From the environment to NMR: water suppression for whole samples in their native state

NMR applied to living organisms is arguably the ultimate tool for understanding environmental stress responses and can provide desperately needed information on toxic mechanisms, synergistic effects, sublethal impacts, recovery, and biotransformation of xenobiotics. To perform in vivo NMR spectroscopy, a flow cell system is required to deliver oxygen and food to the organisms while maintaining optimal line shape for NMR spectroscopy. In this tutorial, two such flow cell systems and their constructions are discussed: (a) a single pump high‐volume flow cell design is simple to build and ideal for organisms that do not require feeding (i.e., eggs) and (b) a more advanced low‐volume double pump flow cell design that permits feeding, maintains optimal water height for water suppression, improves locking and shimming, and uses only a small recirculating volume, thus reducing the amount of xenobiotic required for testing. In addition, key experimental aspects including isotopic enrichment, water suppression, and 2D experiments for both 13C enriched and natural abundance organisms are discussed.

Section: Nmr Experiments For In Vivo Flow Nmrmentioning

confidence: 95%

Section: Nmr Experiments For In Vivo Flow Nmrmentioning

confidence: 99%

Flow‐based in vivo NMR spectroscopy of small aquatic organisms

Soong

Mobarhan

Tabatabaei

et al. 2019

“…As such, if the goal of the MAS study is to follow metabolic responses or toxic impacts, it may be preferable to put the D 2 O in a sealed 0.5‐mm capillary containing 5–10 μL D 2 O placed in the bottom of the rotor as an external lock system. The details on how to make these lock capillaries have been provided elsewhere …”

Section: Sample Preperation Handling and Spinningmentioning

confidence: 99%

“…In many ways, CMP NMR can be thought of as changing NMR technology to match natural samples, rather than changing the sample to match a specific NMR technique. CMP NMR has permitted the study of structural interactions and processes in unaltered heterogeneous samples, including soil, swelling of rubber by biofuels, intact plants, and to follow biological processes (seed growth) …”

Section: Introductionmentioning

confidence: 99%

In vivo comprehensive multiphase NMR

Mobarhan

Soong

Lane

et al. 2019

Traditionally, due to different hardware requirements, nuclear magnetic resonance (NMR) has developed as two separate fields: one dealing with solids, and one with solutions. Comprehensive multiphase (CMP) NMR combines all electronics and hardware (magic angle spinning [MAS], gradients, high power Radio Frequency (RF) handling, lock, susceptibility matching) into a universal probe that permits a comprehensive study of all phases (i.e., liquid, gel‐like, semisolid, and solid), in intact samples. When applied in vivo, it provides unique insight into the wide array of bonds in a living system from the most mobile liquids (blood, fluids) through gels (muscle, tissues) to the most rigid (exoskeleton, shell). In this tutorial, the practical aspects of in vivo CMP NMR are discussed including: handling the organisms, rotor preparation, sample spinning, water suppression, editing experiments, and finishes with a brief look at the potential of other heteronuclei (2H, 15N, 19F, 31P) for in vivo research. The tutorial is aimed as a general resource for researchers interested in developing and applying MAS‐based approaches to living organisms. Although the focus here is CMP NMR, many of the approaches can be adapted (or directly applied) using conventional high‐resolution magic angle spinning, and in some cases, even standard solid‐state NMR probes.

“…In the original sequence, presaturation was used for water suppression. In HR‐MAS as the water signal is narrowed by MAS, presaturation is quite effective for samples with small to moderate water signals but fails in the presence of broad intense water . To demonstrate the improvement of W5 in complex samples, Figure compares the lipid suppression sequence using presaturation and W5‐WATERGATE on tartar sauce.…”

Section: Resultsmentioning

confidence: 99%

Improvements in lipid suppression for ¹H NMR‐based metabolomics: Applications to solution‐state and HR‐MAS NMR in natural and in vivo samples

Hassan

Majumdar

et al. 2019

Proton nuclear magnetic resonance (NMR) spectra of intact biological samples often show strong contributions from lipids, which overlap with signals of interest from small metabolites. Pioneering work by Diserens et al. demonstrated that the relative differences in diffusivity and relaxation of lipids versus small metabolites could be exploited to suppress lipid signals, in high‐resolution magic angle spinning (HR‐MAS) NMR spectroscopy. In solution‐state NMR, suspended samples can exhibit very broad water signals, which are challenging to suppress. Here, improved water suppression is incorporated into the sequence, and the Carr‐Purcell‐Meiboom‐Gill sequence (CPMG) train is replaced with a low‐power adiabatic spinlock that reduces heating and spectral artefacts seen with longer CPMG filters. The result is a robust sequence that works well in both HR‐MAS as well as static solution‐state samples. Applications are also extended to include in vivo organisms. For solution‐state NMR, samples containing significant amount of fats such as milk and hemp hearts seeds are used to demonstrate the technique. For HR‐MAS, living earthworms (Eisenia fetida) and freshwater shrimp (Hyalella azteca) are used for in vivo applications. Lipid suppression techniques are essential for non‐invasive NMR‐based analysis of biological samples with a high‐lipid content and adds to the suite of experiments advantageous for in vivo environmental metabolomics.