Microtesla SABRE Enables 10% Nitrogen-15 Nuclear Spin Polarization

Abstract

Parahydrogen is demonstrated to efficiently transfer its nuclear spin hyperpolarization to nitrogen-15 in pyridine and nicotinamide (vitamin B3 amide) by conducting “signal amplification by reversible exchange” (SABRE) at microtesla fields within a magnetic shield. Following transfer of the sample from the magnetic shield chamber to a conventional NMR spectrometer, the 15N NMR signals for these molecules are enhanced by ∼30,000- and ∼20,000-fold at 9.4 T, corresponding to ∼10% and ∼7% nuclear spin polarization, respectively. This method, dubbed “SABRE in shield enables alignment transfer to heteronuclei” or “SABRE-SHEATH”, promises to be a simple, cost-effective way to hyperpolarize heteronuclei. It may be particularly useful for in vivo applications because of longer hyperpolarization lifetimes, lack of background signal, and facile chemical-shift discrimination of different species.

Symmetry constraints on spin dynamics: Application to hyperpolarized NMR

“…The transformation of total spin magnetization into singlet order, and back again, is an important manipulation in the NMR of long-lived states [13,14,15,16,17,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44] and in parahydrogen-enhanced NMR [18,19,20,21,22,45,46,47,48,49].…”

“…This result is well-known. For example, in parahydrogen-enhanced NMR, the chemical equivalence of the hydrogen nuclei originating with parahydrogen must be broken in order to obtain enhanced NMR signals [18,19,20,21,22,45,46,47,48,49]. The breaking of chemical equivalence is also necessary to access singlet order in spin-pair systems, for similar reasons.…”

“…I examine closely the spin dynamical manipulations of four-spin systems, involving long-lived spin states [13,14,15,16,17] and SABRE (Signal Amplification by Reversible Exchange) experiments [18,19,20,21,22]. Such experiments sometimes involve four-spin-1/2 systems of the type A 2 X 2 (two magnetically equivalent pairs) or AA XX (two chemically equivalent but magnetically inequivalent pairs).…”

“…As discussed below, such symmetry-imposed bounds are relevant to several experiments of current interest, such as SABRE [18,19,20,21,22].…”

A Hyperpolarizable 1H Magnetic Resonance Probe for Signal Detection 15 Minutes after Spin Polarization Storage

“…The dormant magnetism of p ‐H 2 transfers into the target through the scalar‐coupling framework of these catalysts as illustrated in Scheme 1. Since its inception, this method has stimulated many developments which include the hyperpolarization of a large class of molecules comprising of 1 H, 13 C, 15 N, and 31 P nuclei 11, 12, 13, 14. When compared to dissolution DNP, SABRE provides a low cost alternative that takes just seconds to hyperpolarize the agent in a continuous process that, while being inherently simple in concept, can be augmented by rf excitation 15…”