Paramagnetic relaxation enhancement (PRE) is a useful source of information about electron-nucleus distances and also provides estimates of electron relaxation rates. Field dependence of spin relaxation in paramagnetic systems is contributed by the electronic effect and sometimes molecular dynamics. In spite of ultra-low field studies, the middle to high field range contains inter and intra-molecular dynamics. This issue shows two papers investigated paramagnetic systems in a wide field range to tens of Tesla range. ...
Strong nuclear spin-hyperpolarization irradiated by light-inducing has been investigated for decades. The biological applications on protein folding, surface accessibility, molecular interactions, etc. have been conducted and investigated in this manner. Despite liquid-state applications, the solid-state NMR has also employed such a manner additionally combining the magic-angle spinning (MAS) to gain the high-resolution on solid-state spectra. The group of Prof. Matysik demonstrated the capability of MAS field-cycling solid-state NMR on determination of field-dependent CIDNP (Chemical Induced Dynamics Polarization) effect on bacterial Rhodobactor(R.) spheroids wildtype. In their studies of field range from 0.2 to 20 Tesla, the reaction center of bacterial Rhodobactor(R.) spheroids wildtype showed the significant CIDNP enhancement on the magnetic field 5 Tesla, i.e. around 200MHz. Shown figure is the simulated trend for the enhancement due to the solid-state photo-CIDNP effect as a function of the magnetic field for two selected nuclei from the donor (PM) and the acceptor (Φ) cofactors. The presented curves are donor and acceptor on 4-13C-δ-Aminolevulinic acid (4-ALA) in bacterial Rhodobactor(R.) spheroids wildtype. [Ref: supplimental data from Scientific Reports 7, 12111 (2017)]
The following studies open different windows of applications on field-cycling NMR on the study of nuclear hyperpolarization.
The investigation of molecular motions by Nuclear Magnetic Resonance (NMR) relaxometry is commonly conducted in material science and proton dynamics. Field-dependent NMR has already proven to distinguish different types of liquid samples, such as alcohols, or ionic liquids, etc. In many food applications, they mainly contain liquid substances. Different compositions and viscosities create significant patterns on NMR relaxation, R1, and R2, and diffusion coefficient D. Instead of the conventional approach by varying the temperature, the field-dependent measurement could avoid material changes by the thermal perturbation. . . .
CIDNP (Chemical Induced Dynamic Nuclear Polarization) is a high-sensitivity method for photochemcial reactions investigation and radical studies. This manner is also able to apply on protein dynamics investigation, such as protein folding. Studies of CIDNP in weak magnetic fields even give additional infomration on radical reaction mechanisms and on exchange processes.
Studeis of low magnetic field photo-CIDNP require two mechanical breakthrough, one is a lumination unit, the other is a switcher of magnetic fields. Lumination unit was developed by ulterizaing specific wavelength laser and a light guide to the NMR tube. Nowadays, the lumination unit was alternatively performed by Light-emission diodes (LED) instead of laser lumination. As for the switcher of magnetic fields, one can imply field-cycler to carry the sample to the lowfield where the lumination unit is located. . . .
