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Communication

PASADENA Hyperpolarization of Succinic Acid for MRI and NMR Spectroscopy

Eduard Y. Chekmenev,^†^‡ Jan Hövener,^‡ Valerie A. Norton,^† Kent Harris,^‡ Lynne S. Batchelder,^§ Pratip Bhattacharya,^‡ Brian D. Ross,^‡ and Daniel P. Weitekamp*^†

A. A. Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, California 91125, Enhanced MR Laboratory, Huntington Medical Research Institutes, Pasadena, California 91105, and Cambridge Isotope Laboratories, Andover, Massachusetts 01810

J. Am. Chem. Soc., 2008, 130 (13), pp 4212–4213

DOI: 10.1021/ja7101218

Publication Date (Web): March 12, 2008

†

California Institute of Technology.

‡

Huntington Medical Research Institutes.

Cambridge Isotope Laboratories.

In papers with more than one author, the asterisk indicates the name of the author to whom inquiries about the paper should be addressed.

, weitekamp@caltech.edu

Abstract

We use the PASADENA (parahydrogen and synthesis allow dramatically enhanced nuclear alignment) method to achieve ¹³C polarization of 20% in seconds in 1-¹³C-succinic-d₂ acid. The high-field ¹³C multiplets are observed as a function of pH, and the line broadening of C1 is pronounced in the region of the pK values. The ²J_CH, ³J_CH, and ³J_HH couplings needed for spin order transfer vary with pH and are best resolved at low pH leading to our use of pH 3 for both the molecular addition of parahydrogen to 1-¹³C-fumaric acid-d₂ and the subsequent transfer of spin order from the nascent protons to C1 of the succinic acid product. The methods described here may generalize to hyperpolarization of other carboxylic acids. The C1 spin−lattice relaxation time at neutral pH and 4.7 T is measured as 27 s in H₂O and 56 s in D₂O. Together with known rates of succinate uptake in kidneys, this allows an estimate of the prospects for the molecular spectroscopy of metabolism.