2023/11/02 by Jacob R. Lindale, Lindale, Jacob R., L. L. Smith +9 · 2 citations
Biochemistry, Genetics and Molecular Biology · Chemistry · Materials Science · #Advanced NMR Techniques and Applications #Chemical Physics (physics.chem-ph) #Electron Spin Resonance Studies #FOS: Physical sciences #Quantum Physics (quant-ph) #Solid-state spectroscopy and crystallography
paper · pdf · doi:10.48550/arxiv.2311.01417
openalex publication_date 2023/11/02 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The inherently low signal-to-noise ratio of NMR and MRI is now being addressed by hyperpolarization methods. For example, iridium-based catalysts that reversibly bind both parahydrogen and ligands in solution can hyperpolarize protons (SABRE) or heteronuclei (X-SABRE) on a wide variety of ligands, using a complex interplay of spin dynamics and chemical exchange processes, with common signal enhancements between 103-104. This does not approach obvious theoretical limits, and further enhancement would be valuable in many applications (such as imaging mM concentration species in vivo). Most SABRE/X-SABRE implementations require far lower fields (μT-mT) than standard magnetic resonance (>1T), and this gives an additional degree of freedom: the ability to fully modulate fields in three dimensions. However, this has been underexplored because the standard simplifying theoretical assumptions in magnetic resonance need to be revisited. Here we take a different approach, an evolutionary strategy algorithm for numerical optimization, Multi-Axis Computer-aided HEteronuclear Transfer Enhancement for SABRE (MACHETE-SABRE). We find nonintuitive but highly efficient multi-axial pulse sequences which experimentally can produce a 10-fold improvement in polarization over continuous excitation. This approach optimizes polarization differently than traditional methods, thus gaining extra efficiency.