be best described by a saturation phenomenon rather than a coherently driven process. Mn­(II) ELDOR-NMR revealed details about not only the immediate ligands to the Mn­(II) ions but also more distant nuclei, providing a view of their extended structures. This will be important for understanding the speciation and chemistry of the manganese complexes as well as other metals found in organisms.