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Masayuki Takeuchi

Publications and source records attributed to Masayuki Takeuchi.

34 records · Page 2Linked to original sources
PubMed2003

Facile deposition of [60]fullerene and carbon nanotubes on ITO electrode by electrochemical oxidative polymerization of ethylenedioxythiophene.

It was found that [60]fullerene encapsulated in p-sulfonatocalix[8]arene and single-walled carbon nanotubes (SWNTs) solubilized by sodium dodecylsulfate can be readily deposited on the ITO electrode by electrochemical oxidative polymerization of ethylenedioxythiophene (EDOT) without chemical modification of these carbon clusters. The driving force for the deposition is an electrostatic interaction between the anionic complexes and the cationic charges of poly(EDOT) formed in the oxidative polymerization process. The surface morphology was thoroughly characterized by scanning electron micrograph: the [60]fullerene/poly(EDOT) film is covered by nano-particles with 20-100 nm diameters whereas the SWNTs/poly(EDOT) film is covered by nanorods with several microm length and ca. 100 nm diameter. The results indicate that the anionic complexes act as nuclei for the polymer growth in the oxidation polymerization. Interestingly, when these modified ITO electrodes were photoirradiated, the appearance of a photocurrent wave was observed. The action spectra showed that the photoexcited energy of [60]fullerene or SWNTs is efficiently collected by the electroconductive poly(EDOT) film and transferred to the ITO electrode.

Journal Article↗
PubMed2003

Nano-rod structure of poly(ethylenedioxythiophene) and poly(pyrrole) as created by electrochemical polymerization using anionic porphyrin aggregates as template.

It was found that a one-dimensional rodlike structure of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) in water acts as a powerful template for electrochemical polymerization of ethylenedioxathiophene (EDOT) and pyrrole on an ITO electrode. Examination using CV and UV-vis spectroscopic examinations established that J-aggregated TPPS molecules are entrapped in the resultant poly(EDOT) and poly(pyrrole) films. SEM observation established that these monomers are electrochemically oxidized to grow up to a nanosized rodlike structure, reflecting the aggregation structure of TPPS. [structure: see text]

Journal Article↗
PubMed2003

Proton-sensitive fluorescent organogels.

A 1,10-phenanthroline-appended cholesterol-based gelator (1) and its nongelling reference compound (2) were synthesized. Among 19 solvents tested herein, gelator 1 could gelate 11 solvents including alcohols, dipolar aprotic solvents, organic acids and a base (triethylamine), indicating that 1 acts as a versatile gelator. The TEM observation gave a visual image showing that fibrillar aggregates are entangled in the three-dimensional network structure. In the fluorescence measurements, most gels afforded an emission maximum at 394 nm (purple emission), whereas only the acetic acid gel afforded an emission maximum at 522 nm (yellow emission). Thus, the influence of protonation of the 1,10-phenanthroline nitrogens (by trifluoroacetic acid) on the fluorescence properties in the gel phase was investigated in detail. The results have established that the fluorescence intensity of 1 x H+ becomes particularly strong in the gel phase, presumably because of the energy transfer from neutral 1* to protonated 1 x H+ and the restriction of the 1 x H+ molecular motion. The finding suggests the possibility that the gel system would be useful not only as a new proton-sensitive fluorescence system but also as a new medium for designing efficient energy transfer systems.

Journal Article↗
PubMed2003

Subcellular distributions of rat CaM kinase phosphatase N and other members of the CaM kinase regulatory system.

Ca2+/Calmodulin-dependent protein kinase (CaM kinase) regulatory system is composed of multifunctional CaM kinases such as CaM kinases IV and I, upstream CaM kinases such as CaM kinase kinases alpha and beta, which activate multifunctional CaM kinases, and CaM kinase phosphatases such as CaM kinase phosphatase and CaM kinase phosphatase N, which deactivate the activated multifunctional CaM kinases. To understand the combinations of CaM kinases I and IV, CaM kinase kinases alpha and beta, and CaM kinase phosphatases, the locations of the enzymes in the cell were examined by immunocytochemical studies of cultured cells. The results indicate that CaM kinase I, CaM kinase kinase beta, and CaM kinase phosphatase occur in the cytoplasm and that CaM kinase IV, CaM kinase kinase alpha (and CaM kinase kinase beta in some cell types and tissues), and CaM kinase phosphatase N occur inside the cellular nucleus, suggesting that there are at least two different sets of CaM kinase regulatory systems, one consisting of CaM kinase I, CaM kinase kinase beta, and CaM kinase phosphatase in the cytoplasm and the other consisting of CaM kinase IV, CaM kinase kinase alpha (and CaM kinase kinase beta in some cell types and tissues), and CaM kinase phosphatase N in the nucleus.

Amino Acid Sequence↗
PubMed2002

Allosteric Binding of an Ag+ Ion to Cerium(IV) Bis-porphyrinates Enhances the Rotational Activity of Porphyrin Ligands.

A series of cerium(IV) bis-porphyrinate double-deckers [Ce(bbpp)(2)] (BBPP=5,15-bis(4-butoxyphenyl)porphyrin dianion), [Ce(tmpp)(2)] (TMPP=5,10,15,20-tetrakis(4-methoxyphenyl)porphyrin dianion), [Ce(tfpp)(2)] (TFPP=5,10,15,20-tetrakis(4-fluorophenyl)porphyrin dianion), [Ce(tmcpp)(2)] (TMCPP=5,10,15,20-tetrakis(4-methoxycarbonylphenyl)porphyrin dianion), and [Ce(tmpp)(tmcpp)] was prepared. They bind three Ag(+) ions to their concave porphyrin pi subunits (pi-clefts) according to a positive homotropic allosteric mechanism with Hill coefficients (n(H)) of 1.7-2.7. The rotation rates of the porphyrin ligands in [Ce(bbpp)(2)] were evaluated to be 200 s(-1) at 20 degrees C (DeltaG$\rm{^{\ne }_{293}}$=14.1 kcal mol(-1)) and 220 s(-1) at -40 degrees C (DeltaG$\rm{^{\ne }_{233}}$=11.0 kcal mol(-1)) without and with Ag(+) ions, respectively. These results consistently support our unexpected finding that Ag(+) binding can accelerate rotation of the porphyrin ligand. On the basis of UV-visible, (1)H NMR, and resonance Raman spectral measurements, the rate enhancement of the rotational speed of the porphyrin ligands is attributed to conformational changes of the porphyrin in cerium(IV) bis-porphyrinate induced by binding of Ag(+) guest ions in the clefts. This novel concept of positive homotropic allosterism is applicable to the molecular design of various supramolecular and switch-functionalized systems.

Journal Article↗
PubMed2002

Allosteric binding of an Ag+ ion to cerium(IV) bis-porphyrinates enhances the rotational activity of porphyrin ligands.

A series of cerium(IV) bisporphyrinate double-deckers [Ce(bbpp)2] (BBPP = 5,15-bis(4-butoxyphenyl) porphyrin dianion), [Ce(tmpp)2] (TMPP = 5,10,15,20-tetrakis(4-methoxyphenyl)-porphyrin dianion), [Ce(tfpp)2] (TFPP = 5,10,15,20-tetrakis(4-fluorophenyl)porphyrin dianion), [Ce(tmcpp)2] (TMCPP = 5,10,15,20-tetrakis(4-methoxycarbonylphenyl)porphyrin dianion), and [Ce(tmpp)(tmcpp)] was prepared. They bind three Ag+ ions to their concave porphyrin pi subunits (pi-clefts) according to a positive homotropic allosteric mechanism with Hill coefficients (nH) of 1.7-2.7. The rotation rates of the porphyrin ligands in [Ce(bbpp)2] were evaluated to be 200 s-1 at 20 degrees C (delta G++293 = 14.1 kcal mol-1) and 220 s-1 at -40 degrees C (delta G++233 = 11.0 kcal mol-1) without and with Ag+ ions, respectively. These results consistently support our unexpected finding that Ag+ binding can accelerate rotation of the porphyrin ligand. On the basis of UV-visible, 1H NMR, and resonance Raman spectral measurements, the rate enhancement of the rotational speed of the porphyrin ligands is attributed to conformational changes of the porphyrin in cerium(IV) bis-porphyrinate induced by binding of Ag+ guest ions in the clefts. This novel concept of positive homotropic allosterism is applicable to the molecular design of various supramolecular and switch-functionalized systems.

Journal Article↗
PubMed2002

Stimulation of Ca(2+)/calmodulin-dependent protein kinase phosphatase by polycations.

Ca(2+)/calmodulin-dependent protein kinase phosphatase (CaMKPase) dephosphorylates and regulates multifunctional Ca(2+)/calmodulin-dependent protein kinases (CaMKs). One of the prominent features of CaMKPase is stimulation of phosphatase activity by polycations such as poly-L-lysine (poly(Lys)). Using various polycations, basicity and molecular weight of the polymer proved to be important for the stimulation. Surface plasmon resonance (SPR) analysis showed that CaMKIV(T196D), which mimics CaMKPase substrate, and CaMKPase could form tight complexes with poly(Lys). Pull-down binding experiments suggested that the formation of a tightly associated ternary complex consisting of CaMKPase, poly(Lys), and phosphorylated CaMKIV is essential for stimulation. Dilution experiments also supported this contention. Poly(Lys) failed to stimulate a CaMKPase mutant in which a Glu cluster corresponding to residues 101-109 in the N-terminal domain was deleted, and the mutant could not interact with poly(Lys) in the presence of Mn(2+). Thus, the Glu cluster appeared to be the binding site for polycations and to play a pivotal role in the polycation stimulation of CaMKPase activity.

Amino Acid Sequence↗
PubMed2002

Cooperative C(60) binding to a porphyrin tetramer arranged around a p-terphenyl axis in 1:2 host-guest stoichiometry.

[structure: see text] Porphyrin tetramer 1 was newly designed and synthesized to construct a novel cooperative [60]fullerene (C(60)) binding system. Compound 1 has a p-terphenyl axis, which is expected to act as a scaffold for a guest-binding information transducer. In toluene, 1 can bind 2 equiv of C(60) to produce a 1:2 1/C(60) complex with association constants of 5800 M(-1) (K(1)) and 2000 M(-1) (K(2)). These values are significantly greater than those for control porphyrin dimers such as 2 and 3.

Journal Article↗
PubMed2002

Selective phosphodiesterase type 4 inhibitors reduce the prolonged survival of eosinophils stimulated by granulocyte-macrophage colony-stimulating factor.

It is well known that bronchial asthma is defined as chronic eosinophilic inflammation of the respiratory tract and that as one of the various types of inflammatory cells, eosinophils induce the airway inflammation of chronic asthma. Granulocyte-macrophage colony-stimulating factor (GM-CSF) has been shown to play an important role in the prolongation of the survival of eosinophils. We investigated the inhibitory effect of the selective phosphodiesterase (PDE) 4 inhibitors, 3,4-dipropyl-4,5,7,8-tetrahydro-3H-imidazo[1,2-i]purin-5-one (XT-611) and rolipram, and the nonselective PDE inhibitor theophylline, against GM-CSF-induced prolongation of the survival of eosinophils isolated from patients with bronchial asthma. Eosinophils (10(6) cells/ml) were incubated in the presence of GM-CSF together with or without theophylline, rolipram or XT-611 at 37 degrees C, and the viable cells were assessed up to 4d using Trypan blue dye exclusion. The presence of theophylline (10(-4) M), rolipram (10(-4)-10(-5) M) or XT-611 (10(-4)-10(-5) M) significantly reduced the GM-CSF (10 pg/ml)-induced prolongation of viability of eosinophils. These findings suggest that selective PDE 4 inhibitors, including XT-611, may effectively reduce the activities of inflammatory cells in the airway of bronchial asthma patients.

3',5'-Cyclic-AMP Phosphodiesterases↗