Accurate Measurement of Longitudinal Cross-Relaxation Rates in Nuclear Magnetic Resonance

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Determination of the antisymmetric part of the chemical shift anisotropy tensor via spin relaxation in nuclear magnetic resonance

Geoffrey Bodenhausen

Relaxation processes induced by the antisymmetric part of the chemical shift anisotropy tensor (henceforth called anti-CSA) are usually neglected in NMR relaxation studies. It is shown here that anti-CSA components contribute to longitudinal relaxation rates of the indole N-15 nucleus in tryptophan in solution at different magnetic fields and temperatures. To determine the parameters of several models for rotational diffusion and internal dynamics, we measured the longitudinal relaxation rates R-1=1/T-1 of N-15, the N-15-H-1 dipole-dipole (DD) cross-relaxation rates (Overhauser effects), and the cross-correlated CSA/DD relaxation rates involving the second-rank symmetric part of the CSA tensor of N-15 at four magnetic fields B-0=9.4, 14.1, 18.8, and 22.3 T (400, 600, 800, and 950 MHz for protons) over a temperature range of 270

American Institute of Physics2010

Nanodiamond Relaxometry-Based Detection of Free-Radical Species When Produced in Chemical Reactions in Biologically Relevant Conditions

Mayeul Sylvain Chipaux

Diamond magnetometry is a quantum sensing method involving detection of magnetic resonances with nanoscale resolution. For instance, T1 relaxation measurements, inspired by equivalent concepts in magnetic resonance imaging (MRI), provide a signal that is equivalent to T1 in conventional MRI but in a nanoscale environment. We use nanodiamonds (between 40 and 120 nm) containing ensembles of specific defects called nitrogen vacancy (NV) centers. To perform a T1 relaxation measurement, we pump the NV center in the ground state (using a laser at 532 nm) and observe how long the NV center can remain in this state. Here, we use this method to provide real-time measurements of free radicals when they are generated in a chemical reaction. Specifically, we focus on the photolysis of H2O2 as well as the so-called Haber-Weiss reaction. Both of these processes are important reactions in biological environments. Unlike other fluorescent probes, diamonds are able to determine spin noise from different species in real time. We also investigate different diamond probes and their ability to sense gadolinium spin labels. Although this study was performed in a clean environment, we take into account the effects of salts and proteins that are present in a biological environment. We conduct our experiments with nanodiamonds, which are compatible with intracellular measurements. We perform measurements between 0 and 10(8) nM, and we are able to reach detection limits down to the nanomolar range and typically find T1 times of a few 100 mu s. This is an important step toward label-free nano-MRI signal quantification in biological environments.

AMER CHEMICAL SOC2020

Method for nmr spectrometry or mri measurement using dissolution dynamic nuclear polarization (dnp) with scavenging of free radicals

Geoffrey Bodenhausen, Sami Jannin, Pascal Miéville

PROBLEM TO BE SOLVED: To provide a method for extending longitudinal relaxation time and transverse relaxation time in nuclear magnetic resonance (NMR), while removing free radicals from hyperpolarized solution. SOLUTION: A method for preparing samples for magnetic resonance measurement by using dissolution dynamic nuclear polarization-based hyperpolarization, includes the step (1.1) to prepare frozen beads of a first kind containing paramagnetic substances in addition to a solute under examination; the step (2.1) to insert the frozen beads into a polarization magnet; the step (3.1) to create a higher polarization state of the nuclei in a magnetic field; the step (4.1) to heat the sample up to room temperature, the step (5.1) to transfer samples into MR magnet; and the step (6.1) to perform MR measurement. Further, additional steps are included, the step (1.2) to prepare frozen beads of a second kind containing a reduction agent, and the step (2.2) to insert the frozen beads of a second kind together with the frozen beads of the first kind into the polarization magnet. ;COPYRIGHT: (C)2011,JPO&INPIT

2011