| Heisenberg spin exchange effects of nitroxide radicals on Overhauser dynamic nuclear polarization in the low field limit at 1.5mT. | |
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MedLine Citation:
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PMID: 20188611 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) at very low magnetic fields (0.05-20mT) have gained interest due to the simple and portable magnet design and newly emerging applications outside of the usual laboratory setting. A method to enhance the NMR signal is needed due to the low thermal polarization of nuclear spins at these fields; dynamic nuclear polarization (DNP) via the Overhauser effect from free radicals is an attractive option. In this report we describe a DNP-enhanced NMR system operating at a fixed field of 1.5mT and measure (1)H signal enhancements of up to -350 fold during the saturation of a selected electron spin resonance (ESR) transition of dissolved nitroxide radicals. This -350 fold enhanced polarization is equivalent to what would be obtained by prepolarization in a 0.53T field. The ESR spectra at varying radical concentrations are indirectly found through DNP-enhanced NMR detection. Here, ESR line broadening at higher radical concentrations due to Heisenberg electron spin exchange is observed. Enhancements in the limit of maximum power are reported as a function of concentration for three ESR transitions, and are found to increase with concentration. The >300 fold (1)H NMR signal amplifications achievable at 1.5mT will reduce experimental time by several orders of magnitude, permitting NMR relaxation, imaging or pulsed-field gradient diffusion experiments that are inaccessible without using the DNP effect at 1.5mT. We demonstrate the potential benefit of such large signal amplification schemes through T(1) and T(2) relaxation measurements carried out in a much shorter time when employing DNP. Finally, we compare our results to those obtained in the earth's magnetic field and find that the signal to noise ratio (SNR) of DNP-enhanced signal at 1.5mT is much greater than that obtained by previous studies utilizing DNP enhancement in the 0.05mT earth's magnetic field. |
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Authors:
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Mark D Lingwood; Ivan A Ivanov; Alissa R Cote; Songi Han |
Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S. Date: 2010-02-06 |
Journal Detail:
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Title: Journal of magnetic resonance (San Diego, Calif. : 1997) Volume: 204 ISSN: 1096-0856 ISO Abbreviation: J. Magn. Reson. Publication Date: 2010 May |
Date Detail:
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Created Date: 2010-04-05 Completed Date: 2010-07-16 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 9707935 Medline TA: J Magn Reson Country: United States |
Other Details:
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Languages: eng Pagination: 56-63 Citation Subset: IM |
Copyright Information:
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Copyright 2010 Elsevier Inc. All rights reserved. |
Affiliation:
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Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, CA 93106-9510, USA. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Computer Simulation Magnetic Resonance Spectroscopy / methods* Models, Chemical* Nitrogen Oxides / analysis, chemistry* Protons* Sensitivity and Specificity Spin Labels |
| Chemical | |
Reg. No./Substance:
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0/Nitrogen Oxides; 0/Protons; 0/Spin Labels; 14332-28-6/nitroxyl |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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