Simulations and Novel Catalytic Schemes for Sensitivity Enhancement in Biomedical Applications of Magnetic Resonance by Para-Hydrogen Induced Nuclear Polarization

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Parahydrogen Induced Polarization (PHIP) is a very efficient hyperpolarization technique for the signal-enhancement of NMR spectroscopy and MRI tomography. In the previous funding period, we developed an efficient PHIP labeling strategy for peptides, based on non-natural amino acids with unsaturated alkyl side chains. Incorporated into oligo-peptides, such as the sun-flower trypsin inhibitor SFTI-1, they gave very strong signal enhancements on the order of 1000, while retaining their bioactivity. Our main goal for the second project period is the development of additional PHIP-labels for 1H- or 13C-NMR applications to peptides and larger inhibitors such as knottins or affibodies. To this end, other non-natural amino acids with alkyl-bearing side chains suitable for solid-phase peptide synthesis will be synthesized. Since the lifetime of hyperpolarization, determined by its relaxation times, is crucial for many applications, we will employ as necessary selective 13C-labeling and selective deuteration of the alkyl groups to widen the kinetic window of PHIP. Test experiments on small model peptides will determine the marker's PHIP efficiency. The efficient markers are then incorporated into larger peptides and finally, the best ones, into the above-mentioned inhibitors. The ultimate goal is to find out, whether PHIP-enhanced NMR allows determination of the binding constants and kinetics of these inhibitors and their associated enzymes. For this purpose, the existing experimental setup will be modified so that it allows the injection of the enzyme after hyperpolarization of the inhibitors by PHIP. In parallel, we would like to continue the search for efficient PHIP labels for RNA aptamers, evaluate them on small models and apply them to the flavin mononucleotide (FMN) as an interesting targeting system.