Analytical Instrument Documents

The new generation diffusion probe is specially designed for diffusion applications that requires a large magnetic field gradient. By improving the design around the coil, the recovery time after field gradient pulse has been significantly shortened compared to the conventional model. Using a newly developed 50A bipolar magnetic field gradient power supply, a magnetic field gradient of 20 T/m (2000 G/cm) can be applied, making it possible to measure diffusion coefficients on the order of 10-14 m2/s. This system is ideal for measuring the diffusion of ions in solid electrolytes.

Catalyzed light olefin oligomerization is widely used in petrochemical industries to produce fuels and chemicals. Light olefins such as propene and butenes are commonly selected as feedstocks. Solid phosphoric acid (SPA) and zeolite are representative acidic catalysts. Both the feedstocks and catalysts have an impact on the product composition. In this study, state-of-the-art instrumentation two-dimensional gas chromatography (GC × GC) coupled photoionization─time of flight mass spectrometry was employed to investigate the composition of dodecene products produced from olefin oligomerization. Information such as the olefin congener distribution, dodecene structural subgroup distribution, and individual dodecene isomers was obtained and utilized in the statistical analyses. By using specific data sets of the product composition, the distinguishment between SPA and zeolite catalysts as well as among the feedstocks was achieved by applying the unsupervised screening approaches (principal component analysis and hierarchical clustering analysis). The potential indicators of catalysts and feedstocks were selected by the feature selection methods (univariate analysis: analysis of variance and multivariate analysis: partial least squares-discriminant analysis).

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.

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 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.

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.

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.

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.

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.

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.