Determination of hydrogen exchange and relaxation parameters in PHIP complexes at micromolar concentrations

Abstract

Abstract. Non-hydrogenative para-hydrogen-induced polarization (PHIP) is a fast, efficient and relatively inexpensive approach to enhance nuclear magnetic resonance (NMR) signals of small molecules in solution. The efficiency of this technique depends on the interplay of NMR relaxation and kinetic processes, which, at high concentrations, can be characterized by selective inversion experiments. However, in the case of dilute solutions this approach is clearly not viable. Here, we present alternative PHIP-based NMR experiments to determine hydrogen and hydride relaxation parameters as well as the rate constants for para-hydrogen association with and dissociation from asymmetric PHIP complexes at micromolar concentrations. Access to these parameters is necessary to understand and improve the PHIP enhancements of (dilute) substrates present in, for instance, biofluids and natural extracts.

Understanding Parahydrogen Hyperpolarized Urine Spectra: The Case of Adenosine Derivatives

“…The method is not quantitative in the same way as traditional 1 H NMR, since multipulse NMR detection schemes and analyte-specific complex 3 dissociation kinetics [17], hydrogen exchange rate and relaxation [18] properties are involved. However, similarly to regular 2D NMR [19], quantification can be achieved by analyte-specific calibration curves [4][5][6][7][8][9]13].…”