Teruyuki Kodama

Cerium(IV)-oligoDNA hybrid as highly selective artificial nuclease

Abstract Cerium(IV) ion is attached to the 5′-end of a 19-mer DNA by use of iminodiacetate ligand. At pH 7.2 and 30 °C, the hybrid selectively cuts a 40-mer DNA, which has 19-mer sequence complementary with the DNA in the hybrid, at the target site (the 3′-side of the 19-mer portion of the substrate DNA). Cerium(IV) ion hydrolyzes thymidylyl(3′-5′)thymidine to thymidine without concurrent oxidative cleavage of the ribose, indicating that the selective scission by the hybrid proceeds via the hydrolysis of the phosphodiester linkage.

Preparation and properties of molybdenum and tungsten dinitrogen complexes: XXI. Trimethylsilylation of coordinated dinitrogen

Abstract The treatment of cis -[W(N 2 ) 2 (PMe 2 Ph) 3 with trimethylsilyl iodide in benzene gave two silylated compounds trans -[WI(NNSiMe 3 )(PMe 2 Ph) 4 ] and mer -[WI 2 (NNHSiMe 3 )(PMe 2 Ph) 3 ], X-ray analyses of which disclosed the trimethylsilyldiazenido and trimethylsilylhydrazido(2−) structures, respectively. Analogous products were also prepared from the reactions of trans -[W(N 2 ) 2 (dpe) 2 ], trans -[W(N 2 ) 2 (dpe)(PPh 2 Me) 2 ] and trans -[W( n PrCN)(N 2 )(dpe) 2 ] (dpe = Ph 2 PCH 2 CH 2 PPh 2 ) with trimethylsilyl iodide.

Preparation and properties of molybdenum- and tungsten-dinitrogen complexes 7 [1]. The molecular structure of MoCl(N2COPh) (Ph2PCH2CH2PPh2)2.

Abstract The structure of the complex MoCl(N2COPh)(Ph2PCH2CH2PPh2)2 has been determined from three-dimensional X-ray counter data collected on a single crystal. The material crystallizes in space group P21/n of the monoclinic system with four formula units of the complex in a cell of dimensions a = 21.17(1) A, b = 19.97(1) A, c = 12.56(2) A, β = 100.57(3)°, V = 5220.6(52) A3. The structure has been refined by blockdiagonal least-squares techniques to a final R index 0.0715 based on 7386 reflections above background. The complex has, an octahedral geometry with benzoyldiazenido and chloride ligands in a trans position and the benzoyldiazenido ligand is not chelating through the carbonyl oxygen. The bond orders of NN, NC, and CO are estimated to be 1.85, 1.3, and 1.85, respectively, which indicate the mesomeric spread of a high electron density from the metal to the benzoyldiazenido ligand. However, this spread does not extend so far to the phenyl group.

Efficient and oxygen-independent hydrolysis of single-stranded DNA by cerium(IV) ion

Cerium(IV) ion efficiently hydrolyses the phosphodiester linkages in DNAs, even in the absence of molecular oxygen. The pseudo first-order rate constant for the hydrolysis of thymidylyl(3′,5′)thymidine (TpT) by Ce(NH4)2(NO3)6(0.01 mol dm–3) at pH 7 and 50 °C is 1.9 × 10–1 h–1(the half-life is 3.6 h), either with or without molecular oxygen. DNA hydrolysis by CeCl3 requires molecular oxygen to convert the CeIII ion to CeIV. Addition of hydrogen peroxide causes various side-reactions rather than accelerating the hydrolysis. The hydrolysis by CeIV proceeds via P–O scission, as confirmed by the absence of 18O incorporation into thymidine (T) during the reaction in an H218O–H216O mixture. There exists no specific base-preference in the scission, and concurrent oxidative cleavage of the deoxyribose is nil. The activity of CeIV is more than 200 fold greater than those of trivalent lanthanide ions and of other tetravalent ions. A significant D2O solvent isotope effect and the pH independence of the hydrolysis rate indicate that the hydrolysis proceeds via an intramolecular attack by the CeIV-bound hydroxide ion and that the reaction is further assisted by the general acid catalysis of another water bound to the CeIV ion.

Aluminum coating on carbon materials by thermal decomposition of organoaluminum compounds in liquid phase.

炭素材料は表面を酸化し, SnCl2 で感受性化, PdCl2 で活性化処理を行ない, 15% トリイソブチルアルミニウムのジフェニルメタン溶液とともに約 220℃ に加熱すると,炭素材料表面をアルミニウム金属でコーティングすることができた。コーティングしたカーボンブラックを 70 気圧, 600℃,真空下で10 分間ホットプレスし,アルミニウム-炭素複合材料を製作した。これはコーティングしないカーボ ンブラックとアルミニウム粉末との複合材料にくらべて,圧縮強度が増大した。この複合材料にはアルミニウムカーバイドはほとんど生成していなかった。有機溶媒中,有機アルミニウム化合物を用いて,アルミニウムをコーティングする方法は炭素とアルミニウムのぬれを改善し,均噌にコーティングでき,しかもアルミニウムカーバイドの生成を搾劇することができる点において有利であることがわかった。