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• Analysis of Pesticides in a Hemp Matrix

  Hemp is a strain of Cannabis sativa that has multiple industrial uses including paper, plastics, woven goods, and even food. While certain strains of Cannabis sativa are well-known for their use as a recreational drug due the presence of the psychoactive compound tetrahydrocannabinol (THC), hemp strains are defined by the U.S. federal government as those that contain less than 0.3% THC.1 Additionally, hemp strains typically contain more cannabidiol (CBD),2 which was recently approved by the FDA to treat certain types of epilepsy, and is currently being investigated as a medical treatment for other afflictions.
• Fast MAS solid-state NMR toolbox for biomolecules_NM210002E

  Solid-state NMR is a useful tool to elucidate protein structures. Although fully 13C and 15N labelled samples are required, solid-state NMR provides complementary or unique information that is not accessible by other typical methods. For example, there are, in principle, no upper or lower limits to molecular weight in solid-state NMR, unlike solution NMR and cryo EM. In addition, solid-state NMR is a very sensitive probe of local dynamics. One of the stumbling block of solid-state NMR is sample amount. Indeed, 20 – 50 mg of fully labelled (expensive!) samples are required for 3.2 mm / 4 mm MAS rotors. However, the recent developments allowing MAS rates above 70 kHz change the situation completely. [1] Indeed, the 0.75 mm (1 mm) MAS rotors used for fast MAS experiments (up to 120 (80) kHz) only require 290 (800) nL of sample, enabling solid-state NMR measurements on sub-milligram amounts of sample. Another great advantage of fast MAS is the averaging out of most of the anisotropic interactions, allowing the use of low power schemes (decoupling, recoupling, cross-polarization etc.), which in turns avoids sample heating. High resolution 1H spectra become readily available in these conditions, especially for microcrystalline proteins. This is the biggest advantage of fast MAS, since 1H detection dramatically improves sensitivity compared to traditional 13C detection. As a consequence, fast MAS solid-state NMR is now a versatile tool to study the structure and dynamics of biomolecules, for which the first step is sequence-specific resonance assignment. To this end, requisite experiments for sequential backbone and sidechain assignments are well established. [2] Here, we introduce the tool box available for the Delta software together with examples on fully protonated Het-s (226-280) protein.
• A 1H Solid State NMR Application for Pharmaceutical Development by using Ultra Fast MAS: Drug-Polymer Intermolecular Interaction on Solid Dispersions_NM190003E

  The low oral bioavailability of a drug due to its poor aqueous solubility is a major challenge for pharmaceutical development. Solid dispersion (SD), where the amorphous drug is dispersed into the polymer matrix, is one of the useful approaches to improve the aqueous solubility. However, thermodynamically unstable nature of an amorphous drug increases its susceptibility to recrystallize upon storage, which, in turn, reduces its solubility and dissolution. Therefore, design of thermodynamically stable SD is required.
• Experimental set-up of high-resolution 1H solid-state NMR by wPMLG_NM200010E

  1H, in principle, is very useful nucleus to investigate atomic-resolution structures and dynamics due to its high abundance (>99%) and gyromagnetic ratio (600 MHz at 14.1T). In fact 1H is the first choice of nucleus in solution NMR. On the other hand, 1H NMR of rigid solids is much less common. This is because 1H solid-state NMR gives very broad (~50 kHz) and featureless spectra (Fig 1a) due to strong 1H-1H dipolar coupling, which is dynamically averaged out in solution. Magic angle spinning (MAS) removes the broadening to the first order, but is not enough to achieve high resolution 1H NMR at moderate MAS rate (Fig 1b). Tremendous efforts were made to overcome this issue from the early dates of solid-state NMR towards high-resolution 1H NMR [1]. Most of them combine MAS with sophisticated 1H pulses which is dubbed CRAMPS (combined rotation and multiple pulse spectroscopy). Nowadays very fast MAS > 60 kHz can be used to achieve high-resolution 1H solid-state NMR (Fig 1c) [2]. However, the traditional CRAMPS is still useful as that can be performed with very conventional solid-state NMR equipment, for example 4 mm MAS probe with a 400 MHz spectrometer. Moreover, wPMLG at moderate MAS rate often overwhelms fast MAS in terms of resolution. In this note, we will describe tutorial guidance to optimize experimental parameters for CRAMPS.
• Efficient symmetry-based γ-encoded DQ recoupling sequences for suppression of t1-noise in solid-state NMR spectroscopy at fast MAS

  Solid-state NMR spectroscopy has played a significant role in elucidating the structure and dynamics of materials and biological solids at a molecular level for decades. In particular, the 1H double-quantum/single-quantum (DQ/SQ) chemical shift correlation experiment is widely used for probing the proximity of protons, rendering it a powerful tool for elucidating the hydrogen-bonding interactions and molecular packing of various complex molecular systems. Two factors, namely, the DQ filtering efficiency and t1-noise, dictate the quality of the 2D 1H DQ/SQ spectra. Experimentally different recoupling sequences show varied DQ filtering efficiencies and t1-noise. Herein, after a systematic search of symmetry-based DQ recoupling sequences, we report that the symmetry-based γ-encoded sequences show superior performance to other DQ recoupling sequences, which not only have a higher DQ recoupling efficiency but can also significantly reduce t1-noise. The origin of t1-noise is further discussed in detail via extensive numerical simulations. We envisage that such γ-encoded sequences are superior candidates for DQ recoupling in proton-based solid-state NMR spectroscopy due to its capability of efficiently exciting DQ coherences and suppressing t1-noise.
• Spectral Separation of mixtures by solid state NMR_NM180015E

  Solid state NMR is a powerful tool to obtain information in the crystalline state which would be lost in the solution state.