Parahydrogen Hyperpolarization Allows Direct NMR Detection of α-Amino Acids in Complex (Bio)mixtures

The scope of non-hydrogenative parahydrogen hyperpolarization (nhPHIP) techniques has been expanding over the last years, with the continuous addition of important classes of substrates. For example, pyruvate can now be hyperpolarized using the Signal Amplification By Reversible Exchange (SABRE) technique, offering a fast, efficient and low-cost PHIP alternative to Dynamic Nuclear Polarization for metabolic imaging studies. Still, important biomolecules such as amino acids have so far resisted PHIP, unless properly functionalized. Here, we report on an approach to nhPHIP for unmodified alpha-amino acids that allows their detection and quantification in complex mixtures at sub-micromolar concentrations. This method was tested on human urine, in which natural alpha-amino acids could be measured after dilution with methanol without any additional sample treatment.

Automated summary

In recent years, the scope of non-hydrogenative parahydrogen hyperpolarization (nhPHIP) techniques has been expanding, allowing for the detection and quantification of unmodified alpha-amino acids in complex mixtures. This method has shown great potential as demonstrated in human urine samples.