K. Takegoshi

Kyoto University, Kioto, Kyōto, Japan

Are you K. Takegoshi?

Claim your profile

Publications (163)577.59 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Even though microcoils improve the sensitivity of NMR measurement of tiny samples, magnetic-filed 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. In addition, the paramagnetic liquid serves as coolant when it is circulated through the copper capillary, effectively transferring the heat generated by radiofrequency pulses.
  • [Show abstract] [Hide abstract]
    ABSTRACT: A 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. Hence the angle between the spinner axis and the effective magnetic field can be controlled by current I supplied to the X0 shim coil, leading to precise angle adjustment without backlash accompanied with a mechanical system conventionally used. It is shown that the angle range achieved is ±0.05° for I=±5A at B0=7T. Copyright © 2015 Elsevier Inc. All rights reserved.
    Journal of Magnetic Resonance 04/2015; 182. DOI:10.1016/j.jmr.2015.04.007 · 2.32 Impact Factor
  • Macromolecules 02/2015; 48(3):629-636. DOI:10.1021/ma502165u · 5.93 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The 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. E. Bennett, C. M. Rienstra, M. Auger, K. V. Lakshmi, and R. G. Griffin, J. Chem. Phys. 103, 6951-6958 (1995) and I. Scholz, P. Hodgkinson, B. H. Meier, and M. Ernst, J. Chem. Phys. 130, 114510 (2009)] are discussed. The structure of recoupling bands caused by interference of the (1)H spin nutation with sample spinning is studied by both experiments and numerical simulations.
    The Journal of Chemical Physics 12/2014; 141(22):224202. DOI:10.1063/1.4903173 · 3.12 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Proton multiple-quantum (MQ) spin-counting experiment has been employed to study arrangement of hydrogen atoms in 9 Å/11 Å natural/synthetic tobermorites. Even though all tobermorite samples give similar characterless, broad static-powder 1H NMR spectra, their MQ spin-counting spectra are markedly different; higher quanta in 11 Å tobermorite do not grow with the MQ excitation time, while those in 9 Å one do. A statistical analysis of the MQ results recently proposed [26] is applied to show that hydrogens align in 9 Å tobermorite one dimensionally, while in 11 Å tobermorite they exist as a cluster of 5–8 hydrogen atoms.
    Cement and Concrete Research 12/2014; 66:115–120. DOI:10.1016/j.cemconres.2014.07.023 · 3.85 Impact Factor
  • Naoki Ichijo, Kazuyuki Takeda, K. Takegoshi
    [Show abstract] [Hide abstract]
    ABSTRACT: We 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, 4.0, and 5.4T at a fixed carrier frequency of 56.0MHz. Since both the main-field inhomogeneity and the paramagnetic magnetization are proportional to the main-magnet current, the resonance lines are equally narrowed by the improved field homogeneity with an identical configuration of the paramagnetic shim pieces. Paramagnetic shimming presented in this work opens the possibility of high-resolution variable-field NMR experiments.
    Journal of Magnetic Resonance 09/2014; 246. DOI:10.1016/j.jmr.2014.06.022 · 2.32 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We 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.
    Journal of Magnetic Resonance 08/2014; 245. DOI:10.1016/j.jmr.2014.06.003 · 2.32 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Lithium overstoichiometric LixCoO2 (x > 1) with few phase transitions is promising as a positive electrode material for lithium ion batteries; however, the detailed lithium local structures around excess Li ions remain unknown and need to be elucidated. It has been postulated that the excess Li ion occupies the Co site, and the resulting charge deficit is compensated for by oxygen vacancies and the valence of Co. Two spin states have been invoked for the Co ion; one is Co3+ taking an intermediate spin state (S = 1) and the other is low spin Co2+ (S = 1/2). The paramagnetic shift caused by the Co spin is appreciable by 6/7Li nuclear magnetic resonance (NMR) in solids using magic-angle spinning (MAS), and we show that there are five “major” minor signals at ca. −16, −6, 3, 185, and 1100 ppm with the intensity ratio of 2:4:4:2:0.5-1.0, in addition to the major signal at 0 ppm. Analysis of temperature-dependent 7Li shifts and also 6Li T1 experiments confirm that the observed shifts for these minor peaks are ascribed to the paramagnetic interaction. To examine distance proximities among these lithium ions at the minor sites, we apply three 7Li-7Li two-dimensional (2D) correlation experiments and show that the three minor lithium atoms, whose shifts are 3, −6, and −16 ppm, exist in the same Li layer. Further, from rotational-resonance recoupling experiment, it is indicated that the lithium appearing at −16 ppm is closest to that at ca. 185 ppm. Based on these results, we show that a defect structure assuming low spin Co2+ which is not associated with the oxygen vacancy is consistent with the NMR results. This leads us to invoke Li insertion at an interstitial site, which has been negated, for the position of the excess Li atom.
    The Journal of Physical Chemistry C 07/2014; 118(28):15375-15385. DOI:10.1021/jp5039909 · 4.84 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Pradimicins (PRMs) and benanomicins are the only family of non-peptidic natural products with lectin-like properties, that is, they recognize D-mannopyranoside (Man) in the presence of Ca(2+) ions. Coupled with their unique Man binding ability, they exhibit antifungal and anti-HIV activities through binding to Man-containing glycans of pathogens. Notwithstanding the great potential of PRMs as the lectin mimics and therapeutic leads, their molecular basis of Man recognition has yet to be established. Their aggregate-forming propensity has impeded conventional interaction analysis in solution, and the analytical difficulty is exacerbated by the existence of two Man binding sites in PRMs. In this work, we investigated the geometry of the primary Man binding of PRM-A, an original member of PRMs, by the recently developed analytical strategy using the solid aggregate composed of the 1:1 complex of PRM-A and Man. Evaluation of intermolecular distances by solid-state NMR spectroscopy revealed that the C2-C4 region of Man is in close contact with the primary binding site of PRM-A, while the C1 and C6 positions of Man are relatively distant. The binding geometry was further validated by co-precipitation experiments using deoxy-Man derivatives, leading to the proposal that PRM-A binds not only to terminal Man residues at the non-reducing end of glycans, but also to internal 6-substituted Man residues. The present study provides new insights into the molecular basis of Man recognition and glycan specificity of PRM-A.
    Chemistry - A European Journal 08/2013; 19(32). DOI:10.1002/chem.201301368 · 5.70 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: 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. The second regime, νR<Δνiso(max), can be used to observe long-range constraints with lower spinning speed, which increases the transfer efficiency, and may allow using bigger rotors to increase the S/N ratio.
    Solid State Nuclear Magnetic Resonance 08/2013; 55-56. DOI:10.1016/j.ssnmr.2013.07.001 · 2.86 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The aggregation of 42-residue amyloid β-protein (Aβ42) is involved in the pathogenesis of Alzheimer's disease (AD). Numerous flavonoids exhibit inhibitory activity against Aβ42 aggregation, but their mechanism remains unclear in molecular level. Here we propose the site-specific inhibitory mechanism of (+)-taxifolin, a catechol-type flavonoid, whose 3',4'-dihydroxyl groups of the B-ring plays a critical role. Addition of sodium periodate, an oxidant, strengthened suppression of Aβ42 aggregation by (+)-taxifolin, whereas no inhibition was observed under anaerobic conditions, suggesting the inhibition to be associated with the oxidation to form o-quinone. Since the formation of Aβ42-taxifolin adduct was suggested by mass spectrometry, Aβ42 mutants substituted at Arg5, Lys16, and/or Lys28 with norleucine (nL) were prepared to identify the residues involved in the conjugate formation. (+)-Taxifolin did not suppress the aggregation of Aβ42 mutants at Lys16 and/or Lys28 except for the mutant at Arg5. In addition, the aggregation of Aβ42 was inhibited by other catechol-type flavonoids, while that of K16nL-Aβ42 was not. In contrast, some non-catechol-type flavonoids suppressed the aggregation of K16nL-Aβ42 as well as Aβ42. Furthermore, interaction of (+)-taxifolin with β-sheet in Aβ42 was not observed using solid-state NMR unlike curcumin of non-catechol-type. These results demonstrate that catechol-type flavonoids could specifically suppress Aβ42 aggregation by targeting Lys-residues. Although the anti-AD activity of flavonoids has been ascribed to their anti-oxidative activity, the mechanism that the o-quinone reacts with Lys-residues of Aβ42 might be more intrinsic. The Lys-residues could be targets for Alzheimer's therapy.
    Journal of Biological Chemistry 06/2013; DOI:10.1074/jbc.M113.464222 · 4.60 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A novel statistical approach for analyzing (1)H multiple-quantum (MQ) spin dynamics in so-called spin-counting solid-state NMR experiments is presented. The statistical approach is based on the percolation theory with Monte Carlo methods and is examined by applying it to the experimental results of three solid samples having unique hydrogen arrangement for 1-3 dimensions: the n-alkane/d-urea inclusion complex as a one-dimensional (1D) system, whose (1)H nuclei align approximately in 1D, and magnesium hydroxide and adamantane as a two-dimensional (2D) and a three-dimensional (3D) system, respectively. Four lattice models, linear, honeycomb, square and cubic, are used to represent the (1)H arrangement of the three samples. It is shown that the MQ dynamics in adamantane is consistent with that calculated using the cubic lattice and that in Mg(OH)2 with that calculated using the honeycomb and the square lattices. For n-C20H42/d-urea, these 4 lattice models fail to express its result. It is shown that a more realistic model representing the (1)H arrangement of n-C20H42/d-urea can describe the result. The present approach can thus be used to determine (1)H arrangement in solids.
    Physical Chemistry Chemical Physics 04/2013; 15(19). DOI:10.1039/c3cp43778g · 4.20 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: I still see you: A new pulse sequence, SHA+, little sensitive to dipolar truncation, allows direct or relayed polarization transfer between (13) C atoms, distant by 3.5-9.6 Å, in amyloid fibrils. SHA+ can also be used in a broadband way with the weak rf-condition of ν(1) /ν(R) ≈0.2-0.3 which permits the investigation of temperature-sensitive biological systems.
    ChemPhysChem 11/2012; 13(16). DOI:10.1002/cphc.201200548 · 3.36 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Alzheimer's disease (AD) is caused by abnormal deposition (fibrillation) of a 42-residue amyloid β-protein (Aβ42) in the brain. During the process of fibrillation, the Aβ42 takes the form of protofibrils with strong neurotoxicity, and is thus believed to play a crucial role in the pathogenesis of AD. To elucidate the supramolecular structure of the Aβ42 protofibrils, the intermolecular proximity of the Ala-21 residues in the Aβ42 protofibrils was analyzed by (13)C-(13)C rotational resonance experiments in the solid state. Unlike the Aβ42 fibrils, an intermolecular (13)C-(13)C correlation was not found in the Aβ42 protofibrils. This result suggests that the β-strands of the Aβ42 protofibrils are not in an in-register parallel orientation. Aβ42 monomers would assemble to form protofibrils with the β-strand conformation, then transform into fibrils by forming intermolecular parallel β-sheets.
    Biochemical and Biophysical Research Communications 11/2012; 428(4). DOI:10.1016/j.bbrc.2012.10.096 · 2.28 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We explore the possibility for elemental analysis by NMR. To keep the efficiency of the signal acquisition common for all spin species, we propose to fix the frequency and vary the magnetic field to cover the isotopes involved in a sample. We introduce constant-frequency receptivity for quantitative elemental analysis in the frequency-fixed NMR experiment. Field-variable NMR experiments are demonstrated using a cryogen-free superconducting magnet. In addition to elemental analysis in liquid solution, solid-state NMR under magic-angle spinning is also described.
    Journal of Magnetic Resonance 09/2012; 224:48-52. DOI:10.1016/j.jmr.2012.09.004 · 2.32 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Two-dimensional (2D) covariance NMR spectroscopy, which has originally been established to extract homonuclear correlations (HOMCOR), is extended to include heteronuclear correlations (HETCOR). In a (13)C/(15)N 2D chemical shift correlation experiment, (13)C and (15)N signals of a polycrystalline sample of (13)C, (15)N-labeled amino acid are acquired simultaneously using a dual-receiver NMR system. The data sets are rearranged for the covariance data processing, and the (13)C-(15)N heteronuclear correlations are obtained together with the (13)C-(13)C and (15)N-(15)N homonuclear correlations. The present approach retains the favorable feature of the original covariance HOMCOR that the spectral resolution along the indirect dimension is given by that of the detection dimension. As a result, much fewer amounts of data are required to obtain a well-resolved 2D spectrum compared to the case of the conventional 2D Fourier-Transformation (FT) scheme. Hence, one can significantly save the experimental time, or enhance the sensitivity by increasing the number of signal averaging within a given measurement time.
    Physical Chemistry Chemical Physics 06/2012; 14(27):9715-21. DOI:10.1039/c2cp41191a · 4.20 Impact Factor
  • Source
    Konstantin I Momot, K Takegoshi
    [Show abstract] [Hide abstract]
    ABSTRACT: We present a formalism for the analysis of sensitivity of nuclear magnetic resonance pulse sequences to variations of pulse sequence parameters, such as radiofrequency pulses, gradient pulses or evolution delays. The formalism enables the calculation of compact, analytic expressions for the derivatives of the density matrix and the observed signal with respect to the parameters varied. The analysis is based on two constructs computed in the course of modified density-matrix simulations: the error interrogation operators and error commutators. The approach presented is consequently named the Error Commutator Formalism (ECF). It is used to evaluate the sensitivity of the density matrix to parameter variation based on the simulations carried out for the ideal parameters, obviating the need for finite-difference calculations of signal errors. The ECF analysis therefore carries a computational cost comparable to a single density-matrix or product-operator simulation. Its application is illustrated using a number of examples from basic NMR spectroscopy. We show that the strength of the ECF is its ability to provide analytic insights into the propagation of errors through pulse sequences and the behaviour of signal errors under phase cycling. Furthermore, the approach is algorithmic and easily amenable to implementation in the form of a programming code. It is envisaged that it could be incorporated into standard NMR product-operator simulation packages.
    Journal of Magnetic Resonance 05/2012; 221:57-68. DOI:10.1016/j.jmr.2012.05.004 · 2.32 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In oxides, the substitution of non-oxide anions (F(-),S(2-),N(3-) and so on) for oxide introduces many properties, but the least commonly encountered substitution is where the hydride anion (H(-)) replaces oxygen to form an oxyhydride. Only a handful of oxyhydrides have been reported, mainly with electropositive main group elements or as layered cobalt oxides with unusually low oxidation states. Here, we present an oxyhydride of the perhaps most well-known perovskite, BaTiO(3), as an O(2-)/H(-) solid solution with hydride concentrations up to 20% of the anion sites. BaTiO(3-x)H(x) is electronically conducting, and stable in air and water at ambient conditions. Furthermore, the hydride species is exchangeable with hydrogen gas at 400 °C. Such an exchange implies diffusion of hydride, and interesting diffusion mechanisms specific to hydrogen may be at play. Moreover, such a labile anion in an oxide framework should be useful in further expanding the mixed-anion chemistry of the solid state.
    Nature Material 04/2012; 11(6):507-11. DOI:10.1038/nmat3302 · 36.43 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Pradimicin A (PRM-A) is a unique antibiotic with a lectin-like ability to recognize d-mannopyranosides (Man) in the presence of Ca(2+) ion. BMY-28864 (1) is a water-soluble analogue of PRM-A, which has been extensively used for studies on the mode of Man recognition and antifungal action of pradimicins. Although it has been assumed that PRM-A and 1 bind Man in a similar fashion, direct experimental evidence has yet to be provided. In this report, we compared Ca(2+) and Man binding of 1 with that of PRM-A through two solid-state NMR experiments. The solid-state (113)Cd NMR analysis using (113)Cd(2+) ion as a surrogate for Ca(2+) ion suggested the similarity in Ca(2+) coordination of PRM-A and 1. The dipolar assisted rotational resonance (DARR) analysis using (13)C-labeled 1 clearly showed that 1 as well as PRM-A binds Man near its carboxyl group. These results collectively indicate that the mode of binding of Ca(2+) ion and Man is nearly identical between PRM-A and 1.
    Bioorganic & medicinal chemistry letters 12/2011; 22(2):1040-3. DOI:10.1016/j.bmcl.2011.11.106 · 2.33 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We study the QUantitative Cross-Polarization (QU-CP) method proposed by Hou et al. (Chem. Phys. Lett. 421 (2006) 356) under the moderate MAS speed of 23 kHz, re-examining its two building blocks, namely, the CP polarization transfer from (1)H to (13)C, and the thermal equalization of the (13)C magnetizations. We show that the nuclear-integrated cross-polarization (NI-CP) scheme is conveniently used for (1)H-(13)C polarization transfer, because of its simplicity, robustness to rf-mismatch, and compatibility with fast sample spinning. In the mixing part, in addition to dipolar-assisted rotational-resonance (DARR) recoupling, we examine the Phase-Alternated Recoupling Irradiation Schemes (PARIS and PARIS(xy)), and Second-order Hamiltonian among Analogous Nuclei Generated by Hetero-nuclear Assistance Irradiation (SHANGHAI) sequences, and show that SHANGHAI gives the best performances in equalizing the (13)C magnetizations.
    Journal of Magnetic Resonance 11/2011; 214(1):340-5. DOI:10.1016/j.jmr.2011.11.014 · 2.32 Impact Factor

Publication Stats

2k Citations
577.59 Total Impact Points

Institutions

  • 1982–2015
    • Kyoto University
      • • Division of Chemistry
      • • Department of Energy and Hydrocarbon Chemistry
      Kioto, Kyōto, Japan
  • 2004
    • National Institute of Agrobiological Sciences
      Tsukuba, Ibaraki, Japan
  • 1989–1999
    • Hokkaido University
      • • Division of Biological Sciences (Biology)
      • • Faculty of Science
      Sapporo, Hokkaidō, Japan
  • 1996
    • Mie University
      Tu, Mie, Japan
  • 1989–1990
    • University of California, Berkeley
      • • Department of Chemistry
      • • Lawrence Berkeley Laboratory
      Berkeley, California, United States
  • 1985–1988
    • University of British Columbia - Vancouver
      • Department of Chemistry
      Vancouver, British Columbia, Canada