Kazuaki Fukushima

Quinolinic acid, α-picolinic acid, fusaric acid, and 2,6-pyridinedicarboxylic acid enhance the Fenton reaction in phosphate buffer ☆

Quinolinic acid, alpha-picolinic acid, fusaric acid, and 2,6-pyridinedicarboxylic acid enhanced the Fenton reaction in phosphate buffer, respectively. The enhancement by quinolinic acid, alpha-picolinic acid, fusaric acid, and 2,6-pyridinedicarboxylic acid of the Fenton reaction may be partly related to their respective actions in the biological systems such as a neurotoxic effect (quinolinic acid), a marked growth-inhibitory action on rice seeding (alpha-picolinic acid and fusaric acid), and an antiseptic (2,6-pyridinedicarboxylic acid). The ultraviolet-visible absorption spectrum of the mixture of alpha-picolinic acid with ferrous ion showed a characteristic visible absorbance band with a lambda(max) at 443 nm, suggesting that alpha-picolinic acid chelate of Fe2+ ion forms in the solution. Similar characteristic visible absorbance band was also observed for the mixture of Fe2+ ion with quinolinic acid (or fusaric acid, or 2,6-pyridinedicarboxylic acid). The chelation seems to be related to the enhancement by quinolinic acid, alpha-picolinic acid, fusaric acid, and 2,6-pyridinedicarboxylic acid of the Fenton reaction. alpha-Picolinic acid was reported to be a toxic substance isolated from the culture liquids of blast mould (Piricularia oryzae CAVARA). On the other hand, it has also been known that chlorogenic acid protects rice plants from the blast disease. The chlorogenic acid inhibited the formation of the hydroxyl radical in the reaction mixture of alpha-picolinic acid, FeSO4(NH4)2SO4, and H2O2. Thus the inhibition may be a possible mechanism of the protective action of the chlorogenic acid against the blast disease.

1∶1 Complex of guanine quartet with alkali metal cations detected by electrospray ionization mass spectrometry

Selective 1∶1 complex formation of a square quartet of 9-ethylguanine with small alkali metal cations (Li+, Na+) was detected by electrospray mass spectrometry

Effect of some naturally occurring iron ion chelators on the formation of radicals in the reaction mixtures of rat liver microsomes with ADP, Fe3+ and NADPH

In order to clarify the mechanism by polyphenols of protective effects against oxidative damage or by quinolinic acid of its neurotoxic and inflammatory actions, effects of polyphenols or quinolinic acid on the radical formation were examined. The ESR measurements showed that some polyphenols such as caffeic acid, catechol, gallic acid, D-(+)-catechin, L-dopa, chlorogenic acid and L-noradrenaline inhibited the formation of radicals in the reaction mixture of rat liver microsomes with ADP, Fe3+ and NADPH. The ESR measurements showed that α-picolinic acid, 2,6-pyridinedicarboxylic acid and quinolinic acid (2,3-pyridinedicarboxylic acid) enhanced the formation of radicals in the reaction mixture of rat liver microsomes with Fe3+ and NADPH. Caffeic acid and α-picolinic acid had no effects on the formation of radicals in the presence of EDTA, suggesting that the chelation of iron ion seems to be related to the inhibitory and enhanced effects. The polyphenols may exert protective effects against oxidative damage of erythrocyte membrane, ethanol-induced fatty livers, cardiovascular diseases, inflammatory and cancer through the mechanism. On the other hand, quinolinic acid may exert its neurotoxic and inflammatory effects because of the enhanced effect on the radical formation.

Effects of some naturally occurring iron ion chelators on in vitro superoxide radical formation.

The effects of some naturally occurring iron ion chelators and their derivatives on the electron transfer from ferrous ions to oxygen molecules were examined by measuring oxygen consumption rates. Of the compounds examined, quinolinic acid, fusaric acid, and 2-pyridinecarboxylic acid repressed the oxygen consumption, whereas chlorogenic acid, caffeic acid, gallic acid, catechol l-β-(3,4-dihydroxyphenyl) alanine, and xanthurenic acid accelerated it. Theoretical calculations showed that the energies of the highest occupied molecular orbitals (HOMOs) of [Fe(II)(ligand)3]− complexes were relatively high when the ligands were caffeic acid and its derivatives such as catechol, gallic acid, and l-β-(3,4-dihydroxyphenyl) alanine. On the other hand, the energies of the HOMOs of [Fe(II)(ligand)3]− complexes were relatively low when the ligands were quinolinic acid and its derivatives such as 2-pyridinecarboxylic acid and fusaric acid. The energies of the HOMOs appear to be closely related with acceleration or repression of the oxygen consumption; that is to say, when the energy of the HOMO is high, the oxygen consumption is accelerated, and vice versa.

High resolution, low hν photoelectron spectroscopy with the use of a microwave excited rare gas lamp and ionic crystal filters.

The need for not only bulk sensitive but also extremely high resolution photoelectron spectroscopy for studying detailed electronic structures of strongly correlated electron systems is growing rapidly. Moreover, easy access to such a capability in ones own laboratory is desirable. Demonstrated here is the performance of a microwave excited rare gas (Xe, Kr, and Ar) lamp combined with ionic crystal filters (sapphire, CaF(2), and LiF), which can supply three strong lines near the photon energy of hnyu hν=8.4, 10.0, and 11.6 eV, with the hν resolution of better than 600 μeV for photoelectron spectroscopy. Its performance is demonstrated on some materials by means of both angle-integrated and angle-resolved measurements.In view of the nonlinear and time-delay characteristics in acid and alkali neutral reaction process, a novel parameter self-adjusting Fuzzy-PID control method is proposed. The fuzzy controller can adjust PID controllers parameters online according to the real-time deviation of pH value. There are two main methods to obtain the expected control index. Firstly, through enhancing the sensitivity of the linguistic value, it can adapt the big change rate of pH value nearby the neutral point when the deviation is small. Secondly, by analyzing the magnitude and symbol of the deviation and change rate of deviation, fuzzy rules can be well established. The simulation results show that the method can not only adapt to the change of pH value in large scale, but also overcome the flow fluctuation.

Selective cation binding of crown ether acetals in electrospray ionization mass spectrometry

Diphenyl-substituted 11- to 20-membered ring crown ether acetals 1a–d exhibit selective cation complexation with alkali metal ions and NH4+ in electrospray ionization mass spectrometry (ESI-MS). In addition, cation-bound crown ether dimers (sandwiches) and trimers have also been observed, especially for the smaller crown ethers. However, their binding ability is completely lost upon acetal hydrolysis. It has been found that these crown ether acetals tend to preferentially bind smaller ions as compared with the corresponding simple crown ethers possessing the same number of ring oxygen atoms. These results are discussed on the basis of ring-contracted deformation, hydrophobic effects of the diphenyl group and the reduced solvation energies of the complexes.

Amine‐Urea‐Mediated Asymmetric Cycloadditions between Nitrile Oxides and o‐Hydroxystyrenes by Dual Activation

The first example of asymmetric 1,3-dipolar cycloadditions between nitrile oxides and o-hydroxystyrenes, mediated by cinchona-alkaloid-based amine-ureas is reported. The method is based on a dual activation involving both LUMO and HOMO activations. In addition to the stoichiometric asymmetric induction, a catalytic amount of amine-urea enables the cycloadditions to proceed in an enantioselective manner. Computational studies strongly support the HOMO activation of o-hydroxystyrenes and LUMO activation of nitrile oxides by hydrogen-bonding interactions with the Brønsted acid/base bifunctional catalyst.

Soft X-ray Angle Resolved Photoemission with Micro Positioning Techniques for Metallic V2O3

Soft X-ray micro-ARPES measurements have successfully been applied to band mapping of the strongly correlated metallic V2O3.

Soft x-ray angle-resolved and resonance photoemission study of CeCu2Ge2 and LaCu2Ge2

We have performed bulk-sensitive soft x-ray angle-resolved photoemission spectroscopy for CeCu2Ge2 isostructural to a heavy fermion superconductor CeCu2Si2, indicating the localized 4f character in ambient pressure. Resonance enhancement is seen at the La 3d5/2-edge for LaCu2Ge2 in both angle-resolved and integrated photoemission although the magnitude of enhancement is less than that in the Ce 3d5/2-edge resonance photoemission for CeCu2Ge2, which indicates that the rare-earth 5d contributions can also be enhanced in addition to the 4f contributions at the resonance conditions.

REGIO-SELECTIVITY AND RELATIVE REACTIVITY OF YLIDE FORMATION IN THE REACTION OF KETOCARBENOID WITH HETERO-CUMULENES

The regiochemistry of the reaction of ketocarbenoid with phenyl isocyanate, phenyl isothiocyanate, and phenyl isoselenocyanate was studied and relative reactivity of these heteromultiple compounds was determined by competitive reactions. The order of the reactivity and the regio-selectivity in the reactions are explained by molecular orbital calculation. Recently, a transition metal catalyzed reaction of diazo compounds with substrates having hetero atom has been accepted as a versatile method for ylide formation (1). Especially, the reaction of ketocarbenoid with hetero-multiple bond such as nitrile or carbon disulfide is the subject of much interest due to its potential role as a synthetic method for five-membered heterocycles such as oxazoles (2) and oxathiol-2-thione (3) through thermally allowed βπ-electron cyclization of acyl-substituted nitrile ylide and thiocarbonyl ylide intermediates, respectively.