Hyperpolarized Water Boosts NMR Signal Intensities

Researchers in Vienna have achieved crystal-clear views of protein structures after developing a method to improve the resolution of nuclear magnetic resonance (NMR).

NMR spectroscopy measures the magnetic properties of atoms and is the standard method for studying molecular structures. However, certain molecular events are too fast to be characterized via NMR. For example, protein folding—a crucial process during which amino acid chains adopt a 3D structure and functionality—takes just milliseconds.

A new advanced NMR technique described in Nature Protocols uses hyperpolarized water to significantly enhance signal strength and enable the monitoring of fast and complicated biomolecular events.  Using this dissolution DNP (D-DNP) method, an over 10,000-fold improvement in signal can be achieved. “The hyperpolarized water acts as a booster for the NMR signals of a protein during the measurement,” says Dennis Kurzbach from the Institute of Biological Chemistry at University of Vienna and deputy head of the NMR Centre of the Faculty of Chemistry. “The hydrogen nuclei of the hyperpolarized water are exchanged with those of the proteins, thus transferring the signal strength to the latter.”

With DNP, researchers can record an NMR spectrum every 100 milliseconds and use it to track the 3-D coordinates of individual amino acids and how they change over time. “This allows us to monitor processes that occur in milliseconds and distinguish individual atoms,” says Kurzbach, whose research focuses on developing new methods.

The protocols paper provides detailed instructions, from hyperpolarization to the transfer of the hyperpolarized water to the NMR spectrometer, to the mixing of the hyperpolarized water with the sample solution, and the NMR measurement. It also presents six examples for method application, including the observation of protein folding or even the interactions of RNA and RNA-binding proteins as the basis for gene expressions in the cell.

According to the authors, the new method can be used for specific studies of RNA, DNA and polypeptides, especially when signal enhancement reaches the ‘magic’ number of 1,000-fold.

An NMR spectrometer equipped with a hyperpolarization prototype is a prerequisite for NMR boosted by hyperpolarized water, but such systems are not common. The Faculty of Chemistry of the University of Vienna is equipped with a DDNP-NMR device since 2020, which was constructed by Kurzbach based on an ERC Starting Grant.