Detecting Acetylated Aminoacids in Blood Serum using Hyperpolarized 13C-1Η-2D-NMR

Abstract Dynamic Nuclear Polarization (DNP) can substantially enhance the sensitivity of NMR experiments. Among the implementations of DNP, ex-situ dissolution DNP (dDNP) achieves high signal enhancement levels owing to a combination of a large temperature factor between 1.4 and 300K with the actual DNP effect in the solid state at 1.4K. For sufficiently long T 1 relaxation times much of the polarization can be preserved during dissolution with hot solvent, thus enabling fast experiments during the life time of the polarization. Unfortunately for many metabolites found in biological samples such as blood relaxation times are too short to achieve a significant enhancement. We have therefore introduced 13 C-carbonyl labelled acetyl groups as probes into amino acid metabolites using a simple reaction protocol. The advantage of such tags is a sufficiently long T 1 relaxation time, the possibility to enhance signal intensity by introducing 13 C, and the possibility to identify tagged metabolites in NMR spectra. We demonstrate feasibility for mixtures of amino acids and for blood serum. In two-dimensional dDNP-enhanced HMQC experiments of these samples acquired in 8 seconds we can identify acetylated amino acids and other metabolites based on small differences in chemical shifts.