Heteronuclear Cross‐Relaxation Effects in the NMR Spectroscopy of Hyperpolarized Targets |
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Authors: | Dr Kevin J Donovan Dr Adonis Lupulescu Prof Dr Lucio Frydman |
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Affiliation: | Chemical Physics Department, Weizmann Institute of Science, Rehovot (Israel), Fax: (+972)?8‐934‐4903 |
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Abstract: | Dissolution dynamic nuclear polarization (DNP) enables high‐sensitivity solution‐phase NMR experiments on long‐lived nuclear spin species such as 15N and 13C. This report explores certain features arising in solution‐state 1H NMR upon polarizing low‐γ nuclear species. Following solid‐state hyperpolarization of both 13C and 1H, solution‐phase 1H NMR experiments on dissolved samples revealed transient effects, whereby peaks arising from protons bonded to the naturally occurring 13C nuclei appeared larger than the typically dominant 12C‐bonded 1H resonances. This enhancement of the satellite peaks was examined in detail with respect to a variety of mechanisms that could potentially explain this observation. Both two‐ and three‐spin phenomena active in the solid state could lead to this kind of effect; still, experimental observations revealed that the enhancement originates from 13C→1H polarization‐transfer processes active in the liquid state. Kinetic equations based on modified heteronuclear cross‐relaxation models were examined, and found to well describe the distinct patterns of growth and decay shown by the 13C‐bound 1H NMR satellite resonances. The dynamics of these novel cross‐relaxation phenomena were determined, and their potential usefulness as tools for investigating hyperpolarized ensembles and for obtaining enhanced‐sensitivity 1H NMR traces was explored. |
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Keywords: | hyperpolarization NMR spectroscopy nuclear hyperpolarization polarization transfer satellite‐peak enhancement |
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