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71.
72.
As the first systematic study dealing with the adsorption of estrogens by granular activated carbon (GAC), the removal behavior of 17β-estradiol (E2) and its biotransformation product of estrone (E1) in fixed GAC columns was examined using four biological activated carbon (BAC) columns (BAC-1~BAC-4) generated by coating four GAC columns with detached microorganisms from the riverbed sediment of a representative drinking river water source containing lower content of natural organic matter (NOM). For comparison, parallel adsorption experiments were also performed using another four GAC columns (GAC-1~ GAC-4) packed by strictly following the configurations of four BAC columns. Adsorption experimental results obtained by intermittently spiking E2 over a total running period about 350 days into the river water mixed with or without a peaty water containing higher content of NOM showed that E2 was readily removed by adsorption and the combined adsorption/biodegradation. The vertical profiles of E2 and E1, which have great significance for better understanding and optimization of the adsorption process for removal of human estrogens, were also obtained. 相似文献
73.
Litseaone A, isolated from the stem barks of Litsea rubescens and Litsea pedunculata, is a chalcone derivative with a novel spiro-epoxide moiety. The structural revision of litseaone A was achieved by the racemic synthesis of the proposed structure and the asymmetric synthesis of the revised structure. The major tautomeric structure of litseaone A and the relative stereochemistry at the epoxide carbon center were also clarified. 相似文献
74.
Anomalous binding profile of phenylboronic acid with N-acetylneuraminic acid (Neu5Ac) in aqueous solution with varying pH 总被引:1,自引:0,他引:1
Otsuka H Uchimura E Koshino H Okano T Kataoka K 《Journal of the American Chemical Society》2003,125(12):3493-3502
Borates are known to interact with carbohydrate moieties expressed on the surface of biological membranes of a variety of cells, viruses, bacteria, and fungi. This study revealed the anomalous binding profile of borate in aqueous solution with N-acetylneuraminic acid (Neu5Ac, sialic acid) as a potential receptor site on the surfaces of biological membranes using (11)B, (1)H, (13)C, and (15)N nuclear magnetic resonance spectroscopies. 3-(Propionamido)phenylboronic acid (PAPBA) was chosen as the model borate compound. The equilibrium constant (K) for Neu5Ac binding to PAPBA was compared with those for glucose, mannose, and galactose, which are the major carbohydrate constituents of glycoproteins and glycolipids expressed on biological membranes. In the Neu5Ac/PAPBA system, the unusual pH dependency of the K values, a decrease in K with increasing pH, was observed, suggesting the formation of a trigonal-formed complex stabilized by the coordination of an amide group of Neu5Ac at the C-5 position to the boron atom, forming intramolecular B-N or B-O bonding. Furthermore, the anomalously high complexing ability at physiological pH 7.4 was confirmed for this system, with the K value 37.6 which is approximately 7 times higher than that for glucose. This exceptionally high value of K at physiological pH, compared to those of other sugars, strongly suggests that the boronic acid selectively recognizes the Neu5Ac residues of the glycosylated components including glycoproteins and gangliosides existing on the surface of the biological membranes. 相似文献
75.
[reaction: see text] The coupling reaction of germanium compounds with aryl halides has been developed. The Pd(0)-catalyzed reaction of aryl halides with tri(2-furyl)germane provides aryltri(2-furyl)germanes in good yield. The cross-coupling reaction of aryltri(2-furyl)germanes with aryl halides is achieved. This allows facile synthesis of unsymmetrical biaryls from two different aryl halides. 相似文献
76.
Tanaka H Sato N Matsuyama T 《Langmuir : the ACS journal of surfaces and colloids》2005,21(17):7696-7701
Poly(methyl acrylate)-grafted poly(methyl-n-propylsilane) (PMPrS-g-PMA) and poly(acrylic acid)-grafted PMPrS (PMPrS-g-PAA) were synthesized by gamma-ray-induced graft polymerization, and the association behavior of these graft copolymers was investigated in selective solvents composed of good and poor solvents for the PMPrS main chain. Fluorescence spectroscopy with perylene as a fluorescent probe revealed that PMPrS-g-PAA in a water/THF mixed solvent self-assembles into micelles with a swollen core of PMPrS chains in the water content range of 50-95%. UV spectroscopy demonstrated that a further increase of the water content gives rise to the conformational transition of the PMPrS chains in the micelle core from the random conformation to the conformation that corresponds to that in the solid state at a water content of ca. 95%, independent of the grafting yield. Similar behavior was also observed in DMSO/THF solutions of PMPrS-g-PMA, for which the conformational transition occurred at the constant DMSO content of ca. 95%. These results indicate that solvatochromic behavior of polysilane, which is a characteristic feature of polysilane, proved to provide information on the inner structure of those micelles: PMPrS chains in the core undergo conformational transition as the content of the poor solvents for PMPrS increases, while maintaining the micelle structure. 相似文献
77.
Synthesis of the proposed structure of tyroscherin, a growth inhibitor of IGF-1-dependent cancer cells, was succeeded by one-pot Julia coupling. However, spectral data of the synthetic compound were not identical with those of natural tyroscherin. The stereochemistry of tyroscherin is revised to be 2S,3R,8R,10R by syntheses of stereoisomers. Synthetic tyroscherin showed more potent activity than its stereoisomers against IGF-1-dependent cancer cells. 相似文献
78.
79.
Noncanonical RNA Nucleosides as Molecular Fossils of an Early Earth—Generation by Prebiotic Methylations and Carbamoylations 下载免费PDF全文
Christina Schneider Sidney Becker Dr. Hidenori Okamura Antony Crisp Dr. Tynchtyk Amatov Michael Stadlmeier Prof. Dr. Thomas Carell 《Angewandte Chemie (International ed. in English)》2018,57(20):5943-5946
The RNA‐world hypothesis assumes that life on Earth started with small RNA molecules that catalyzed their own formation. Vital to this hypothesis is the need for prebiotic routes towards RNA. Contemporary RNA, however, is not only constructed from the four canonical nucleobases (A, C, G, and U), it also contains many chemically modified (noncanonical) bases. A still open question is whether these noncanonical bases were formed in parallel to the canonical bases (chemical origin) or later, when life demanded higher functional diversity (biological origin). Here we show that isocyanates in combination with sodium nitrite establish methylating and carbamoylating reactivity compatible with early Earth conditions. These reactions lead to the formation of methylated and amino acid modified nucleosides that are still extant. Our data provide a plausible scenario for the chemical origin of certain noncanonical bases, which suggests that they are fossils of an early Earth. 相似文献
80.
We discuss a propositional logic which combines classical reasoning with constructive reasoning, i.e., intuitionistic logic augmented with a class of propositional variables for which we postulate the decidability property. We call it intuitionistic logic with classical atoms. We introduce two hypersequent calculi for this logic. Our main results presented here are cut-elimination with the subformula property for the calculi. As corollaries, we show decidability, an extended form of the disjunction property, the existence of embedding into an intuitionistic modal logic and a partial form of interpolation. 相似文献