Density functional calculations of dangling bonds for CN and SiN films

Hyperfine interaction constants (HFICs) of dangling bonds for CN and SiN films were calculated by density-functional theory. The averaged ¹⁴N isotropic HFICs for C dangling bonds are almost equal to those for Si dangling bonds. The anisotropic ¹⁴N HFICs calculated for C dangling bonds are larger than those for Si dangling bonds by a factor 2. The calculated results were compared with experimental results obtained by electron spin resonance and electron nuclear double resonance. It was indicated that the carbon dangling bonds are located such that they avoid N atoms in CN films.     

Inclusion behavior of thiacalix[4]arenetetrasulfonate toward water-miscible organic molecules studied by salting-out and X-ray crystallography

[reaction: see text] Inclusion ability of thiacalix[4]arenetetrasulfonate (TCAS) toward water-miscible organic molecules such as alcohols, ketones, cyclic ethers, and so on was studied by salting-out of the inclusion complex. NMR spectra of the recovered precipitates showed size selectivity to include the guest molecules. X-ray crystallographic analyses of TCAS salts including acetone and 1,4-dioxane suggested that guests are retained with the aid of cation coordination and H-bonding.     

CHANGES IN THE PATTERNS OF BIOSYNTHESIS and COMPOSITION OF AMINO ACIDS IN A MARINE PHYTOPLANKTER EXPOSED TO ULTRAVIOLET-B RADIATION: NITROGEN LIMITATION IMPLICATED

Abstract— The impact of ultraviolet-B radiation (UVBR) on the biosynthesis and the composition of intracellular dissolved free and combined amino acids was examined in nitrate-replete and nitrate-deficient cultures of Tetraselmis sp. Several similarities were observed in the response of Tetraselmis sp. to nitrogen deficiency and exposure to UVBR, in support of a view that UVBR affects amino acid synthesis in phytoplankton via its inhibitory effects on nitrogen assimilation into the cells. At levels that still permitted the uptake of carbon into the cells, both nitrogen deficiency and UVBR exposure resulted in a reduction in the overall rates of carbon incorporated into amino acids, an increase in the absolute concentrations of amino acids within the intracellular dissolved free amino acid (INDFAA) pool and a decrease in the total cellular amino acid (TCAA) pool. An examination of the patterns of carbon assimilation into individual amino acids in cells exposed to UVBR revealed similarities with the patterns in cells subject to nitrogen deficiency. The most conspicuous changes from the controls included an increased incorporation of ¹³C into glutamic' acid (glutamic acid + glutamine) and aspartic acid and a marked reduction into alanine and valine. Changes in the concentrations of amino acids within the INDFAA and TCAA pools were also similar in nitrate-deficient and UVBR-exposed cells and resembled the carbon assimilation patterns. These results strongly suggest that UVBR-induced changes in the biosynthesis and composition of amino acids are probably via its suppression of nitrogen assimilation into the cells.     

Novel acyl alpha-pyronoids, dictyopyrone A, B, and C, from Dictyostelium cellular slime molds

For the elucidation of the diversity of secondary metabolites of Dictyostelium cellular slime molds, we investigate the constituent of three species of slime molds. From the methanol extract of their fruit bodies, we obtained three novel compounds, dictyopyrone A (1) and B (2) from D. discoideum and D. rhizoposium and dictyopyrone C (3) from D. longosporum. They possess a unique alpha-pyrone moiety with a side chain at the C-3 position. Their relative structures were elucidated by spectral means, and the absolute configuration was confirmed by asymmetric synthesis of 1. Since these compounds were obtained from different species of Dictyostelium slime molds, they may be a type of compound common to this genus.     

Binding of metal ions by polyethylenimine and its derivatives

Measurements have been made of the binding of divalent metal ions, Cu²⁺, Ni²⁺, Co²⁺, and Zn²⁺ ions, by polyethylenimine (PEI) and its acetyl or alkyl derivatives by the equilibriumdialysis technique. These metal ions, in particular the Cu²⁺ ion, exhibited tremendously remarkable binding affinity toward PEI. The extent of complexation of the polymer with the metal ions was decreased markedly by acetylation or alkylation of the polymer. PEI with no primary amine showed an appreciable decrease in its affinity for the metal ion. These results indicate the participation of the primary amine of the polymer in the formation of the complex. A cooperative binding isotherm was observed in PEI–metal ion complex formation, suggesting swelling or conformational change of the polymer induced by this coordination process. Binding of the Cu²⁺ ion by PEI was found to be essentially independent of temperature over the range 5–35°C.     

Studies on the syntheses of heteroeyelie compounds. Part DVII. A synthesis of (±)-N-norgalanthamine

(±)-N-Norgalanthamine (la) and (±)-N-norlycoramine (Ib) was synthesized through the phenolie oxidation of N-(4-hydroxyphenethyl)-2-bromo-5-hydroxy-4-methoxybenzamide (lIb).     

Studies on the syntheses of heterocyclic compounds. Part CCCXXX Synthesis of a homocularine type compound

An intramolecular Ullmann reaction of bromophenethylisoquinoline (X) was investigated in order to obtain the homocularine type compound (V), which could be one of the potential alkaloids belonging to 1-phenethylisoquinoline series. Methylation of the phenolic 8-hydroxyisoquinoline (XVIII), one of the position isomers which was separated by silica gel chromatography from a mixture of 6-hydroxy- (XVII) and 8-hydroxyisoquinoline (XVIII) prepared as usual, gave the starting material (X), which was cyclized by the Ullmann reaction in the presence of cupric oxide. The structure of our objective homocularine (V) was assigned from spectral data.     

A Dodecalanthanide Wheel Supported by p‐tert‐Butylsulfonylcalix[4]arene

A dodecaholmium wheel of [Ho₁₂(L)₆(mal)₄(AcO)₄(H₂O)₁₄] ( 1 ; mal=malonate) was synthesized by using p‐tert‐butylsulfonylcalix[4]arene (H₄L) as a cluster‐forming ligand. The wheel consists of three fragments of mononuclear A^3? ([Ho(L)(mal)(H₂O)]^3?), trinuclear B^3? ([Ho(H₂O)₂(mal)(Ho(L)(AcO))₂]^3?), and C³⁺ ([Ho(H₂O)₂]³⁺), and an alternate arrangement of these fragments (A^3?? C³⁺? B^3?? C³⁺? A^3?? C³⁺? B^3?? C³⁺? ) results in a wheel structure. The longest and shortest diameters of the core were estimated to be 17.7562(16) and 13.6810(13) Å, respectively, and the saddle‐shaped molecule possesses a pocketlike cavity inside.     

Highly diastereoselective chemoenzymatic synthesis of (2′R)- and (2′S)-2′-deoxy[2′-H]guanosines

In an effort to develop an efficient synthetic method of highly diastereoselective (2′R)- and (2′S)-2′-deoxy[2′-²H]guanosines, chemoenzymatic conversion was investigated. The synthesis of (2′R > 98% de)-2′-deoxy[2′-²H]guanosine was achieved by biological transdeoxyribosylation using (2′R > 98% de)-2′-deoxy[2′-²H]uridine, 2,6-diaminopurine, and Enterobacter aerogenes AJ-11125, followed by treatment with adenosine deaminase. (2′S > 98% de)-2′-Deoxy[2′-²H]guanosine was synthesized from (2′S > 98% de)-2′-deoxy[2′-²H]uridine and 2,6-diaminopurine using thymidine phosphorylase and purine nucleoside phosphorylase instead of E. aerogenes AJ-11125.