Cotton Defoliation Guide in Texas.

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Chemical reaction monitoring using zero-field nuclear magnetic resonance enables study of heterogeneous samples in metal containers

We demonstrate that heterogeneous/biphasic chemical reactions can be monitored with high spectroscopic resolution using zero-field nuclear magnetic resonance spectroscopy. This is possible because magnetic susceptibility broadening is negligible at ultralow magnetic fields. We show the two-step hydrogenation of dimethyl acetylenedicarboxylate with para-enriched hydrogen gas in conventional glass NMR tubes, as well as in a titanium tube. The low frequency zero-field NMR signals ensure that there is no significant signal attenuation arising from shielding by the electrically conductive sample container. This method paves the way for in situ monitoring of reactions in complex heterogeneous multiphase systems and in reactors made of conductive materials while maintaining resolution and chemical specificity

Possible Applications of Dissolution Dynamic Nuclear Polarization in Conjunction with Zero- to Ultralow-Field Nuclear Magnetic Resonance

The combination of a powerful and broadly applicable nuclear hyperpolarization technique with emerging (near-)zero-field modalities offer novel opportunities in a broad range of nuclear magnetic resonance spectroscopy and imaging applications, including biomedical diagnostics, monitoring catalytic reactions within metal reactors and many others. These are discussed along with a roadmap for future developments.Comment: 12 pages, 5 figure

Rapid hyperpolarization and purification of the metabolite fumarate in aqueous solution

Hyperpolarized fumarate is a promising biosensor for carbon-13 magnetic resonance metabolic imaging. Such molecular imaging applications require nuclear hyperpolarization to attain sufficient signal strength. Dissolution dynamic nuclear polarization is the current state-of-the-art methodology for hyperpolarizing fumarate, but this is expensive and relatively slow. Alternatively, this important biomolecule can be hyperpolarized in a cheap and convenient manner using parahydrogen-induced polarization. However, this process requires a chemical reaction, and the resulting solutions are contaminated with the catalyst, unreacted reagents, and reaction side-product molecules, and are hence unsuitable for use in vivo. In this work we show that the hyperpolarized fumarate can be purified from these contaminants by acid precipitation as a pure solid, and later redissolved to a desired concentration in a clean aqueous solvent. Significant advances in the reaction conditions and reactor equipment allow for formation of hyperpolarized fumarate at ¹³C polarization levels of 30–45%

Advances in parahydrogen-enhanced nuclear magnetic resonance

Nuclear magnetic resonance is a powerful spectroscopic tool, which has found applications in fields such as chemistry, the life sciences, medical imaging, and even fundamental physics, but is often limited by the low polarization of nuclear spins in ambient conditions. Hyperpolarization techniques are used to increase the spin polarization, which can lead to large signal enhancements. In the context of magnetic resonance imaging, this can allow for in vivo observation of metabolites at physiological concentrations, which would otherwise not be possible given current sensitivity limits.This thesis describes a number of hyperpolarization methods and their applications to in vivo imaging, with particular emphasis on parahydrogen-induced hyperpolarization. This technique allows for the production hyperpolarized samples via chemical reaction with a specific spin-isomer of hydrogen gas. Theory and experiments for producing hyperpolarized samples are described that advance this methodology towards eventual clinical applicatio

Synergies between hyperpolarized NMR and microfluidics: a review

Hyperpolarized nuclear magnetic resonance and lab-on-a-chip microfluidics are two dynamic, but until recently quite distinct, fields of research. Recent developments in both areas increased their synergistic overlap. By microfluidic integration, many complex experimental steps can be brought together onto a single platform. Microfluidic devices are therefore increasingly finding applications in medical diagnostics, forensic analysis, and biomedical research. In particular, they provide novel and powerful ways to culture cells, cell aggregates, and even functional models of entire organs. Nuclear magnetic resonance is a non-invasive, high-resolution spectroscopic technique which allows real-time process monitoring with chemical specificity. It is ideally suited for observing metabolic and other biological and chemical processes in microfluidic systems. However, its intrinsically low sensitivity has limited its application. Recent advances in nuclear hyperpolarization techniques may change this: under special circumstances, it is possible to enhance NMR signals by up to 5 orders of magnitude, which dramatically extends the utility of NMR in the context of microfluidic systems. At the same time, hyperpolarization requires complex chemical and/or physical manipulations, which in turn may benefit from microfluidic implementation. In fact, many hyperpolarization methodologies rely on processes that are more efficient at the micro-scale, such as molecular diffusion, penetration electromagnetic radiation into the sample, or restricted molecular mobility on a surface. In this review we examine the confluence between the fields of hyperpolarization-enhanced NMR and microfluidics, and assess how these areas of research have mutually benefited one another, and will continue to do so

Zero- to ultralow-field nuclear magnetic resonance J-spectroscopy with commercial atomic magnetometers

Zero- to ultralow-field nuclear magnetic resonance (ZULF NMR) is an alternative spectroscopic method to high-field NMR, in which samples are studied in the absence of a large magnetic field. Unfortunately, there is a large barrier to entry for many groups, because operating the optical magnetometers needed for signal detection requires some expertise in atomic physics and optics. Commercially available magnetometers offer a solution to this problem. Here we describe a simple ZULF NMR configuration employing commercial magnetometers, and demonstrate sufficient functionality to measure samples with nuclear spins prepolarized in a permanent magnet or initialized using parahydrogen. This opens the possibility for other groups to use ZULF NMR, which provides a means to study complex materials without magnetic susceptibility-induced line broadening, and to observe samples through conductive materials.Comment: 6 pages, 5 figure

Real Time Nuclear Magnetic Resonance Detection of Fumarase Activity using Parahydrogen-Hyperpolarized [1-13C]fumarate

Hyperpolarized fumarate can be used as a probe of real-time metabolism in vivo, using carbon-13 magnetic resonance imaging. Dissolution dynamic nuclear polarization is commonly used to produce hyperpolarized fumarate, but a cheaper and faster alternative is to produce hyperpolarized fumarate via PHIP (parahydrogen induced polarization). In this work we trans-hydrogenate [1-13C]acetylene dicarboxylate with para-enriched hydrogen using a commercially available Ru catalyst in water to produce hyperpolarized [1-13C]fumarate. We show that fumarate is produced in 89% yield, with succinate as a side product in 11% yield. The proton polarization is converted into 13C magnetization using a constant adiabaticity field cycle, and a polarization level of 25% is achieved using 86% para-enriched hydrogen gas. We inject the hyperpolarized [1-13C]fumarate into cell suspensions and track the metabolism. This work opens the path to greatly accelerated preclinical studies using fumarate as a biomarker