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1.
Panagiota Diamantopoulou Seraphim Papanikolaou Maria Kapoti Michael Komaitis George Aggelis Antonios Philippoussis 《Applied biochemistry and biotechnology》2012,167(3):536-551
The effect of four synthetic media containing glucose (initial concentration 30?g?l?1) on mycelial growth, exopolysaccharides (EPS) and cellular lipids production was examined in 11 mushroom species after 12 and 16?days of culture in static- and shake-flasks. Fatty acid analysis of cellular lipids produced was also performed. Agitation had a positive effect on biomass production, glucose consumption and lipid biosynthesis. Media that favoured the production of biomass were not suitable for EPS biosynthesis and vice versa. Biomass values varied from ??1.0?g?l?1 (Lentinula edodes) to ??19?g?l?1 (Pleurotus ostreatus), while the highest EPS quantity achieved ranged between 1.6 and 1.8?g?l?1 (for Ganoderma lucidum and L. edodes, respectively). Quantities of total cellular lipids varied between 2.5 and 18.5?% w/w, in dry mycelial mass for the fungi tested. Lipid in dry weight values were influenced by the medium composition. Cellular lipids presented noticeable quantities of poly-unsaturated fatty acids like linoleic acid. Compared to most of the mushrooms tested, lipids of Volvariella volvacea were more saturated. The ability of several mushroom species of our study to produce in notable quantities the above-mentioned added-value compounds renders these fungi worthy for further investigations. 相似文献
2.
AbstractPhytochemical investigation of the fruiting body of Volvariella volvacea led to the isolation of a new furanone, 2(5H)-furanone-4-propionic acid named volvafuranone A (1), together with twelve known compounds (2–13). Compounds 2–7, 9–11 were isolated from this mushroom for the first time. The isolated compounds were assessed for their cytotoxicity against four human tumour lines (SGC-7901, PC-3M, MCF-7, HepG-2), and the results showed that compound 2, 3, 12, 13 have significant cytotoxicity with IC50 values of 5.90?μM (HepG-2), 20.72?μM (HepG-2), 27.98?μM (PC-3M) and 23.15?μM (PC-3M), respectively. 相似文献
3.
《Journal of membrane science》1997,123(1):133-142
Two homologous series of nonionic surfactants, namely Rhom and Haas' tritons (alkylphenol ethoxylates) and Shell dobanols (dobanol ethoxylates) were used to characterize surface properties of ultrafiltration membranes. Static adsorption experiments were carried out to reveal the interactions developed between the membrane and the nonionic surfactant. The surfactant adsorption on the membranes depends on the chemical composition and structure of both the membranes and the surfactants used, as both chemical composition and structure determine the type of interactions controlling this adsorption illustrated on the adsorption isotherms. Distinct different behaviour was exhibited by four types of membranes of the same nominal molecular weight cut-off. The influence of pH and ionic strength was studied also. 相似文献
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5.
Jens M. Sørensen Thomas Magnussen Peter Rasmussen Aage Fredenslund 《Fluid Phase Equilibria》1979,3(1):47-82
The correlation of liquid—liquid equilibrium data using models for the liquid phase activity coefficients — for example NRTL and UNIQUAC — is reviewed. Different numerical procedures used in the computation of liquid—liquid equilibrium compositions on the basis of these models are evaluated. Methods for obtaining parameters from liquid—liquid equilibrium data are described, and a method leading to improved representation of tie lines using relatively few parameters is recommended. The NRTL and UNIQUAC equations are compared with respect to their ability of representing binary and ternary liquid—liquid equilibrium data. The UNIQUAC equation appears to be more convenient to use and to correlate the data slightly better than does NRTL with the same number of parameters. 相似文献
6.
Dr. Lan Liu Yu Bai Nian Sun Li Xia Prof. Todd L. Lowary Prof. John S. Klassen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(38):12059-12067
The interactions between 3‐O‐methyl‐mannose polysaccharides (MMPs), extracted from Mycobacterium smegmatis (consisting of a mixture of MMP‐10, ‐11, ‐12 and ‐13) or obtained by chemical synthesis (MMP‐5s, ‐8s, ‐11s and ‐14s), and linear saturated and unsaturated fatty acids (FAs), and a commercial mixture of naphthenic acids (NAs) in aqueous solution at 25 °C and pH 8.5 were quantified by electrospray ionization mass spectrometry (ESI‐MS). Association constants (Ka) for MMP binding to four FAs (myristic acid, palmitic acid, stearic acid and trans‐parinaric acid) were measured by using an indirect ESI‐MS assay, the “proxy protein” method. The Ka values are in the 104–105 M ?1 range and, based on results obtained for the binding of the synthetic MMPs with palmitic acid, increase with the size of the carbohydrate. Notably, the measured affinity of the extracted MMPs for trans‐parinaric acid is two orders of magnitude smaller than the reported value, which was determined by using a fluorescence assay. Using a newly developed competitive binding assay, referred to as the “proxy protein/proxy ligand” ESI‐MS method, it was shown that MMPs bind specifically to NAs in aqueous solution, with apparent affinities of approximately (5×104) M ?1 for the mixture of NAs tested. This represents the first demonstration that MMPs can bind to hydrophobic species more complex than those containing linear alkyl/alkenyl chains. Moreover, the approach developed here represents a novel method for probing carbohydrate–lipid interactions. 相似文献
7.
It is proposed to study the influence of interresidue H-bonds on the structure and properties of polysaccharides by comparing them to a series of systematically modified oligosaccharide analogues where some or all of the glycosidic O-atoms are replaced by buta-1,3-diyne-1,4-diyl groups. This group is long enough to interrupt the interresidue H-bonds, is chemically versatile, and allows a binomial synthesis. Several approaches to the simplest monomeric unit required to make analogues of cellulose are described. In the first approach, allyl α-D -galactopyranoside ( 1 ) was transformed via 2 and the tribenzyl ether 3 into the triflate 4 (Scheme 2). Substitution by cyanide (→ 5–7 ) followed by reduction with DIBAH led in high yield to the aldehyde 9 , which was transformed into the dibromoalkene 10 and the alkyne 11 following the Corey-Fuchs procedure (Scheme 3). The alkyne was deprotected via 12 or directly to the hemiacetal 13 . Oxidation to the lactone 14 , followed by addition of lithium (trimethylsilyl)acetylide Me3SiC?CLi/CeCl3 (→ 15 ) and reductive dehydroxylation afforded the disilylated dialkyne 16 . The large excess of Pd catalyst required for the transformation 11 → 13 was avoided by deallylating the dibromoalkene 10 (→ 17 → 18 ), followed by oxidation to the lactone 19 , addition of Me3SiC?CLi to the anomeric hemiketals 20 (α-D /β-D 7:2), dehydroxylation to 21 , and elimination to the monosilylated dialkyne 22 (Scheme 3). In an alternative approach, treatment of the epoxide 24 (from 23 ) with Me3SiC?CLi/Et2AlCl according to a known procedure gave not only the alkyne 27 but also 25 , resulting from participation of the MeOCH2O group (Scheme 4). Using Me3Al instead of Et2AlCl increased the yield and selectivity. Deprotection of 27 (→ 28 ), dibenzylation (→ 29 ), and acetolysis led to the diacetate 30 which was partially deacetylated (→ 31 ) and oxidized to the lactone 32 . Addition of Me3SiC?CLi/TiCl4 afforded the anomeric hemiketals 33 (α-D /β-D 3:2) which were deoxygenated to the dialkyne 34 . This synthesis of target monomers was shortened by treating the hydroxy acetal 36 (from 27 ) with (Me3SiC?C)3Al (Scheme 5): formation of the alkyne 37 (70%) by fully retentive alkynylating acetal cleavage is rationalised by postulating a participation of HOC(3). The sequence was further improved by substituting the MeOCH2O by the (i-Pr)3SiO group (Scheme 6); the epoxide 38 (from 23 ); yielded 85% of the alkyne 39 which was transformed, on the one hand, via 40 into the dibenzyl ether 29 , and, on the other hand, after C-desilylation (→ 41 ) into the dialkyne 42 . Finally, combined alkynylating opening of the oxirane and the 1,3-dioxolane rings of 38 with excess Et2Al C?CSiMe3 led directly to the monomer 43 which is thus available in two steps and 77% yield from 23 (Scheme 6). 相似文献
8.
The liquid chromatographic separation of 19 monoaromatic chlorophenols on a beta-cyclodextrin bonded-phase column is investigated in both an isocratic and a gradient elution mode. Even though the isocratic mode can be employed for the separation of the member components of each category of chlorophenols (e.g., mono-, di-, etc.), significant overlaps between the retention times of the various categories prevent the separation of all chlorophenols on a single chromatogram. Gradient elution can be used, however, for the separation of 15 of the 19 chlorophenol isomers. The unique features of gradient elution as applied to beta-cyclodextrin bonded-phase columns are discussed. The detection of chlorophenols with UV and electrochemical methods is also discussed and the two are compared. 相似文献
9.
The electronic structure of quadricyclane and 3-methylidenequadricyclane obtained by photoelectron spectroscopy, is used as a basis for the discussion of cycloadditions to these systems. The electronic structure of 3-heteroquadricyclanes, arrived at by theoretical calculations, agrees well with that expected from the above measured systems. A surprising outcome is that the orbital most responsible for the observed 2,4-cycloadditions to these heterosystems in not the HOMO but the third highest orbital which lies well below the former. This strongly suggests that these 2,4-cycloadditions proceed not in a concerted fashion but presumably involve as rate-determining step the formation of a resonance-stabilized zwitterionic intermediate. The nature of this intermeiate is discussed and the feasability of its formation investigated on the basis of thermochemical considerations. 相似文献
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Thermolysis of the 1,2-bis(glucosylalkynyl)benzenes 6 and 16 was studied to evaluate the effects of intramolecular H-bonding on the activation energy of the Bergman-Masamune-Sondheimer cycloaromatization, and to evaluate the use of the cycloaromatization for the synthesis of di-glycosylated naphthalenes. The dialkynes were prepared by cross-coupling of the O-benzylated or O-silylated glucosylalkynes 1 and 4 (Scheme 1). Thiolysis of the known 1 , or acetolysis of 1 , followed by deacetylation ( →2→3 ) and silylation gave 4 . Cross-coupling of 1 or 4 with iodo- or 1,2-diiodobezene depended upon the nature of the added amine and on the protecting group, and led to the mono- and dialkynylbenzenes 5 and 6 , or 12, 13 , and 15 , respectively. The benzyl ethers 5 and 6 gave poor yields upon acetolysis catalyzed by BF3 · OEt2, while Ac2O/CoCl2 · 6 H2O transformed 6 in good yields into the regioselectively debenzylated 10 . Desilylation of 7 and 13 gave the alcohols 8 and 14 , respectively. Thermolysis of 6 in PhCl gave 22 and 23 , independently of the presence or absence of 1,4-cyclohexadiene; 23 was formed from 22 (Scheme 2). Acetolysis of 22 gave the hexaacetate 24 that was completely debenzylated by thiolysis, yielding the diol 26 and trans-stilbene, evidencing the nature and position of the bridge between the glucosyl moieties (Scheme 3). Thiolysis of 22 yielded the unprotected 2,3-diglucosylnaphthalene 28 , a new type of C-glycosides. Depending upon conditions, hydrogenation of 22 led to 29 (after acetylation), 30 , or 32 . NMR and particularly NOE data evidence the threo-configuration of the bridge. The structure of 23 was confirmed by hydrolysis to the diol 34 and diphenylacetaldehyde, and by correlation of 23 with 22 via the common product 31 . Formation of 22 is rationalized by a Bergman cyclization to a diradical, followed by regioselective abstraction of a H-atom from the BnO? C(2) group, and diastereoselective combination of the doubly benzylic diradical (Scheme 4). While thermolysis of 3 in EtOH sets in around 140°, 16 did not react at 160° and decomposed at 180–220°. No evidence for intramolecular H-bonds of 16 , as compared to 14 , were found. 相似文献
12.
The Me3Si? C(1) bond of the bis-(trimethylsilyl)ethynylated anhydroalditol 2 is selectively cleaved with BuLi to yield 3 / 4 , while AgNO2/KCN in MeOH cleaves the Me3Si? C(2′) bond, leading to 5 (Scheme 1). Both Me3Si groups are removed with NaOH in MeOH (→ 7 ), the (i-Pr)3Si group is selectively cleaved with HCl in aq. MeOH ( → 6 ); all silyl substituents are removed with Bu4NF ( → 8 ). Acetolysis transformed 9 into 13 , which was desilylated to 14 , while thiolysis of 9 led to a mixture 11 / 12 . The tetraacetate 14 has also been obtained from 9 via 10 . Oxidative dimerisation of either 3 or 5 , or of a mixture 3 / 5 yields only the homodimers 15 and 16 (Scheme 2); treatment of 16 with AgNO2/KCN yielded 17 , deprotection proceeding much more slowly than the cleavage of the Me3Si? C(2′) group of 2 . The iodoalkyne 20 , required for the cross-coupling with 5 according to Cadiot-Chodkiewicz, was prepared by deprotection of 3 / 4 to 18 , methoxymethylation (→ 19 ), and iodination. Cross-coupling yielded mostly 21 , besides the homodimer 22 . Similarly, cross-coupling of 20 and 23 (obtained from 5 ) led to 24 and 22 . The structure of 24 was established by X-ray analysis (Fig.), showing a C(6)–C(5′) distance of 5.2 Å. The conditions for deprotecting 2 were applied to 21 , and led to 25 (AgNO2/KCN), 26 (aq. NaOH), 27 (Bu4NF), and 29 (HCl/MeOH; Scheme 3). Attempted deprotection of the propargylic-ether moiety with BuLi, however, failed. The dimer 27 was further deprotected to 28 . Acetolytic (Ac2O/Me3SiOTf) debenzylation of the dimer 30 , obtained from 10 , gave 31 (83%) which was deacetylated to 32 (Scheme 4). Cross-coupling of 5 and the bromoalkyne 33 , obtained from 10 , yielded 34 ; again, acetolysis proceeded well, leading to 35 . The cellobiose derivative 38 was prepared from the lactone 36 via 37 . The glycosidic linkage of 38 proved resistant to the conditions of acetolysis, leading to 39 . Acetolysis of the benzylated thiophene 40 (from 30 with Na2S) yielded the octaacetate 41 , but proceeded in substantially lower yields (50%). 相似文献
13.
F. Rodante S. Vecchio G. Catalani M. Guidotti 《Journal of Thermal Analysis and Calorimetry》2000,60(2):605-622
The thermal behaviour of some commercial pesticides was studied by simultaneous TG/DSC measurements. Kinetic parameters, related
to solid-gas phase transition processes, were also carried out by using dynamic TG technique.
The kinetics were analysed by using Arrhenius, Satava and Harcourt-Esson equations. The choice of the mathematical expression
to insert in these equations was influenced by the shape of the TG plot and other thermal analysis signals. The compounds
studied undergo a fusion process followed by a single vaporization process. The latter is well represented by a diffusive
process (D1, D2 or D3). The variation of the activation energy values within the range of temperature where the vaporization processes occur was
calculated. The enthalpy values of vaporization were also evaluated by using the Clausius-Clapeyron equation.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
14.
Bernard King 《Accreditation and quality assurance》2000,5(7):266-271
The paper (Parts I and II) reports the results of a survey carried out to assess the current situation in the field of metrology
in chemistry within Europe and to identify future needs for work at the European level. Responses to a questionnaire covering
17 economic sectors and distributed to 17 countries plus the European Commission Joint Research Centre (EC JRC), together
with input from a project group, EURACHEM and EUROMET, provided the basis of the study. Part I covers the protocol for the
study and reports current activities. Part II reports suggestions for future work, a strategy for metrology in chemistry and
recommendations for the EC Fifth Framework Programme. 相似文献
15.
Václav Kozmík Tomáš Hodík Vladimíra Novotná Damian Pociecha Ewa Gorecka 《Liquid crystals》2016,43(6):839-852
Five series of compounds based on 2,4- and 2,7-disubstituted benzothiophenes have been prepared and studied with respect to their mesomorphic properties. The molecular structure was modified by prolonging the molecular arms (varying the alkyl chain length) and orientation of the ester linkages. It was established that the transition temperatures and the type of the formed phases strictly depend on the ester orientation and only limited number of prepared compounds exhibited mesomorphic behaviour. Based on X-ray patterns, columnar phases were identified and found that they have centred crystallographic unit cell differing in the lattice parameters for homologous compounds. Although the bend angle of the studied materials is around 90° only, they exhibited formation of phases typical of the bent-shaped liquid crystals. 相似文献
16.
Ove Åström 《Analytica chimica acta》1977,88(1):17-23
An acid—base mixture is described which has linear pH response when titrated with strong base. The concentrations of the separate components in the mixture are given. Determinations of bases in the tange 0.05 M—0.25 M with a relative standard deviation of less than 0.5 % are reported. The method of preparing the mixture as well as some interferences of high salt concentrations in the sample are discussed. 相似文献
17.
Djakaou Iya-Sou Ghezzar Rédouane Mouffok Zekri Mohamed El-Mehdi Abdelmalek Fatiha Cavadias Simeon Ognier Stéphanie 《Plasma Chemistry and Plasma Processing》2015,35(1):143-157
Plasma Chemistry and Plasma Processing - The aim of this work is the modeling of plasma-chemical reactions taking place between highly oxidizing gaseous species (·OH, ·NO and... 相似文献
18.
Lipids of marine macrophytic algae. II. Fatty-acid and phospholipid composition of the chlorophyceae
V. M. Dembitskii O. A. Rozentsvet E. E. Pechenkina 《Chemistry of Natural Compounds》1990,26(3):336-337
Institute of the Ecology of the Volga Basin, USSR Academy of Sciences, Tol'yatti. Translated from Khimiya Prirodnykh Soedinenii,
No. 3, pp. 403–404, May–June, 1990. 相似文献
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The cross-coupling of the homopropargylic ether 1 and the halopropargylic ethers 2a and 2b was optimized, and aspects of the coupling mechanism were studied. Coupling promoted by Pd° and Cu1 in the presence of an amine yielded a mixture of the heterodimer 3 and the homodimers 4 and 5 (Scheme 1). Optimizations were first directed at suppressing homo-coupling. Homo-coupling is partially due to a H/I exchange ( 1 + 2a ? 6 + 7 ) promoted by CuI and an amine. The exchange, but not the formation of homodimers, was largely suppressed in DMSO. The influence of phosphine ligands was also evaluated. Weaker σ-donors (with the exception of PPh3) lead to a faster coupling and to a higher ratio of hetero- to homodimers, with P(fur)3 leading to the cleanest reaction. Homodimers are also formed (together with I2 · (i-Pr)2NH) by reductive dimerization of the iodoalkyne 2a in the presence of [Pd2(dba)3], CuI, and (i-Pr)2NH. Bulky and acceptor-substituted amines reduced the extent of the dimerization of 2a , but the bulkiest amines did not promote coupling. Better results were obtained by using the bromoalkyne 2b . Neither dimerization of 2b , nor H/Br exchange between 1 and 2b were observed. Coupling of 1 and 2b was slower than the one of 1 and 2a , but gave higher yields of the heterodimer 3 . The yield of 3 and the ratio of hetero-to homodimers was greatly improved by addition of LiI; no phosphine ligand is then required. While the oxidative addition of the iodoalkyne 2a to [Pd(PPh3)4] ( 2a → 8a ) was rapid, the one of the bromoalkyne 2b was much slower and proceeded via the η2-complex 9 as evidenced by 1H-NMR spectroscopy. The rearrangement of 9 to the bromopalladium σ-complex 8b follows first-order kinetics (k = 0.014 min?1). CuBr greatly increased the rate of this rearrangement. LiI caused rapid substitution of Br by I in the Pd σ-complex ( 8b → 8a ), but not in 9 , nor in 2b . The σ-complex 8a did not react with the alkyne 1 in the presence of (i-Pr)2NH, unless CuI was added. The alkynes 10 or 1 did not react with CuI and either TMEDA or (i-Pr)2NH to yield detectable amounts of the Cu-acetylides 11 or 12 . These observations are rationalized by the mechanism shown in Scheme 3, postulating the intermediacy of the binuclear alkyne-Pd-Cu complexes C and J , and some or all of E–H , and highlighting the role of CuI in this coupling. 相似文献