A thermotolerant Aspergillus fumigatus strain isolated from composting pile of mixed industrial waste was found to produce a spectrum of cellulase and hemicellulases
when cultured on rice straw solidified substrate. The two-dimensional electrophoresis (2DE) resolved the secretome into 57
distinct protein spots. The zymograms developed against 2DE gels identified the presence of three β-glucosidases and five
CBHI/EGI isoforms in the secretome. The peptide mass fingerprinting of 17 protein spots by liquid chromatography mass spectrometry
characterized the secretome into different glycosyl hydrolase families. The enzyme cocktail produced by A. fumigatus was capable of efficient hydrolysis of alkali pretreated rice straw (at 7% and 10% w/v) resulting in 95% and 91% saccharification, respectively. 相似文献
We employed the Density Functional Theory along with small basis sets, B3LYP/LANL2DZ, for the study of FeTIM complexes with different pairs of axial ligands (CO, H2O, NH3, imidazole and CH3CN). These calculations did not result in relevant changes of molecular quantities as bond lengths, vibrational frequencies and electronic populations supporting any significant back-donation to the carbonyl or acetonitrile axial ligands. Moreover, a back-donation mechanism to the macrocycle cannot be used to explain the observed changes in molecular properties along these complexes with CO or CH3CN. This work also indicates that complexes with CO show smaller binding energies and are less stable than complexes with CH3CN. Further, the electronic band with the largest intensity in the visible region (or close to this region) is associated to the transition from an occupied 3d orbital on iron to an empty π∗ orbital located at the macrocycle. The energy of this Metal-to-Ligand Charge Transfer (MLCT) transition shows a linear relation to the total charge of the macrocycle in these complexes as given by Mulliken or Natural Population Analysis (NPA) formalisms. Finally, the macrocycle total charge seems to be influenced by the field induced by the axial ligands. 相似文献
The electrophilic activation(C-H activation) of alkenes by transition metal catalysts is a fundamental step in a rapidly growing number of catalytic processes since it would provide simple, clean, and economic methods for making controlled and selectively functionalized organic moieties directly from simple olefins. Also catalytic activation of C-H bonds leading to useful organic reactions such as new C-C, C-N and C-O bond formation is of considerable interest for the chemical and pharmaceutical industries and remained a long-term challenge to chemists. A substantial progress has made in the last decade in this area. Contrary to traditional belief, it is nowadays possible to control the regiochemistry of various additions of nucleophiles to alkenes by the choice of transition metal catalysts. Atom economy, an inevitable factor of current research also can be accomplished in these reactions. Developments in this area of selective hydrofunctionalisation of alkenes by taking into consideration of the mechanistic aspects and the role of organometallic catalyst or active species formed during the reaction on the outcome of the reactions are reviewed. 相似文献
Studies from authors’ group (at the University of Tennessee) on alkylidene complexes and α-H migration in alkyl alkylidyne complexes, leading to unusual tautomerization equilibria between bis-alkylidenes and alkyl alkylidynes, are reviewed. Preparation of silyl alkylidene complexes (Me3ECH2)2Ta(CHEMe3)(SiR3) [R3 = (SiMe3)3, E = C, 3a, Si, 3b; R3 = ButPh2, E = C, 4a, Si, 4b] and the pathway in the formation of 3b are discussed first. Pathways in the formation of archetypical Schrock-type alkyl alkylidenes (Me3ECH2)3TaCHEMe3 (E = C, 5a; Si, 5b), including the work using Ta(CD2CMe3)5 (21-d10) to confirm that it is the precursor to (Me3CCD2)3TaCDCMe3 (5a-d7), are then considered. Tautomerization of silyl alkylidyne (Me3CCH2)2W(CCMe3)(SiButPh2) (6a) with bis-alkylidene (Me3CCH2)W(CHCMe3)2(SiButPh2) (6b) as well as (Me3SiCH2)3W(CSiMe3)(PR3) [R3 = Me3, 7a; Me2Ph, 8a; Me2(CH2)2PMe2 (DMPE-P), 9a] with (Me3SiCH2)2W(CHSiMe3)2(PR3) (R3 = Me3, 7b; Me2Ph, 8b; DMPE-P, 9b) [P refers to a dangling P atom in Me2P(CH2)2PMe2] is covered next. Finally the conversion of the tungsten phosphine tautomerization mixtures to alkyl alkylidene alkylidyne (Me3SiCH2)W(CHSiMe3)(CSiMe3)(PR3)2 [(PR3)2 = (PMe3)2, 10; (PMe2Ph)2, 11; DMPE, 12], including its pathway, is presented. 相似文献
A catalyst system formed in situ from bis(2-methallyl)cycloocta-1,5-diene-ruthenium(II) [(cod)Ru(met)2], 1,4-bis(dicyclohexylphosphino)butane (dcypb) and ytterbium(III) triflate hydrate (Yb(OTf)3) was found to catalyze the addition of nitrogen nucleophiles to terminal alkynes under mild conditions to stereoselectively form the Z-enamide or Z-enimide products. Various secondary amides and imides could be added across the triple bond of a range of aliphatic and aromatic alkynes. The new bimetallic catalyst system sets new standards with regard to scope and selectivity for the synthesis of Z-configured anti-Markovnikov enamides. 相似文献
A novel polyamino polycarboxylic pyridine derivative ligand, N,N,N1,N1-(2,6-bis((3-(aminoethyl)-5-methyl-1H-pyrazol-1-yl)methyl)pyridine)hexakis(acetic acid) (L), was designed and synthesized with the motive that it is able to sensitize the emission of lanthanides. Its corresponding Eu(III) and Tb(III) complexes Na4EuLCl3·3H2O and Na4TbLCl3·5H2O were successfully prepared. The ligand and the complexes were characterized by elemental analysis, IR, MS, NMR and TG-DTA. The luminescence properties of the compounds in solid state were investigated; each complex had very narrow emission bands and strong luminescence intensity up to about 10,000. The TG-DTA studies showed that the initial decomposition temperature of both complexes was over 250 °C, elucidating the complexes had a high thermal stability. Meanwhile, the comparison with similar complexes suggested that the ligand with more coordination sites possessed more efficient antenna effect. To explore the potential medicinal value of L, the binding interaction of L and bovine serum albumin (BSA) was carried out by fluorescence spectrum. The studies indicated that the reaction between L and BSA was a static quenching procedure. The binding site number n and binding constant Ka were calculated according to the double logarithm regression equation. The thermodynamic parameters showed the Van der Waals and hydrogen bond interactions were the mainly impulse to the reaction. 相似文献
Drug targeting using magnetic nanoparticles (MNPs) under the action of an external magnetic field constitutes an important mode of drug delivery. Low cargo capacity, particularly in hydrophobic drugs, is one limitation shown by MNPs. This article describes a simple strategy to enhance the drug-loading capacity of MNPs. The approach was to use polymer-drug conjugates to modify MNPs by layer-by-layer assembly (LbL). Curcumin (CUR) has shown remarkably high cytotoxicity toward various cancer cell lines. However, the drug shows low anticancer activity in vivo because of its reduced systemic bioavailability acquired from its poor aqueous solubility and instability. To address this issue, we synthesized cationic and anionic CUR conjugates by anchoring CUR onto poly(vinylpyrroidone) (PVP-Cur) and onto hyaluronic acid (HA-Cur). We used these oppositely charged conjugates to modify MNPs by layer-by-layer (LbL) assembly. Six double layers of curcumin conjugates were constructed on positively charged amino-terminated magnetic nanoparticles, TMSPEDA@MNPs. Finally, HA was coated onto the outer surface to form HA (HA-Cur/PVP-Cur)(6)@MNPs. Cellular viability studies showed the dose-dependent antiproliferative effect of HA (HA-Cur/PVP-Cur)(6)@MNPs in two cancer cell lines (glioma cells and Caco-2 cells). HA (HA-Cur/PVP-Cur)(6)@MNPs exhibited more cytotoxicity than did free curcumin, which was attributed to the enhanced solubility along with better absorption via hyaluronic acid receptor-mediated endocytosis. Flow cytometry showed enhanced intake of the modified MNPs by cells. Confocal microscope images also confirmed the uptake of HA (HA-Cur/PVP-Cur)(6)@MNPs with greater efficacy. Thus, the strategy that we adopted here appears to have substantial potential in carrying enhanced payloads of hydrophobic drugs to specified targets. 相似文献
Iron phthalocyanine with iron sulfate has been successfully applied for high chemo- and regioselective reduction of aromatic nitro compounds to give the corresponding amines in a green solvent system without using any toxic ligand. The catalytic systems were also compatible with a large range of other reducible functional groups, such as keto, acid, amide, ester, halogen, lactone, nitrile, N-benzyl, O-benzyl, hydroxy, and heterocycles. In the present study, dinitro compounds have been regioselectively reduced to the corresponding amines with high yield. In most of the cases the conversion and selectivity was greater than 99% as determined by GC-MS analysis. 相似文献
A series of five new terbium(III) ion complexes with 4,4-difluoro-1-phenylbutane-1,3-dione (HDPBD) and anciliary ligands was synthesized. The composition and properties of complexes were analyzed by elemental analysis, IR, NMR, powder X-ray diffaraction, TG-DTG and photoluminescence spectroscopy. These complexes exhibited ligand sensitized green emission at 546 nm associated with 5D4?→?7F5 transitions of terbium ion in the emission spectra. The photoluminescence study manifested that the organic ligands act as antenna and facilitate the absorbed energy to emitting levels of Tb(III) ion efficiently. The enhanced luminescence intensity and decay time of ternary C2-C5 complexes observed due to synergistic effect of anciliary ligands. The CIE color coordinates of complexes came under the green region of chromaticity diagram. The mechanistic investigation of intramolecular energy transfer in the complexes was discussed in detail. These terbium(III) complexes can be thrivingly used as one of the green component in light emitting material and in display devices.