Generating long-lasting H1 and C13 hyperpolarization in small molecules with parahydrogen-induced polarization

Abstract

Recently, Levitt and co-workers demonstrated that conserving the population of long-lasting nuclear singlet states in weak magnetic fields can lead to a preservation of nuclear spin information over times substantially longer than governed by the (high-field) spin-lattice relaxation time T1. Potential benefits of the prolonged spin information for magnetic resonance imaging and spectroscopy were pointed out, particularly when combined with the parahydrogen induced polarization (PHIP) methodology. In this contribution, we demonstrate that an increase of the effective relaxation time by a factor up to three is achieved experimentally, when molecules hyperpolarized by PHIP are kept in a weak magnetic field instead of the strong field of a typical NMR magnet. This increased lifetime of spin information makes the known PHIP phenomena more compatible with the time scales of biological processes and, thus, more attractive for future investigations.

New Technologies for Human Cancer Imaging

“…For example, hyperpolarized carbon 13 pyruvate permits high sensitivity detection of tumors in animals. 50 Although the half-life of this improved spin state is typically short, the innovative use of weak magnetic fields 51 and alternative atoms to prolong the effect are exciting avenues of investigation.…”

Effect of low and zero magnetic field on the hyperpolarization lifetime in parahydrogenated perdeuterated molecules

“…In this case the symmetry is broken only when the parahydrogenated molecule is transferred into a high-field NMR spectrometer. This behavior has been experimentally assessed in parahydrogenated molecules and hyperpolarization storage was observed also when the two parahydrogen protons are coupled to other protons [12,13]. In the latter case it has been shown that three singlet states are formed in proportion of a function of J coupling constants.…”

Isotropic filtering using polyhedral phase cycles: Application to singlet state NMR

“…In some cases, singlet nuclear spin states have long decay time constants T S which may exceed the spin-lattice relaxation time T 1 by an order of magnitude or more [12][13][14][15][16][17][18][19][20][21]. Such long-lived states have been used to study slow diffusional motion and chemical exchange [16,18].…”

“…Such long-lived states have been used to study slow diffusional motion and chemical exchange [16,18]. Applications are anticipated for transporting and storing hyperpolarized spin order generated by chemical reactions of parahydrogen [19]. The existence of long-lived spin states in systems of more than two coupled spins has been discussed [15,20,21].…”

“…Traditional phase cycles, which are based on the rotational properties of spin order terms around the z-axis, cannot distinguish this term from higher-rank components which also have l ¼ 0. As described below, isotropic spin order is of particular interest in solution NMR, since it is a manifestation of singlet spin populations, which can have very long lifetimes in some circumstances [12][13][14][15][16][17][18][19][20][21].…”