Abstract
In recent years, hyperpolarization of water protons via dissolution Dynamic Nuclear Polarization (dDNP) has attracted increasing interest in the magnetic resonance community. Hyperpolarized water may provide an alternative to Gd-based contrast agents for angiographic and perfusion Magnetic Resonance Imaging (MRI) examinations, and it may report on chemical and biochemical reactions and proton exchange while perfoming Nuclear Magnetic Resonance (NMR) investigations. However, hyperpolarizing water protons is challenging. The main reason is the presence of radicals, required to create the hyperpolarized nuclear spin state. Indeed, the radicals will also be the main source of relaxation during the dissolution and transfer to the NMR or MRI system. In this work, we report water magnetizations otherwise requiring a field of 10,000 T at room temperature on a sample of pure water, by employing dDNP via UV-generated, labile radicals. We demonstrate the potential of our methodology by acquiring a 15N spectrum from natural abundance urea with a single scan, after spontaneous magnetization transfer from water protons to nitrogen nuclei.
Highlights
In recent years, hyperpolarization of water protons via dissolution Dynamic Nuclear Polarization has attracted increasing interest in the magnetic resonance community
Water protons have played a crucial role for Nuclear Magnetic Resonance (NMR)
The reason is the weak nuclear magnetic moment of 1H nuclei that leads to only few tens of ppm net polarization of the spins at ordinary values of magnetic field and room temperature
Summary
Hyperpolarization of water protons via dissolution Dynamic Nuclear Polarization (dDNP) has attracted increasing interest in the magnetic resonance community. Magnetic Resonance Imaging (MRI) exploits the magnetism from water protons of the human body to non-invasively visualize organs and tissues[5] All these applications suffer from a main drawback: low sensitivity[6]. Fast exchange with HP water 1H nuclei has been used to enhance the sensitivity and reduce the scanning time in 1D and 2D MRS experiments on biomolecules dynamics, protein structure determination and protein–ligands interaction[16,17,18,19,20] These studies have demonstrated the potential of HP water as an eclectic analytical tool; its use is still limited since hyperpolarization of water protons is challenging. Compared to 13C, the large magnetic moment and density of protons guarantee high and fast DNP in the solid state, when broad ESR line radicals such as nitroxides are used[25]
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