Sensitivity enhancement by parahydrogen hyperpolarization allows NMR detection and quantification of hundreds of urinary metabolites at down to nanomolar concentrations.
The scope of non-hydrogenative parahydrogen hyperpolarization (nhPHIP) techniques has been expanding over the last years,w ith the continuous addition of important classes of substrates.F or example,p yruvate can nowb e hyperpolarized using the Signal Amplification By Reversible Exchange (SABRE) technique,o ffering af ast, efficient and low-cost PHIP alternative to Dynamic Nuclear Polarization for metabolic imaging studies.S till, important biomolecules such as amino acids have so far resisted PHIP,unless properly functionalized. Here,wereport on an approach to nhPHIP for unmodified a-amino acids that allows their detection and quantification in complex mixtures at sub-micromolar concentrations.This method was tested on human urine,inwhich natural a-amino acids could be measured after dilution with methanol without any additional sample treatment.
The scope of non-hydrogenative parahydrogen hyperpolarization (nhPHIP) techniques has been expanding over the last years,w ith the continuous addition of important classes of substrates.F or example,p yruvate can nowb e hyperpolarized using the Signal Amplification By Reversible Exchange (SABRE) technique,o ffering af ast, efficient and low-cost PHIP alternative to Dynamic Nuclear Polarization for metabolic imaging studies.S till, important biomolecules such as amino acids have so far resisted PHIP,unless properly functionalized. Here,wereport on an approach to nhPHIP for unmodified a-amino acids that allows their detection and quantification in complex mixtures at sub-micromolar concentrations.This method was tested on human urine,inwhich natural a-amino acids could be measured after dilution with methanol without any additional sample treatment.
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.
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