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13 C dynamic nuclear polarization using isotopically enriched 4-oxo-TEMPO free radicals

13 C dynamic nuclear polarization using isotopically enriched 4-oxo-TEMPO free radicals

Peter Niedbalski, Christopher Parish, Andhika Kiswandhi, Lloyd Lumata

Magn Reson Chem. 2016 Dec;54(12):962-967.

PMID: 27377643

Abstract:

The nitroxide-based free radical 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) is a widely used polarizing agent in NMR signal amplification via dissolution dynamic nuclear polarization (DNP). In this study, we have thoroughly investigated the effects of 15 N and/or 2 H isotopic labeling of 4-oxo-TEMPO free radical on 13 C DNP of 3 M [1-13 C] sodium acetate samples in 1 : 1 v/v glycerol : water at 3.35 T and 1.2 K. Four variants of this free radical were used for 13 C DNP: 4-oxo-TEMPO, 4-oxo-TEMPO-15 N, 4-oxo-TEMPO-d16 and 4-oxo-TEMPO-15 N,d16 . Our results indicate that, despite the striking differences seen in the electron spin resonance (ESR) spectral features, the 13 C DNP efficiency of these 15 N and/or 2 H-enriched 4-oxo-TEMPO free radicals are relatively the same compared with 13 C DNP performance of the regular 4-oxo-TEMPO. Furthermore, when fully deuterated glassing solvents were used, the 13 C DNP signals of these samples all doubled in the same manner, and the 13 C polarization buildup was faster by a factor of 2 for all samples. The data here suggest that the hyperfine coupling contributions of these isotopically enriched 4-oxo-TEMPO free radicals have negligible effects on the 13 C DNP efficiency at 3.35 T and 1.2 K. These results are discussed in light of the spin temperature model of DNP. Copyright © 2016 John Wiley & Sons, Ltd.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP2896700	4-Oxo-TEMPO		2896-70-0	Price

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