19F-detected dual-optimized inverted 1JCC 1,n-ADEQUATE Modification of the recently reported 19F-detected 1,1-ADEQUATE experiment that incorporates dual-optimization to selectively invert a wide range of 1JCC correlations in a 1,n-ADEQUATE experiment is reported. Parameters for the dual-optimization segment of the pulse sequence were modified to accommodate the increased size of 1JCC homonuclear coupling constants of poly- and perfluorinated molecules relative to protonated molecules to allow broadband inversion of the 1JCC correlations. The observation and utility of isotope shifts are reported for the first time for 1,1- and 1,n-ADEQUATE correlations. October 22, 2021 NMR Peer-Reviewed Articles, Nuclear Magnetic Resonance (NMR) 0 Comment Read More >>
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. September 17, 2021 Nuclear Magnetic Resonance (NMR), Solid State NMR 0 Comment Read More >>
Metal-Templated Oligomeric Macrocyclization via Coupling for Metal-Doped π-Systems A method for the synthesis of metal-doped aromatic macrocycles has been developed. The method, i.e., metal-templated oligomeric macrocyclization via coupling, adopts Ni as the template and assembles five pyridine units via a Ni-mediated coupling reaction to form aryl–aryl linkages. A pentameric oligopyridyl macrocycle was selectively obtained in good yield, and the reaction was also applicable to a gram-scale synthesis. The pentameric oligopyridyl macrocycle captured d8-Ni(II) at the center to form a paramagnetic pentagonal-bipyramidal complex. The method was applied to the synthesis of a large π-molecule to afford a nanometer-sized, bowl-shaped molecule having a unique combination of 120π and 8d electrons. September 17, 2021 NMR Peer-Reviewed Articles, Nuclear Magnetic Resonance (NMR) 0 Comment Read More >>
Material Evaluation using msFineAnalysis - MSTips 330 As polymer materials have become more complex and diverse, the details of their chemical composition have become more critical for the end users. This knowledge allows manufacturers and users to understand the effects of incorporating these polymer materials into their products. Additionally, it is critical to also have tools that can quickly compare two-samples to each other like conventional materials versus alternative materials, new products versus old products, and good products versus defective products. September 3, 2021 AccuTOF™ GC, Application Note, Mass Spectrometry (MS), Materials, msFineAnalysis 0 Comment Read More >>
Optically active covalent organic frameworks and hyperbranched polymers with chirality induced by circularly polarized light Axial chirality was induced by circularly polarized light to covalent organic frameworks as well as hyperbranched polymers composed of bezene-1,3,5-triyl core units and oligo(benzene-1,4-diyl) as linker units where variation in induction efficiency was rationally interpreted in terms of internal rotation dynamics studied through CPMAS 13C NMR experiments including CODEX measurements. August 20, 2021 NMR Peer-Reviewed Articles, Nuclear Magnetic Resonance (NMR) 0 Comment Read More >>
Structure Solution of Nano-Crystalline Small Molecules Using MicroED and Solid-State NMR Dipolar-Based Experiments Three-dimensional electron diffraction crystallography (microED) can solve structures of sub-micrometer crystals, which are too small for single crystal X-ray crystallography. However, R factors for the microED-based structures are generally high because of dynamic scattering. That means R factor may not be reliable provided that kinetic analysis is used. Consequently, there remains ambiguity to locate hydrogens and to assign nuclei with close atomic numbers, like carbon, nitrogen, and oxygen. Herein, we employed microED and ssNMR dipolar-based experiments together with spin dynamics numerical simulations. The NMR dipolar-based experiments were 1H-14N phase-modulated rotational-echo saturation-pulse double-resonance (PM-S-RESPDOR) and 1H-1H selective recoupling of proton (SERP) experiments. The former examined the dephasing effect of a specific 1H resonance under multiple 1H-14N dipolar couplings. The latter examined the selective polarization transfer between a 1H-1H pair. The structure was solved by microED and then validated by evaluating the agreement between experimental and calculated dipolar-based NMR results. As the measurements were performed on 1H and 14N, the method can be employed for natural abundance samples. Furthermore, the whole validation procedure was conducted at 293 K unlike widely used chemical shift calculation at 0 K using the GIPAW method. This combined method was demonstrated on monoclinic l-histidine. August 20, 2021 NMR Peer-Reviewed Articles, Nuclear Magnetic Resonance (NMR) 0 Comment Read More >>
Determination of the chemical shift tensor anisotropy and asymmetry of strongly dipolar coupled protons under fast MAS Orientationally-dependent interactions such as dipolar coupling, quadrupolar coupling, and chemical shift anisotropy (CSA) contain a wealth of spatial information that can be used to elucidate molecular conformations and dynamics. To determine the sign of the chemical shift tensor anisotropy parameter (δaniso), both the |m| = 1 and |m| = 2 components of the CSA need to be symmetry allowed, while the recoupling of the |m| = 1 term is accompanied with the reintroduction of homonuclear dipolar coupling components. Therefore, previously suggested sequences which solely recouple the |m| = 2 term cannot determine the sign a 1H's δaniso in a densely-coupled network. In this study, we demonstrate the CSA recoupling of strongly dipolar coupled 1H spins using the Cnn/1(9003601805400360180900) sequence. This pulse scheme recouples both the |m| = 1 and |m| = 2 CSA terms but the scaling factors for the homonuclear dipolar coupling terms are zeroed. Consequently, the sequence is sensitive to the sign of δaniso but is not influenced by homonuclear dipolar interactions. August 4, 2021 NMR Peer-Reviewed Articles, Nuclear Magnetic Resonance (NMR) 0 Comment Read More >>
Dioxins analysis using GC-MS/MS and software "TQ-DioK" - MSTips38 Dioxins are a general term for polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). Their structures consist of two chlorinated rings. Many congeners differ in terms of number of chlorine atoms and binding sites (Fig. 1). These substances are considered as persistent organic pollutants (POPS) due to their presence in the environment and the health risks associated. A World Health Organization (WHO) study has demonstrated the health risks (carcinogenic and immunotoxic) when population are exposed to them. In addition, dioxins have been regulated by the Stockholm convention on POPs in May 2001. In particular, 17 substances have to be monitored because they are regulated (7 PCDDs and 10 PCDFs). The highest toxic compound is the 2378-TeCDD. Currently, dioxins analysis can be done not only using GC-HRMS but also with GC-MS/MS according to European commission regulation (EU644/2017). Especially, GC-triple quadrupole MS is interesting in terms of handling, instrument size and operating costs. Recently, JEOL has developed a new GC-triple quadrupole MS (JMS-TQ4000GC) and a new dedicated dioxins analysis software called TQ-DioK. In this study, we evaluated JMS-TQ4000GC with TQ-DioK using dioxins standard samples. August 4, 2021 Application Note, GC Triple-Quad MS, Mass Spectrometry (MS) 0 Comment Read More >>
19F solid state NMR by using 2mmMAS probe_NM180013E JEOL 2mm MAS probe enables MA Spinning at nearly twice MAS speed of the conventional 3.2mm and 4mm MAS probe with 20 times the sample volume of the 1mm MAS probe. An attractive application of the 2mm MAS probe is 19F NMR. Strong 19F homonuclear dipolar coupling and wide chemical shift range cause a series of spinning side band (SSB) which make it difficult to analyze 19F spectra obtained by using the conventional 3.2mm and 4mm probes. The 2mm probe can achieve 40kHz MAS speeds, the resulting 19F spectra will had small well managed SSB’s. Here, we introduce 19F solid state NMR spectra of Nafion known as a solid polymer electrolyte for fuel cells. Fig.1 shows 19F MAS spectra of Nafion at various MAS speeds. 40kHz MAS gives a clear 19F spectrum without overlapping of SSBs whereas overlap occur between center bands and their SSBs at MAS speeds less than 40kHz. Moreover, the much greater sensitivity of the 2mm probe than the 1mm probe enables direct observation of low sensitive nuclei such as 13C. Thus, 13C{19F} CPMAS( Fig.2) and 13C-19F 2D-HETCOR (Fig.3) can easily be obtained. July 7, 2021 Nuclear Magnetic Resonance (NMR), Solid State NMR 0 Comment Read More >>
2mm HXMAS probe Multi-use probe capable of high speed MAS and high sensitivity measurements_NM210001E JEOL 2mm HXMAS probe is a multi-use probe capable of high speed magic angle spinning (MAS) up to 40kHz and high sensitivity measurements. It is not only available for general use in standard 13C measurements of organic materials, but also for highly sensitive 1H indirect detection utilizing high resolution 1H NMR. Since it is also suitable for 19F measurements where spinning side bands are likely to appear (JEOL application note: NM180013 ) and MQMAS measurements of quadrupole nucleus, the 2mm probe is strongly recommended probe that can handle a variety of measurements as a single probe. July 7, 2021 Nuclear Magnetic Resonance (NMR), Solid State NMR 0 Comment Read More >>