Toward Applications of β-NMR Spectroscopy in Chemistry and Biochemistry

Abstract

Applications of nuclear spectroscopic techniques are well established in chemistry and biochemistry, where, for example, conventional nuclear magnetic resonance (NMR) spectroscopy is an indispensable analytical tool [1]. NMR is used routinely to identify small organic molecules in quality control, and in more complex research applications to elucidate structure and dynamics of large biomolecules such as proteins and nucleic acids. Additionally, magnetic resonance (MR) scanners are available at most large hospitals for imaging, and it is now even possible to acquire affordable desk top NMR instruments with permanent magnets, aimed at small businesses and educational institutions. However, conventional NMR spectroscopy faces certain limitations, mainly due to: (1) relatively poor sensitivity and (2) the fact that there are elements that are difficult to detect, because of poor NMR response. To overcome the first problem, a variety of hyperpolarization techniques have been developed, reaching nuclear spin polarization in the % range [2], which is far beyond what may be achieved at thermal equilibrium even in strong external magnetic fields at room temperature. β-detected NMR (β-NMR) spectroscopy belongs to this family of specialized NMR techniques, where considerable nuclear spin polarization is created prior to the NMR measurement. The sensitivity of β-NMR spectroscopy is further enhanced, as it is a radioisotope-based technique, exploiting the detection of anisotropic emission of β-particles from the spin polarized nuclei, vide infra, leading to a billion-fold or higher increase in sensitivity as compared to conventional NMR spectroscopy on stable isotopes. In addition to this, some of the elements which are problematic in conventional NMR spectroscopy, such as Mg, Ca, Cu, and Zn, already are or might be accessible with β-NMR spectroscopy [3–5]. Several applications of β-NMR spectroscopy in nuclear, solid state physics, and materials science have been published over the past decades [3–14] and references therein, and with the project described herein, we aim to advance the applications to solution chemistry and biochemistry [5].