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71.
Characterization of microbial poly (ε-l-lysine) by FT-IR, Raman and solid state C NMR spectroscopies
The molecular structure and conformation of microbial poly(ε-l-lysine) (M-ε-PL) produced by a variant of Streptomyces albulus were studied by means of FT-IR, FT-Raman and solid-state 13C NMR spectroscopies. Vibrational results indicate that M-ε-PL assumes a β-sheet conformation in the solid state. Solid state 13C NMR spectra of the crystalline and the amorphous components were observed separately and the degree of crystallinity was estimated to be 63%. A plausible conformation model was proposed. 相似文献
72.
Hiroaki Tada Tetsuji Ishida Ayako Takao Seishiro Ito Sudip Mukhopadhyay Tomoki Akita Koji Tanaka Hisayoshi Kobayashi 《Chemphyschem》2005,6(8):1537-1543
TiO2 particles loaded with silver nanoparticles with a mean diameter of 1.5 nm exhibit a high photocatalytic activity (84 % conversion after 1 h irradiation) for the reduction of nitrobenzene to aniline with 100 % selectivity in the presence of CH3OH (concentration=100 mM). High-resolution transmission electron microscopic studies of Pt-photodeposited Ag/TiO2 demonstrate that the Ag nanoparticles act as reduction sites in the photocatalytic reaction. Both spectroscopic measurements and density functional theory (DFT) calculations reveal that nitrobenzene is selectively adsorbed onto the Ag surfaces of Ag/TiO2 via partial electron transfer from Ag to nitrobenzene, whereas the interaction between aniline and Ag/TiO2 is weak. The kinetic analysis indicates that the recombination between the electrons flowing into the Ag nanoparticle and the holes left in the TiO2 valence band is significantly suppressed, particularly in the presence of CH3OH. The high activity and selectivity in the present Ag/TiO2-photocatalyzed reduction are rationalized in terms of the charge separation efficiency, the selective adsorption of the reactants on the catalyst surfaces, and the restriction of the product readsorption. 相似文献
73.
Hiroyuki Yamamoto Ayako Nishida Tomoyuki Takimoto Akira Nagai 《Journal of polymer science. Part A, Polymer chemistry》1990,28(1):67-74
Poly(L -ornithine) having azo aromatic side chain was synthesized by the water-soluble carbodiimide procedure. The photochemical properties of the azo polypeptide poly[Nδ-p-(phenylazo)benzoyl-L -ornithine] (PPABLO) was investigated by absorption and circular dichroism spectroscopy in hexafluoro-2-propanol (HFIP). The photochromism of the dichroic bands in the visible and ultraviolet wavelength regions was found to be reversible as a function of irradiation time at different wavelengths due to the photostationary state (about 70% trans)–cis photoisomerization of the azo aromatic moieties. The reversible photoinduced solubility change was also studied. On irradiation PPABLO is soluble under ultraviolet light (cis) and precipitate under visible light (70% trans) in HFIP–water. A discussion was presented that includes results on azo aromatic poly(L -lysine). 相似文献
74.
Tonegawa H Kuboe Y Amaike M Nishida A Ohkawa K Yamamoto H 《Macromolecular bioscience》2004,4(5):503-511
Poly(L-lysine)s having an Nepsilon-substituted tetrapeptide, Lys-Gly-Tyr-Gly, were synthesized by the coupling of the protected tetrapeptide active ester, Boc-Lys(Z)-Gly-Tyr(Bzl)-Gly (4-hydroxyphenyl)dimethylsulfonium methylsulfate and Nepsilon-group of the poly(L-lysine) side chain. The Nepsilon-substituted tetrapeptide functions as the substrate of tyrosinase and is responsible for the enzyme-mediated interpolymer cross-linking. The degree of Nepsilon-substitution (DS) was mostly controlled by changing the stoichiometry between the Nepsilon-amino groups of the parent poly(L-lysine) and the protected tetrapeptide active ester. Two kinds of samples having DS values of 8.6 and 18 mol-% were prepared. The resulting cationic Nepsilon-(Lys-Gly-Tyr-Gly)-poly(L-lysine) (abbreviated as PLL(GYGK)) was spun into hybrid fibers with the anionic polysaccharide gellan via a polyionic complexation reaction at the interface between aqueous solutions of the two polymers. The mechanical strengths of the PLL(GYGK)-gellan hybrid fibers were superior to those of the original poly(L-lysine)-gellan fibers. The mechanical strength of the hybrid fibers further increased upon the tyrosinase-mediated cross-linking reaction of the PLL(GYGK). This result indicates that the covalent cross-bridge formation between the Nepsilon-substituted peptides significantly contributed to reinforcement of the hybrid fibers. The present study affords a new methodology for reinforcement inspired by a biological process. 相似文献
75.
A new triterpenoid along with four known compounds were isolated from the leaves of Lagerstronemia speciosa (L.) PERS. (Lythraceae). On the basis of chemical and spectroscopic evidence, the new compound was established as 3beta,23-dihydroxy-1-oxo-olean-12-en-28-oic acid. 相似文献
76.
A fast method to obtain a quantitative structure-retention relationship is required in chromatography for the rapid optimization of chromatographic separation conditions. Chromatographic data of acidic drugs are analyzed by a computational chemical method to simulate chromatographic simulation. The direct interaction between a model phase and a drug is calculated as an energy value using the molecular mechanics calculation of CAChe. Computational chemistry using a model adsorbent is a new method for quantitative analysis of retention in reversed-phase liquid chromatography. The correlation coefficient is 0.878 (n = 19) between the retention factors of acidic drugs and interaction energy values of the final structure (DeltaFS) between an acidic drug and model pentyl-bonded phase. 相似文献
77.
Isao Kitagawa Hirotaka Shibuya Hiromichi Fujioka Yoshio Yamamoto Akiharu Kajiwara Kunihiro Kitamura Ayako Miyao Toshio Hakoshima Ken-ichi Tomita 《Tetrahedron letters》1980,21(20):1963-1966
Acid treatment of (IR, 3S,1′S)-1-(1′,2′-Epoxyethyl)-1,2,2-trimethyl-3-acetoxymethyl-cyclopentane ) has been shown to yield three products (, , ), among which and are 1-oxa-bicyclo[3.3.0]octane derivatives formed successive methyl migrations followed by an oxorane ring closure. 相似文献
78.
Issei Kasahara Masami Kanai Masako Taniguchi Ayako Kakeba Noriko Hata Shigeru Taguchi Katsumi Goto 《Analytica chimica acta》1989
The singly charged complex anion bis[2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulphopropylamino)phenolato]cobaltate(III) is intensely purple-violet and is stable over the pH range 1–13. Its absorption spectrum remains the same over this pH range. At pH2, it forms extractable ion pairs with long-chain quaternary ammonium ions and protonated alkylamines. Only the quaternary ammonium ions are extracted into chloroform at pH 11, hence separate extractions allow both types to be determined. The absorbance of the organic phase is measured at 594 nm. The apparent molar absorptivity is 7.0 × 104 l mol?1 cm?1. Calibration graphs for zephiramine, benzethonium and hexadecylpyridinium ions are linear over the range 0.1–2 × 10?6 M. The only interference found was from anionic surfactants. The method is applied to hair and fabric conditioners. 相似文献
79.
80.