Nuclear Quadrupole Resonance (NQR) provides spectra carrying information as to the electric-field gradient around nuclei with a spin quantum number I > 1/2 and offers helpful clues toward characterizing the electronic structure of materials of chemical interest. A major challenge in NQR is finding hitherto unknown resonance frequencies, which can scatter over a wide range, requiring time consuming repetitive measurements with stepwise frequency increments. Here, we report on an efficient, two-step NQR protocol by bringing rapid-scan and frequency-comb together.
View Article and Find Full Text PDFThe effects of substituents and solvents on the NH tautomerism of N-confused porphyrin () were investigated. The structures, electronic states, and aromaticity of NH tautomers ( and ) were studied by absorption and nuclear magnetic resonance (H, C, and N) spectroscopies, single-crystal X-ray diffraction analysis, and theoretical calculations. The relative stability of the tautomers is highly affected by solvents, with the -type tautomer being more stable in nonpolar solvents, while the -type tautomer being highly stabilized in polar solvents with high donor numbers such as ,-dimethylformamide (DMF), pyridine, and acetone.
View Article and Find Full Text PDFLigand molecules capping on clusters largely affect the formation and stabilization mechanism and the property of clusters. In semiconductor CdSe clusters, cysteine is used as one of the ligands and allows the formation of ultrastable (CdSe) magic-sized clusters. Cysteine has sulfhydryl, amine, and carboxylate groups, all of which have coordination ability to the CdSe surface, and the bonding states of the three functional groups of ligand-cysteine on the CdSe core have not been determined.
View Article and Find Full Text PDFSolid State Nucl Magn Reson
September 2019
To examine bonding nature of fluorine ligands in a metal coordinated system, F high-resolution solid-state NMR has been applied to TiF, which bears both bridging and terminal fluorines. Observed 12 isotropic signals are assigned to 12 crystallographically different fluorines (6 terminal and 6 bridging fluorines) in TiF by referring to the calculated isotropic shifts using density functional theory (DFT). The isotropic chemical shift (δ) for terminal F (F) appears at high frequency (420-480 ppm from δ(CClF) = 0 ppm) with large shielding anisotropy Δσ ∼ 850 ppm.
View Article and Find Full Text PDFNaturally occurring pradimicins (PRMs) show specific recognition of d-mannose (d-Man) in aqueous media, which has never been achieved by artificial small molecules. Although the Ca-mediated dimerization of PRMs is essential for their d-Man binding, the dimeric structure has yet to be elucidated, leaving the question open as to how PRMs recognize d-Man. Thus, we herein report the structural elucidation of the dimer by a combination of X-ray crystallography and solid-state NMR spectroscopy.
View Article and Find Full Text PDFWe propose a variant of covariance NMR spectroscopy, namely, inner-product NMR spectroscopy, originally suggested in Takeda (2015). The mathematical operation of inner-product NMR is the same as that of covariance NMR, except that subtraction of the average value of the variable is intentionally omitted, so that the correspondence of the spectrum with that of conventional two-dimensional Fourier-transformation is established without having to request the average to become vanishingly small. We demonstrate inner-product NMR for C DARR correlation experiments in a polycrystalline sample of C-labeled l-alanine.
View Article and Find Full Text PDFSphingosine-1-phospate is a potent bioactive lipid metabolite that regulates cancer progression. Because sphingosine kinase 1 and sphingosine kinase 2 (SPHK 1/2) are both essential for sphingosine-1-phospate production, they could be a therapeutic target in various cancers. Peretinoin, an acyclic retinoid, inhibits post-therapeutic recurrence of hepatocellular carcinoma via unclear mechanisms.
View Article and Find Full Text PDFA 59-year-old man was admitted to the hospital with acute pancreatitis. The cause was suggested to be a pancreatic tumor based on computed tomography (CT). The pancreatic tumor was 45 mm with an extensive tumor embolism at the trunk of the portal vein and intraductal infiltration of the main pancreatic duct (MPD).
View Article and Find Full Text PDFThe pathogenesis of non-alcoholic steatohepatitis (NASH) is still unclear and the prevention of the development of hepatocellular carcinoma (HCC) has not been established. We established an atherogenic and high-fat diet mouse model that develops hepatic steatosis, inflammation, fibrosis, and liver tumors at a high frequency. Using two NASH-HCC mouse models, we showed that peretinoin, an acyclic retinoid, significantly improved liver histology and reduced the incidence of liver tumors.
View Article and Find Full Text PDFLigand-surface interaction of semiconductor nanoparticles (NPs) controls their optoelectronic properties, and thus examination of the interaction is essential for the nanoelectronic applications of NPs. Herein, solid-state nuclear magnetic resonance (NMR) is performed to unravel the ligand-surface interaction in cysteine-capped CdSe magic-sized clusters. N-Cd through-bond J-filtered NMR directly shows the presence of the nitrogen-cadmium chemical bond for the first time and indicates that ∼43% of the amines form the chemical bond.
View Article and Find Full Text PDFRotational resonance (R2) is one of the widely applied techniques in solid-state NMR for recoupling a homonuclear dipolar interaction under magic-angle spinning (MAS). R2 occurs as the result of interference between the difference of the chemical shifts and MAS. In this work, we extend R2 to a heteronuclear dipolar interaction in the interaction frame of RF irradiation.
View Article and Find Full Text PDFOral supplementation with branched-chain amino acids (BCAA; leucine, isoleucine, and valine) in patients with liver cirrhosis potentially suppresses the incidence of hepatocellular carcinoma (HCC) and improves event-free survival. However, the detailed mechanisms of BCAA action have not been fully elucidated. BCAA were administered to atherogenic and high-fat (Ath+HF) diet-induced nonalcoholic steatohepatitis (NASH) model mice.
View Article and Find Full Text PDFPradimicin A (PRM-A) is a unique natural product that recognizes d-mannopyranoside (Man) in the presence of Ca ion. Although the Man binding geometry of PRM-A is largely understood, the molecular basis of Man recognition has yet to be established because of the lack of information regarding Ca binding geometry. In this work, to examine the Ca binding site of PRM-A, we performed a solid-state nuclear magnetic resonance experiment using Cd as a surrogate probe for Ca.
View Article and Find Full Text PDFThe double-acquisition scheme for efficient data collection of hypercomplex data (the States method) of a two-dimensional experiment is adopted to magic-angle hopping (MAH) and magic-angle turning (MAT) experiments, which are powerful methods to measure the principal values of the chemical shift anisotropy (CSA) in a powder sample. It is shown that the double acquisition MAT (DAMAT) sequence realizes the S/N ratio comparable to or better than those of other variants of the MAH/MAT sequences. In addition, we show that DAMAT has preferable features that there are no spinning sidebands in the indirect dimension, and no spectral shearing is necessary.
View Article and Find Full Text PDFWe propose a simple data-analysis scheme to determine the coupling constant and the asymmetry parameter of nuclear quadrupolar interactions in field-swept nuclear magnetic resonance (NMR) for static powder samples. This approach correlates the quadrupolar parameters to the positions of the singularities, which can readily be found out as sharp peaks in the field-swept pattern. Moreover, the parameters can be determined without quantitative acquisition and elaborate calculation of the overall profile of the pattern.
View Article and Find Full Text PDFIn synthesizing mixed anion oxides, direct syntheses have often been employed, usually involving high temperature and occasionally high pressure. Compared with these methods, here we show how the use of a titanium perovskite oxyhydride (BaTiO2.5H0.
View Article and Find Full Text PDFEven though microcoils improve the sensitivity of NMR measurement of tiny samples, magnetic-field inhomogeneity due to the bulk susceptibility effect of the coil material can cause serious resonance-line broadening. Here, we propose to fabricate the microcoil using a thin, hollow copper capillary instead of a wire and fill paramagnetic liquid inside the capillary, so as to cancel the diamagnetic contribution of the copper. Susceptibility cancellation is demonstrated using aqueous solution of NiSO4.
View Article and Find Full Text PDFDifferentially regulated microRNA (miRNA) are associated with hepatic fibrosis; however, their potential usefulness for blocking hepatic fibrosis has not been exploited fully. We examined the expression of miRNA in the liver of a transgenic mouse model in which platelet-derived growth factor C (PDGF-C) is overexpressed (Pdgf-c Tg), resulting in hepatic fibrosis and steatosis and the eventual development of hepatocellular carcinoma (HCC). Robust induction of miR-214 correlated with fibrogenesis in the liver of Pdgf-c Tg mice, atherogenic high-fat diet-induced NASH mice, and patients with chronic hepatitis B or C.
View Article and Find Full Text PDFA new method for precise setting of the spinning angle to the magic angle by using a saddle coil is described. The coil, which is referred to as an X0 shim coil, is wound to produce a uniform static magnetic field Bx perpendicular to the main magnetic field B0. The magnetic field felt by a sample is a vector sum of the main field B0 and the transverse field Bx produced by the X0 shim coil.
View Article and Find Full Text PDFWe here revisit expansion schemes used in nuclear magnetic resonance (NMR) for the calculation of effective Hamiltonians and propagators, namely, Magnus, Floquet, and Fer expansions. While all the expansion schemes are powerful methods there are subtle differences among them. To understand the differences, we performed explicit calculation for heteronuclear dipolar decoupling, cross-polarization, and rotary-resonance experiments in solid-state NMR.
View Article and Find Full Text PDFThe effect of (1)H decoupling in magic-angle spinning solid-state NMR is studied under radiofrequency irradiation causing simultaneous nutations around a pair of orthogonal axes. Double-nutation with an arbitrary pair of nutation frequencies is implemented through modulation of the amplitude, phase, and frequency of the transmitting pulses. Similarity and difference of double-nutation decoupling and two-pulse phase-modulation decoupling schemes [A.
View Article and Find Full Text PDFWe propose a new passive shimming strategy for variable-field NMR experiments, in which the magnetic field produced by paramagnetic shim pieces placed inside the magnet bore compensates the inhomogeneity of a variable-field magnet for a wide range of magnet currents. Paramagnetic shimming is demonstrated in (7)Li, (87)Rb, and (45)Sc NMR of a liquid solution sample in magnetic fields of 3.4, 4.
View Article and Find Full Text PDFWe propose a cross polarization (CP) sequence effective under magic-angle spinning (MAS) which is tolerant to RF field inhomogeneity and Hartmann-Hahn mismatch. Its key feature is that spin locking is not used, as CP occurs among the longitudinal (Z) magnetizations modulated by the combination of two pulses with the opposite phases. We show that, by changing the phases of the pulse pairs synchronized with MAS, the flip-flop term of the dipolar interaction is restored under MAS.
View Article and Find Full Text PDFSolid State Nucl Magn Reson
June 2014
We explore modulation-sideband recoupling conditions of the (13)C-(13)C Second-order Hamiltonian among Analogous nuclei plus pulse sequence (SHA+), and found that this sequence can be used in two different recoupling regimes. The first regime, νR>Δνiso(max), is recommended for broad-band recoupling to avoid any rotational resonance broadening. In this regime, the spinning speed should be only slightly larger than Δνiso(max), to obtain the best transfer efficiency.
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