Spectroscopic investigation of cyclodextrin monomers,derivatives, polymers and azo dyes (1)

Circular dichroism (CD) and visible spectra of inclusion compounds between Methyl Orange (MO) analogues and -, -, -cyclodextrin (cdx), 2,6-dimethyl-and 2,3,6-trimethyl--cdx, water soluble -, -, -cdx polymer products were investigated. In the CD-spectroscopic investigation, the complex with -cdx epichlorohydrin condensate showed a large amplitude and splitting of the induced ^* band. Fractions of glyceryl ether of less than 2000 and polymer of more than 10000 dalton molecular mass were separated. Complexes of above two fractions and MO showed the same splitting spectral pattern. Job's plots from visible spectra showed the formation of the 11 complex and CD-data suggested the co-existence of the 21 MO-cdx complex. This splitting pattern showed the reversal of the signs when -cdx-ethyleneglycol-bis(epoxypropyl) ether was used and disappeared when larger host molecules and azo dyes were used. The splitting was explained by exciton interaction.     

Direct UHV-TEM observation of palladium clusters on a silicon surface.

About 1 monolayer of palladium was deposited onto a silicon (111) 7 x 7 surface at a temperature of about 550 K inside an ultrahigh vacuum transmission electron microscope, resulting in formation of Pd2Si nanoislands and a 1 x 1 surface layer. Pd clusters created from an excess of Pd atoms on the 1 x 1 surface layer were directly observed by in situ plan view high-resolution transmission electron microscopy. When an objective aperture was introduced so that electron diffractions less than 0.20 nm were filtered out, the lattice structure of the 1 x 1 surface with 0.33 nm spacing and the Pd clusters with a trimer shape were visualized. It was found that image contrast of the 1 x 1 lattice on the specific height terraces disappeared, and thereby an atomic structure of the Pd clusters was clearly observed. The appearance and disappearance of the 1 x 1 lattice was explained by the effect of the kinematical diffraction. It was identified that a Pd cluster was composed of three Pd atoms without a centered Si atom, which is consistent with the model proposed previously. The feature of the Pd clusters stuck at the surface step was also described.     

Hydrosilylation of α,β-unsaturated nitriles and esters catalyzed by tris (triphenylphosphine)chlororhodium

The hydrosilylation of α,β-unsaturated nitriles and esters such as acrylonitrile, crotononitrile, cinnamonitrile, ethyl and methyl acrylate, ethyl and methyl crotonate and ethyl and methyl methacrylate using tris(triphenylphosphine)chlororhodium as a catalyst is described. The hydrosilylation of α,β-unsaturated nitriles provided α-adduct exclusively in high yield except in the case of trichlorosilane which afforded β-adduct with acrylonitrile. On the other hand, the hydrosilylation of α,β-unsaturated esters gave rather complex results. The selectivity of the reactions was dramatically affected by the substituent of the ester group and that on the β-carbon. Thus, the hydrosilylation of ethyl acrylate with triethylsilane afforded a β-adduct, but, that of ethyl crotonate using the same hydrosilane gave a 1,4-adduct exclusively. Possible mechanisms for these reactions are discussed.     

Enhanced optical sensing of anions with amide-functionalized gold nanoparticles

A gold nanoparticle surface-modified with amide ligands shows enhanced optical sensing of anions: the detection limit is increased by about three orders of magnitude higher than that originally expected from the anion binding ability of neutral amide ligands.     

Developmental changes of poly(ADP-ribose) polymerase expression in Sarcophaga peregrina

To elucidate the physiological role of poly(ADP-ribose) polymerase (PARP), we studied the levels of PARP mRNA and protein during the developmental stages of Sarcophaga peregrina. PARP mRNA expression changed remarkably throughout the developmental stages. The level of PARP mRNA (the molecular ratio of PARP mRNA to the total RNA) was highest in unfertilized eggs and that of PARP protein (the molecular ratio of PARP protein to the total protein of the crude extract) was high in unfertilized and fertilized eggs and in 1st instar larvae. During the embryogenesis period, the levels of PARP mRNA and protein gradually decreased. The levels of PARP mRNA during larval and pupal periods became less than about 5% of that in unfertilized eggs. After the emergence of adult flies, the levels of PARP mRNA and protein increased both in female and male flies. PARP activity normalized with the total amount of protein in the crude extract changed in parallel to the level of PARP protein throughout the developmental stages. The biological significance of the drastic change of mRNA and protein levels of PARP still remains to be clarified.     

Synthetic studies of carzinophilin. Part 1: Synthesis of 2-methylidene-1-azabicyclo[3.1.0]hexane systems related to carzinophilin

Synthesis of the model compounds of carzinophilin carrying 2-methylidene-1-aza-bicyclo[3.1.0]hexane systems was achieved. Formation of malonylidenes or N-acyl-glycinylidenepyrrolidines was carried out by utilizing Eschenmoser's sulfide contraction or Herdeis's condensation between the 2-methylthio-Δ¹-pyrrolone derivatives and ethyl nitroacetate, respectively. The 1-azabicyclo-[3.1.0]hexane systems were constructed by base-promoted aziridine formation.     

13C Nuclear magnetic resonance spectra of cyclodextrin monomers,derivatives and their complexes with methyl orange

Low molecular mass fractions of water soluble -, -, and -cyclodextrin epichlorohydrin polymer products (cdx-Ep) were characterized by¹³C nuclear magnetic resonance. The derivatives proved not to be polymers, but substituted cdx having one or two glyceryl groups per one glucose at the C-2, C-3 and C-6 positions. Spectra of analogous hydroxy-propyl -cdx indicate that the degree of substitution is rather higher at the C-6 position. Methyl orange (MO) was included into nine kinds of cdx having different inner diameters and hydrophobic torus heights; -, -, and -cdx monomers, 2, 6-dimethyl and 2, 3, 6-trimethyl -cdx, water soluble -, -, and -cdx-Ep and ethyleneglycol-bis(epoxy-propyl) ether products. The inclusion shifts were compared with each other and with the dioxane-induced solvent shift of MO. TheN, N-dimethyl-aniline side of MO shifted to a higher field site with the increase of the inner diameter in cdx. By substituting cdx with ether groups of different length, the mechanism of inclusion formation remains substantially the same, but by lengthening the hydrophobic cavity, the hydrophobic interaction becomes stronger, as a better resemblance of inclusion shifts and solvent shifts can be observed.Presented at the Fourth International Symposium on Inclusion Phenomena and the Third International Symposium on Cyclodextrins, Lancaster, U.K., 20–25 July 1986.     

Regio-specific behaviour in electrochemical two-electron reduction of NAd+ analogs

Conflicting pecificities were observed in electro-chemical 2e-reductions of NAD⁺ analogs: 1-phenyl-3-aminocarbonylpyridiniums gave quantitatively 1,4-dihydronicotinamides whereas 1-benzyl and 1-methyl derivatiives gave 1,6-isomers.     

Determination of selenium in sediment by isotope-dilution inductively coupled plasma mass spectrometry with an octapole reaction cell

A method is described for determination of selenium in sediment by isotope-dilution inductively coupled plasma mass spectrometry with an octapole reaction cell (ID–ICP–ORCMS). Sediment samples were digested with HNO₃, HClO₄, and HF, and the digestion included an elaborate evaporation process to remove bromine from the digested solution. Simple strong cation-exchange disk filtration was used to remove rare earth elements (REE) from the digested solution, because REE²⁺ seriously interfere with Se isotopes (i.e. ¹⁵⁶Gd²⁺ with ⁷⁸Se⁺, ¹⁶⁰Gd²⁺ with ⁸⁰Se⁺). Addition of acetic acid to the filtrate was examined to improve the sensitivity of ICP–ORCMS measurement of Se⁺ by means of a carbon-enhancement effect. The interfering for selenium isotopes were almost eliminated by use of H₂ as reaction gas. Interference from BrH⁺ formed in the reaction cell was negligible because the Br was removed in the evaporation process. Approximately 99.5% of REE were removed by cation-exchange disk filtration yet more than 99% of Se remained in the filtrate solution. The intensity for Se⁺ was enhanced approximately fourfold by addition of 5% (v/v) of acetic acid whereas that for was barely enhanced. Measured ⁸⁰Se/⁷⁸Se ratios in unspiked digested solutions of the sample were in good agreement with that for an Se standard solution. The analytical results for Se in the certified reference materials MESS-3 and PACS-1 were in good agreement with their certified values, with small uncertainties.      

γ‐Cyclodextrin as Inhibitor of the Precipitation Reaction between Berberine and Glycyrrhizin in Decoctions of Natural Medicines: Interaction Studies of Cyclodextrins with Glycyrrhizin and Glycyrrhetic Acid by 1H‐NMR Spectroscopy and Molecular‐Dynamics Calculation

To prevent the precipitation reaction between glycyrrhizin ( 1 ) and berberine ( 3 ) in the decoctions of Glycyrrhiza/Coptis rhizome or Glycyrrhiza/Phellodendron bark, the presence of cyclodextrin (CD) in the mixture was proven to be effective. The preventing effect decreased in the order γ‐CD>β‐CD, and no effect was observed for α‐CD. On the other hand, the extraction degree of 1 from the natural medicine Glycyrrhia was considerably increased in the presence of γ‐CD, γ‐CD being much more effective than α‐ or β‐CD. Thus, the blocking effect of CD on the precipitate formation between 1 and 3 is suggested to be primarily dependent on the stability of the inclusion complex of the CD with 1 . To establish the structure of such a preferred inclusion complex, the interactions of 1 with β‐ and γ‐CDs were investigated by ¹H‐NMR spectroscopy and molecular‐dynamics (MD) calculations. The ¹H‐NMR measurements showed that the increase in solubility of 1 in H₂O is dependent on the degree of its inclusion into the CD, which depends on the molecular size of the CD. The MD calculations suggested that the H‐bond interactions are sufficiently strong to form a stable [ 1 /γ‐CD] complex, in which the lipophilic rings C, D, and E of 1 are fully inserted into the molecular cavity of γ‐CD, thus forming a kind of structure covered by a hydrophilic molecular capsule, while such an interaction mode is impossible for α‐ or β‐CD.