Biomedical subjects

Midori Goto

Publications and source records attributed to Midori Goto.

10 recordsLinked to original sources

PubMed2007

Temporally regulated asymmetric neurogenesis causes left-right difference in the zebrafish habenular structures.

The habenular neurons on both sides of the zebrafish diencephalon show an asymmetric (laterotopic) axonal projection pattern into the interpeduncular nucleus. We previously revealed that the habenula could be subdivided into medial and lateral subnuclei, and a prominent left-right difference in the size ratio of these subnuclei accounts for the asymmetry in its neural connectivity. In the present study, birth date analysis showed that neural precursors for the lateral subnuclei were born at earlier stages than those for the medial subnuclei. More neurons for the early-born lateral subnuclei were generated on the left side, while more neurons for the late-born medial subnuclei were generated on the right side. Genetic hyperactivation and repression of Notch signaling revealed that differential timing determines both specificity and asymmetry in the neurogenesis of neural precursors for the habenular subnuclei.

Animals↗

PubMed2006

Fluorescence spectroscopic properties and crystal structure of a series of donor-acceptor diphenylpolyenes.

A series of p-nitro-p'-alkoxy(OR)-substituted (E,E,E)-1,6-diphenyl-1,3,5-hexatrienes (1a, R = Me; 1b, R = Et; 1c, R = n-Pr; 1d, R = n-Bu) were prepared. The absorption and fluorescence spectra in solution were almost independent of the alkoxy chain length. The absorption maximum showed only a small dependence on the solvent polarity, whereas the fluorescence maximum red-shifted largely as the polarity increased. The solid-state absorption and fluorescence spectra were red-shifted relative to those in low polar solvents and were clearly dependent on the alkoxy chain length. The fluorescence maxima for the crystals of 1b and 1d were observed at 635-650 nm, which were red-shifted by 40-50 nm relative to those for 1a and 1c. The Stokes shifts were all relatively small (3000-3500 cm-1). For all four compounds, the fluorescence decay curves in the solid state were able to be analyzed by single-exponential fitting to give the lifetimes of 1.1-1.3 ns. This indicates that the emission of 1a-d is not originated from an excimer or molecular aggregates, but from only one emitting monomeric species. The fluorescence quantum yields of 1a-d were considerably high compared with the values for organic solids, which is consistent with their monomeric origin of emission. Single-crystal X-ray structure analyses of 1a, 1c, and 1d showed that the crystal packing was dependent on the alkoxy chain length. The crystals of 1a and 1c had herringbone structure, whereas that of 1d had pi-stacked structure. Strong pi-pi interaction in the crystal of 1d would be the cause of the spectral red shifts relative to those for 1a and 1c. No observation of excimer fluorescence from crystal 1d can be attributed to the limited overlap between the pi-planes of the molecules due to its "slipped-parallel" structure.

Journal Article↗

PubMed2006

Synthesis of a [2]rotaxane incorporating a Ni(II)-salen moiety: evidence of ring-opening-and-closing protocol.

[reaction: see text] We have synthesized a [2]rotaxane from a crown-ether-like macrocycle that undergoes ring opening and closing through cleavage and formation of imino bonds of a salen moiety; the self-assembly of this macrocycle and a dumbbell-shaped rodlike component, followed by addition of nickel acetate, afforded, after counterion exchange, a [2]rotaxane that is stabilized through coordination of the Ni ion to the macrocycle's salen moiety.

Journal Article↗

PubMed2005

Crystalline-state Z,E-photoisomerization of a series of (Z,E,Z)-1,6-diphenylhexa-1,3,5-triene 4,4'-dicarboxylic acid dialkyl esters. Chain length effects on the crystal structure and photoreactivity.

[reaction: see text] Crystalline-state Z,E-photoisomerization of a series of (Z,E,Z)-1,6-diphenylhexa-1,3,5-triene 4,4'-dicarboxylic acid dialkyl (R) esters [(Z,E,Z)-1a, R = Me; (Z,E,Z)-1b, R = Et; (Z,E,Z)-1c, R = n-Pr; (Z,E,Z)-1d, R = n-Bu] was investigated. All Z,E,Z isomers underwent one-way isomerization to the corresponding E,E,E isomers. The reaction efficiency was strongly enhanced as the length of the alkyl chain increased. Single-crystal X-ray analyses of (Z,E,Z)-1a-d showed that the alkyl chain part of the crystals became larger as the chain length increased. The conformational flexibility of the alkyl chains made the large change in the triene geometry in the lattice possible, leading to the enhancement of the photoreactivity in the crystalline state.

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PubMed2004

STM observation of alkyl-chain-assisted self-assembled monolayers of pyridine-coordinated porphyrin rhodium chlorides.

Alkyl-chain-assisted self-assembled monolayers of pyridine-coordinated porphyrin rhodium chlorides were observed at the solid-liquid interface by scanning tunneling microscopy (STM). The resolved images at a molecular level were obtainable in the pure solution of pyridine-coordinated porphyrin rhodium chloride with four triacontyl groups [Rh(C300PP)(Cl)(Py)]. In the case of pyridine-coordinated porphyrin rhodium chloride with four octadecyl groups [Rh(C18OPP)(Cl)(Py)], the STM images were not obtainable in the pure solution of Rh(C18OPP)(Cl)(Py) but obtainable in the mixture containing Rh(C18OPP)(Cl)(Py) and free porphyrin C18OPP. On the basis of the mixed self-assembled monolayer analysis, the apparent difference in the adsorption free energy between Rh(CnOPP)(Cl)(Py) and CnOPP (deltaGapp) was calculated. The calculated deltaGapp values for C18OPP and C30OPP mixed systems were quite different. The disadvantage of the adsorption free energy of Rh(C18OPP)(Cl)(Py) makes it difficult to obtain molecularly resolved images of Rh(C18OPP)(Cl)(Py), and the large adsorption energy due to the long alkyl chains enabled us to obtain molecularly resolved images of Rh(C30OPP)(Cl)(Py).

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PubMed2004

Synthesis and characterisation of macrocyclic palladium(II)-sodium(I) complexes: generation of an unusual metal-mediated electron delocalisation.

Reaction of sodium perchlorate-crown ether derivative (LH2) complex [Na2LH2](ClO4)2 (1) with palladium acetate afforded two related compounds of macrocyclic palladium(II)-sodium(I) dimeric tetranuclear complexes, [Pd2Na2L2(mu-OH2)2](ClO4)2(CH2Cl2)3 (2) and [Pd2Na2(L-)2](CH3CN)2(C3H6O)2 (3) and their structures were characterised by IR, NMR, mass and X-ray analysis; the latter was revealed as an unusual metal-mediated electron delocalised complex.

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PubMed2003

Hexaaquairon(II) dipicrate dihydrate.

In the crystal structure of the title compound, [Fe(H(2)O)(6)](C(6)H(2)N(3)O(7))(2).2H(2)O, the centrosymmetric cationic iron complexes and picrate anions form separate stacks extending along the b axis. No picrate species ligate to the metal cation. Picrate ions are linked to one another in the stack via short intermolecular C.C contacts of 3.083 (4) and 3.055 (4) A. Variable-temperature X-ray diffraction measurements performed between room temperature and 93 K showed a linear decrease of the lattice parameters, suggesting that there is no phase transition.

Journal Article↗

PubMed2003

(E,E,E)-1,6-Bis(2,4-dichlorophenyl)hexa-1,3,5-triene.

The title molecule, C(18)H(12)Cl(4), lies about an inversion centre and the hexatriene chain is planar. The torsion angle of the single bond between the planes of the chain and the benzene ring is -8.6 (3) degrees. The dihedral angle between the planes defined by the chains of adjacent molecules is 50.0 (2) degrees. The shortest intermolecular distance between the Cl atoms is 3.514 (1) A. The molecules are joined through pi-pi-stacking and strong attractive Cl.Cl interactions.

Journal Article↗

PubMed2002

Retention of configuration on the oxidative addition of P-H bond to platinum (0) complexes: the first straightforward synthesis of enantiomerically pure P-chiral alkenylphosphinates via palladium-catalyzed stereospecific hydrophosphinylation of alkynes.

The oxidative addition of pure (R(P))-menthyl phenylphosphinate 1 to a platinum (0) complex proceeds readily with retention of configuration at the chiral phosphorus center which was unambiguously confirmed by an X-ray analysis. In the presence of a catalytic amount of palladium, the hydrophosphinylation of a variety of alkynes with 1 also takes place stereospecifically, with retention of configuration, affording high yields of the corresponding vinylphosphinates bearing a single chirality at phosphorus.

Alkynes↗

PubMed2001

Rhodium-Catalyzed Hydrophosphorylation of Terminal Alkynes Leading to Highly Selective Formation of (E)-Alkenylphosphonates: Complete Reversal of Regioselectivity to the Palladium-Catalyzed Counterpart We are grateful to the Japan Science and Technology Corporation (JST) for financial support through the CREST (Core Research for Evolutional Science and Technology) program and for a postdoctoral fellowship to C.-Q.Z.

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Journal Article↗