Zero- to low-field relaxometry of chemical and biological fluids

Abstract

Nuclear magnetic resonance (NMR) relaxometry is an analytical method that provides information about molecular environments, even for NMR “silent” molecules (spin-0), by analyzing the properties of NMR signals versus the magnitude of the longitudinal field. Conventionally, this technique is performed at fields much higher than Earth’s magnetic field, but our work focuses on NMR relaxometry at zero and ultra-low magnetic fields (ZULFs). Operating under such conditions allows us to investigate slow (bio)chemical processes occurring on a timescale from milliseconds to seconds, which coincide with spin evolution. ZULFs also minimize T2 line broadening in heterogeneous samples resulting from magnetic susceptibility. Here, we use ZULF NMR relaxometry to analyze (bio)chemical compounds containing 1H-13C, 1H-15N, and 1H-31P spin pairs. We also detected high-quality ULF NMR spectra of human whole-blood at 0.8 μT, despite a shortening of spin relaxation by blood proteomes (e.g., hemoglobin). Information on proton relaxation times of blood, a potential early biomarker of inflammation, can be acquired in under a minute using inexpensive, portable/small-size NMR spectrometers based on atomic magnetometers.

Proton Relaxometry of Tree Leaves at Hypogeomagnetic Fields

“…The shielded regime is itself of fundamental interest, for example in studying properties of biological tissues under hypogeomagnetic conditions such as those encountered during long-distance spaceflight. Relaxometry studies of systems in which NMR signals originate from molecules other than water are also valuable, since other relaxation mechanisms can be involved [40]. While future experiments need not be limited to relaxometry of protons only, NMR-enabled investigation of plant water dynamics is highly warranted, particularly in ultralow and hypogeomagnetic regimes.…”

“…Relaxometry studies of systems in which NMR signals originate from molecules other than water are also valuable, since other relaxation mechanisms can be involved [40]. While future experiments need not be limited to relaxometry of protons only, NMR-enabled investigation of plant water dynamics is highly warranted, particularly in ultralow and hypogeomagnetic regimes.…”