Shuttle DNP spectrometer with a two-center magnet?

Physical Chemistry Chemical Physics Pub Date: 2010-05-11 DOI: 10.1039/C003381B

Abstract

A DNP set-up is described where a liquid sample is hyperpolarized by the electron-nucleus Overhauser effect in a field of 0.34 T and transferred to a field of 14.09 T for NMR detection. In contrast to a previous set-up, using two dedicated magnets for polarization and detection, a dedicated ferroshim system was inserted into the bore of a 14.09 T shielded cryomagnet to provide a homogeneous low-field region in the stray field above the magnetic center. After polarization in the low-field the sample is transferred to the high-field magnetic center within 40 ms by a pneumatic shuttle system. In our set-up a standard high-resolution inverse 1H/13C selective probe was used for NMR detection and a homebuilt EPR cavity, operating in the TM110 mode was used for polarisation. First experimental data are presented. We observed a maximum proton Overhauser enhancement of up to εHF = ?3.7 in the high-field position for a 5 mM 4-Oxo-TEMPO-D,15N (TEMPONE)/H2O sample. While this reproduces the DNP enhancement observed also in the old set-up, with the new set-up we observe enhancement on larger molecules that were impossible to enhance in the old set-up. Therefore, we can demonstrate for the first time Overhauser enhanced high resolution proton spectra of glucose and 2,2-dimethyl-2-silapentane-5-sulfonic acid sodium salt (DSS) in D2O, where the high resolution spectrum was acquired in the high-field position after polarizing the sample in the low-field.

Graphical abstract: Shuttle DNP spectrometer with a two-center magnet
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