Shunro Yamaguchi

Affinity binding phenomena of DNA onto apatite crystals

The effect of DNA on the crystal growth of hydroxyapatite (HAp) and its morphology was examined. X-ray diffraction patterns of DNA-containing apatites showed typical apatitic features. However, crystal growth was greatly inhibited in the presence of DNA during synthesis; particularly, the crystallinity in the a-axis direction decreased dramatically at low concentrations of DNA. The a- and c-axis dimensions of each precipitate were almost the same, which implies that DNA molecules affect only the crystal surface. CHN analysis clearly showed the presence of these elements, which increased with an increase in DNA concentration in the solution. Scanning electron micrographs of the precipitates formed in the presence of DNA showed typical needle-like crystals, with a decreased crystal size, especially width. Infrared absorption spectroscopy of the DNA-containing apatites showed that the 1630-1700 cm(-1) absorption band due to C=C and C=N stretching increased with an increase in DNA concentration during precipitation. The ESCA spectrum of HAp(DNA 1.0) shows N 1s and C 1s peaks that are absent and weak, respectively in HAp. 31P NMR spectroscopy revealed a weak peak at the base of the 31P peak from the PO4(3-) ions in the HAp crystals. This weak 31P peak had a small positive shift from the position found in native DNA which may be due to the phosphate backbone of adsorbed DNA. The apparent solubility of the HAps increased with an increase in DNA concentration. These results suggest that there is an affinity binding between apatite crystal and DNA molecules.

Structural study of phosphate groups in layered metal phosphates byhigh-resolution solid-state31P NMR spectroscopy

In studies of a series of crystals of layered metal phosphate compounds by magic angle spinning (MAS) NMR spectroscopy, it has been found that there is a distinct correlation between the 31 P isotropic chemical shift value and the type of phosphate group. The isotropic 31 P chemical shifts of (H 2 PO 4 ) - , (HPO 4 ) 2- and (PO 4 ) 3- groups appear around δ -10, -20 and -30, respectively. These assignments were made unambiguously by measuring the 31 P MAS NMR spectra with and without 1 H high-power decoupling together with the cross-polarization transfer technique between 1 H and 31 P nuclei (CP MAS spectra).

Synthesis and evaluation of various layered octacalcium phosphates by wet-chemical processing

Octacalcium phosphate was synthesized by hydrolysis of α-tricalcium phosphate through a wet-chemical processing. Using the same wet-chemical processing in presence of various succinate ions, the preparation of some complexed octacalcium phosphates was attempted. The products were examined by X-ray diffraction method. These complexed octacalcium phosphates intercalated with succinic acid, L-asparatic acid, and methyl succinic acid showed an expanded basal spacing in the octacalcium phosphate unit cell dimensions. The microstructure was observed by scanning and transmission electron microscopy.

Keggin-type polyacid clusters on apatite: characteristic catalytic activities in solvent-free oxidation

We found that Keggin-type phosphometalates are effective catalysts for solvent-free oxidation with urea–H2O2 by dispersing on fluorapatite solid phase. In the solid phase system the phosphomolybdate (NH4)3PMo12O40 was more effective than the phosphotungstate (NH4)3PW12O40, whereas the latter was much superior to the former in the liquid-phase reaction with aqueous H2O2. In situ formation of novel peroxo-type species from (NH4)3PMo12O40/FAp and urea–H2O2, which may lead to the high catalytic activity in the solid phase system, was observed by 31P solid-state NMR.

Synthesis of 29,29,30,30-tetracyanobianthraquinodimethane

29,29,30,30-Tetracyanobianthraquinodimethane (TBAQ) was prepared by the reaction of bianthrone with malononitrile in pyridine and its structure and properties were described.

Catalytic properties of holmiumdecatungstate modified with cetylpyridinium cation [{C5H5N(CH2)15CH3}7H2Ho(III)W10O36; Cetyl-HoW10] for H2O2-oxidation of alcohols and olefins and its working states under an organic-solvent-free condition

Catalytic properties of holmiumdecatungstate modified with cetylpyridinium cations [Cetyl-Ho(III)W10] for H2O2-oxidations of alcohols and olefins were investigated under various organic solvents-aqueous H2O2 biphasic conditions. Generally, secondary alcohols and benzyl alcohols and internal olefins such as cyclooctene were efficiently catalyzed by Cetyl-Ho(III)W10, while primary alcohols and terminal olefins were almost not. The activity for 2-octanol grew much by using a smaller amount of nonpoler solvents such as CHCl3. Especially, in an organic-solvent-free condition as a limited case, Cetyl-Ho(III)W10 was elucidated to be workable as a highly active but quite mild catalyst in comparison with the other heteropolyoxometalates well known. A schematical model on the working states was successfully presented. The present H2O2-Cetyl-Ho(III)W10 catalyst system will be insisted, finally, to be responsible for industrial oxidation processes such as being performed in a non-organic solvent system as environmental concerns.

Catalytic behavior of a series of lanthanide decatungstates [Ln(III)W10O369−; Ln: LaYb] for H2O2-oxidations of alcohols and olefins. Some chemical effects of the 4fn-electron in the lanthanide(III) ion on the catalyses

Abstract The catalytic activities of a series of lanthanide decatungstates [Ln(III)W 10 O 36 9 ; Ln(III)W10, Ln: LaYb] modified with cetyl-pyridinium cations for H 2 O 2 -oxidation of both cyclooctene to epoxycyclooctane and benzyl alcohol to benzaldehyde were investigated in a CHCl 3 -aqueous H 2 O 2 biphasic system. The activity for the former reaction decreased almost linearly along with the contraction of the Ln(III) ion in Ln(III)W10, and on the contrary, that for the latter tended to increase. The activity for the alcohol correlated, additionally, with the physicochemical parameters of LN(III)W10. A chemical effect of the 4f n -electrons in the lanthanide(III) ion on such catalytic behavior will be discussed from a mechanistic viewpoint.

Shape-controlled synthesis of hydroxyapatite from α-tricalcium bis(orthophosphate) in organic-aqueous binary systems

Hydrolyses of α-tricalcium bis(orthophosphate) Ca3(PO4)2 (α-TCP) were carried out in a heterogeneous solvent system (hydrophobic organic solvent-water). The hydroxyapatites (HAp) formed were deficient in calcium (Ca/P = 1.56–1.61, a-axis = 0.9440 nm, c-axis = 0.6880 nm) and contained acid phosphate (and sometimes carbonate depending on the organic solvent used). The HAp was in the form of needles with a length (1–4 μm) that depended on the polarity of the hydrophobic organic solvent. The aspect ratio was highest in 1-octanol with a polarity of ET = 48.3. On the other hand, in a hydrophobic organic solvent system without OH groups such as n-octane (ET = 31.1), HAp formed fine particles that are similar to HAp prepared in a system without an organic solvent. Thus, hydrophobicity and OH groups of organic solvents affect the crystal growth of HAp.

A new approach to an artificial joint based on bio-cartilage/porous β-tricalcium phosphate system

Abstract A new artificial joint model based on the system of bio-cartilage and porous β-tricalcium phosphate (TCP) was fabricated. The porous β-TCP with 100 μm or so of average pore diameter was prepared by hydrothermal treatment and successive ceramic foaming method. The bio-cartilage part consisted of 0.15% collagen gel with chondrogenic ATDC5 cells. ATDC5 cells in the bio-cartilage/porous β-TCP system were cultured to give an artificial joint model. In the artificial joint model, metachromasia was observed with toluidine blue staining. From the FT-IR spectra of the bio-cartilage, formation of proteoglycans was suggested. In addition, alkaline phosphatase activity increased dramatically. ATDC5 cells grew to produce cartilage matrices in this system.

A novel acid-catalyzed transformation of octadienynedial derivatives to cyclopenta[b]-thiapyrans and cyclopenta[b]pyran.

Abstract Substituted 2,6-octadien-4-ynedial derivatives were synthesized, which give cyclopenta[b]thiapyran or cyclopenta[b]pyran derivatives by intramolecular cyclization.