Microtesla SABRE enables 10% nitrogen-15 nuclear spin polarization

Area of Science:

• Nuclear Magnetic Resonance (NMR) Spectroscopy
• Quantum Chemistry
• Biophysics

Background:

• Hyperpolarization techniques significantly enhance NMR signal sensitivity.
• Nitrogen-15 (15N) is a crucial nucleus for molecular imaging and metabolic studies.
• Current hyperpolarization methods can be complex and costly.

Purpose of the Study:

• To demonstrate efficient nuclear spin hyperpolarization of nitrogen-15 in biologically relevant molecules.
• To introduce a novel, cost-effective hyperpolarization method.
• To explore the potential of this technique for in vivo applications.

Main Methods:

• Utilizing parahydrogen and "signal amplification by reversible exchange" (SABRE) at microtesla fields.
• Performing SABRE within a magnetic shield to achieve efficient spin polarization transfer.
• Transferring hyperpolarized samples to a conventional NMR spectrometer for signal detection.

Main Results:

• Achieved ∼30,000-fold and ∼20,000-fold enhancements in (15)N NMR signals for pyridine and nicotinamide, respectively.
• Reached nuclear spin polarizations of ∼10% and ∼7% for pyridine and nicotinamide at 9.4 T.
• Demonstrated the effectiveness of the "SABRE in shield enables alignment transfer to heteronuclei" (SABRE-SHEATH) method.

Conclusions:

• SABRE-SHEATH provides a simple and cost-effective approach for hyperpolarizing heteronuclei like (15)N.
• The method offers potential advantages for in vivo NMR/MRI due to long hyperpolarization lifetimes and minimal background signals.
• Facile chemical-shift discrimination of different species enhances its utility for biological studies.