Aromatic polyketide glycosides from an entomopathogenic fungus,Cordyceps indigotica

A new aromatic polyketide glycoside, indigotide A (1), was isolated from the culture broth of the entomopathogenic fungus, Cordyceps indigotica, along with known cyclic depsipeptides, destruxins A, A₂, B, B₂ and E (3–7), and a polyketide, NG-393 (8). Repeated treatment of the C. indigotica culture broth with 5-azacytidine, a DNA methyltransferase inhibitor, led to the isolation of another new aromatic polyketide glycoside, indigotide B (2).     

A new azaphilone from the entomopathogenic fungus Hypocrella sp.

This report describes the isolation of a new azaphilone, designated hypocrellone A (2), together with five known compounds (1, 3–6) from a submerged culture of the entomopathogenic fungus Hypocrella sp. (isolate WYTY-21). The absolute stereostructures of the two compounds (1 and 2) were elucidated based on 1D and 2D NMR spectroscopic and mass spectrometric data combined with the data from various chemical transformations. Hypocrellone A (2) and three (3–6) of the five known compounds were cytotoxic to hepatoma cells (cell line BEL-7404); IC₅₀ values ranged from 6.2 to 17.4 μM. At 200 μM, none of the six compounds was toxic to normal human liver cells (cell line HL-7702) or to normal human kidney epithelial cells (cell line HEK-293T).     

Dihydrobenzofurans as cannabinoid receptor ligands from Cordyceps annullata,an entomopathogenic fungus cultivated in the presence of an HDAC inhibitor

The secondary metabolite production of Cordyceps annullata, an entomopathogenic fungus, was clearly enhanced by the addition of suberoyl bis-hydroxamic acid (SBHA), a histone deacetylase (HDAC) inhibitor, to the culture medium. Four new 2,3-dihydrobenzofurans, annullatins A–D (1–4), and a new aromatic polyketide, annullatin E (5) were isolated from the culture medium, and the structures, including the absolute stereochemistries, were determined by spectroscopic analysis, vibrational circular dichroism (VCD), and chemical transformations. Annullatin A (1) exhibited potent agonistic activity toward the cannabinoid receptors CB1 and CB2. Annullatin B (2) and D (4) displayed CB1 agonistic activity and CB2 inverse agonistic activity.     

Chromatomembrane gas extraction generation of standard gas mixtures using composite carbon-fluoroplastic matrices

A procedure is proposed for the generation of standard gas mixtures of volatile organic substances based on chromatomembrane gas extraction with the use of composite carbon-fluoroplastic matrices. The regularities of this process were found, and an adequate physicochemical model was developed. The advantages of the proposed procedure over traditional bubbling and chromatomembrane gas extraction on unmodified matrices were demonstrated.     

A novel carbon skeletal trichothecane, tenuipesine A, isolated from an entomopathogenic fungus, Paecilomyces tenuipes

Tenuipesine A (1), a novel trichothecane with an unprecedented carbon-migrated skeleton that embodies of a cyclopropane ring, was isolated from cultivated fruiting bodies of Paecilomyces tenuipes (Isaria japonica), a popular entomopathogenic fungi employed in folk medicine and health foods in China, Korea, and Japan. The structure was determined on the basis of two-dimensional NMR data. Its stereochemistry was elucidated by spectroscopic data and the chemical transformation of the coexisting trichothecene, 4beta-acetoxy-12,13-epoxytrichothec-9-ene-3alpha,15-diol (2). [structure: see text]     

Laponite clay in homopolymer and tri-block copolymer matrices

Macromolecule/laponite nanomaterials were studied by DSC and X-ray diffraction techniques. The matrices are poly(ethylene) glycols at various molecular masses and poly(ethylene oxides)-poly(propylene oxides)-poly(ethylene oxides) tri-block copolymers. The latter were tuned by modulating the molecular masses, at constant hydrophilic/hydrophobic ratio, and the hydrophilicity. For all the investigated systems, the enthalpy of melting (ΔH _m) is nearly constant up to a given composition thereafter it increases monotonically reaching the value of the pure macromolecule. We proposed a model to interpret the DSC data. Briefly, it was invoked a mechanism of interaction following which some segments of the adsorbed macromolecule are anchored to the laponite (RD) particles and the remaining segments are radiating away from the surface. The portion of the macromolecule in contact with RD does not contribute to ΔH _m whereas that radiating away from the clay does. Once that the RD surface is saturated, the excess of the macromolecule behaves like the pure one. The proposed model allowed to compute successfully the ΔH _m values. The X-ray diffraction experiments ruled out the polymer intercalation between the silicate sheets.     

Akanthomycin, a new antibiotic pyridone from the entomopathogenic fungus Akanthomyces gracilis

[structure: see text] Organic extracts of the entomopathogenic fungus Akanthomyces gracilis ARS 2910 contained antibiotics active against Staphylococcus aureus. Bioassay-guided fractionation of the CH2Cl2 extract yielded the antibacterial compound akanthomycin as a mixture of atropisomers along with the closely related compounds 8-methylpyridoxatin and cordypyridone C. Akanthomycin was characterized using X-ray crystallography and NMR.     

Aromatic polyketide production in Cordyceps indigotica, an entomopathogenic fungus, induced by exposure to a histone deacetylase inhibitor

Cultivation of Cordyceps indigotica, an entomopathogenic fungus, in the presence of suberoyl bis-hydroxamic acid (an HDAC inhibitor) greatly activated its polyketide synthesis apparatus to afford six novel aromatic polyketides, indigotides C-F (1-4), 13-hydroxyindigotide A (5), and 8-O-methylindigotide B (6). The structures of these compounds were determined by NMR spectroscopic analyses. Among the compounds, indigotides C-E (1-3) possessed unprecedented dimeric polyketide frameworks possibly generated via a [4 + 2] cycloaddition or Michael type reaction.     

Hydrophobic and electrostatic cell surface properties of blastospores of the entomopathogenic fungus Paecilomyces fumosoroseus

The physicochemical surface properties of blastospores of the entomopathogenic fungus Paecilomyces fumosoroseus were examined. Contact angle measurements were performed on microbial lawns composed of blastospores of P. fumosoroseus to quantify their cell surface energy components. In addition, suspensions of the blastospores were characterized with the microbial adhesion to solvents assay. Zeta potential measurements were used to quantify the surface charge and determine the zero potential of the blastospores. The results show blastospores of P. fumosoroseus are best described as having a basic monopolar surface and classified as hydrophilic. Blastospores are also negatively charged under neutral conditions with an isoelectric point of 3.4.     

Thermal properties of clay containing polymeric reinforcement as an eco-friendly bio-insulation composite for buildings

Journal of Thermal Analysis and Calorimetry - Polymer/clay-based composites were prepared via solution intercalation method using natural clay and poly (ethylene) glycol (PEG4000) as organic...     

Modeling Young’s modulus of rubber–clay nanocomposites using composite theories

The modulus reinforcement of rubber–clay nanocomposites was examined using Guth, Halpin–Tsai and the modified Halpin–Tsai equations, which are universally used for composites reinforced by fiber-like or rod-like fillers. Taking account of the lower contribution of the platelet-like filler to Young’s modulus than that of the fiber-like filler, the modulus reduction factor (MRF) for the platelet-like fillers of 0.66, determined by fitting experimental data, is introduced into the above three equations. The aspect ratios of clay platelets in rubber–clay nanocomposites were determined by statistically analyzing TEM micrographs. The predicting ability of the above three equations for polymer–clay nanocomposites is improved by introducing MRF.     

Hydroformylation of olefins catalyzed by rhodium complex anchored on clay matrices

Investigations on the catalytic activity of a transient Rh(I) triphenylphosphine complex1 anchored on montmorillonite clay have been carried out with respect to hydroformylation of olefins at 70°C and 60 atm of CO+H₂ (1:1). The analysis has shown that aldehydes and hydrocarbons of the corresponding olefins result under hydroformylation conditions. In limonene, reaction proceeds with double hydroformylation and hydrogenation to give the respective oxo products. The catalytic activities of1 are compared with Wilkinson's Rh^I (H) (CO) (PPh₃)₂ (6) complex in solution under the same hydroformylation conditions.     

Cure behavior and thermal stability of an epoxy: new bismaleimide blends for composite matrices

A new bismaleimide (BMI) resin was synthesized to formulate epoxy(tetraglycidyl diaminodiphenyl methane; TGDDM) – bismaleimide thermoset blends for composite matrix applications. 4,4′-diaminodiphenyl methane (DDM) was used as an amine curing agent for the TGDDM. A Fourier transform infrared (FTIR) spectroscopy was employed to characterize the new BMI resin. Cure behavior of the epoxy–BMI blends was studied using a differential scanning calorimeter (DSC). DSC thermograms of the thermoset blends indicated two exothermic peaks. The glass transition temperature of the thermoset blends decreased with BMI content. Thermogravimetric analysis (TGA) was carried out to investigate thermal degradation behavior of the cured epoxy–BMI thermoset blends. The new BMI resin reacted partially with the DDM and weak intercrosslinking polymer networks were formed during cure of the thermoset blends.     

Highly oxidized ergosterols and isariotin analogs from an entomopathogenic fungus,Gibellula formosana,cultivated in the presence of epigenetic modifying agents

The concomitant addition of a histone deacetylase inhibitor, suberoyl bis-hydroxamic acid, and a DNA methyltransferase inhibitor, RG-108, to the culture medium of Gibellula formosana, an entomopathogenic fungus, induced a significant increase in diversity of secondary metabolites. From the culture media were isolated two new highly oxidized ergosterols, formosterols A (1) and B (2), and five new isariotin analogs, 12′-O-acetylisariotin A (4), 1-epi-isariotin A (5), and isariotins K–M (6–8), together with 22,23-epoxy-3,12,14,16-tetrahydroxyergosta-5,7-dien-11-one (named formosterol C) (3), isariotins A (9), C (10), and E (11), TK-57-164A (12), and beauvericin (13). The NMR spectra, X-ray single crystallographic diffraction, and chemical transformations revealed the structures of the two new formosterols and five new isariotins. The stereochemistry of formosterol C (3) was deduced from its spectroscopic data. The side chains of formosterols A–C (1–3) contained cis-22,23-epoxide, which is rarely present in naturally occurring sterols and triterpenes.     

Novel cross-linked polyacrylamide matrices: an investigation using gradient gel electrophoresis

Gradient gel electrophoresis was used to examine the separation properties of novel cross-linking compounds for polyacrylamide (PAAm). At low %T and at the same %C protein migration difference is accentuated for bismethacrylamide cross-linked networks relative to bisacrylamide cross-linked networks. Similar properties were observed for cyclic monomers at low %T. This trend is maintained throughout the gradient. However, at higher %T migration differential relative to N,N'-methylenebisacrylamide (Bis) was less pronounced. Evidence from gradient gels suggests that reactivity and functionality of vinyl groups impose an overriding control over network formation.     

Gas transport properties of polypropylene/clay composite membranes

Polypropylene membranes modified with natural and organically modified montmorillonite clays were prepared. The permeability, diffusivity and solubility of helium, oxygen and nitrogen were determined for the unfilled and filled membranes over the temperature range 25-65 °C. Physical properties of polypropylene membranes were investigated using X-ray diffraction, thermogravimetric analyser, tensile testing and differential scanning calorimetry. The results showed that the filled membranes exhibit lower gas permeability compared to the unfilled polypropylene membrane. For helium, a reduced diffusivity is mainly responsible for the reduction in the permeability, in contrast, for nitrogen and oxygen, both diffusivity and solubility were reduced by the presence of fillers. The X-ray diffraction spectra showed that the incorporation of the unmodified and modified clay did not affect the crystallographic nature of polypropylene.     

Biosynthesis of the cyclooligomer depsipeptide beauvericin, a virulence factor of the entomopathogenic fungus Beauveria bassiana

Beauvericin, a cyclohexadepsipeptide ionophore from the entomopathogen Beauveria bassiana, shows antibiotic, antifungal, insecticidal, and cancer cell antiproliferative and antihaptotactic (cell motility inhibitory) activity in vitro. The bbBeas gene encoding the BbBEAS nonribosomal peptide synthetase was isolated from B. bassiana and confirmed to be responsible for beauvericin biosynthesis by targeted disruption. BbBEAS utilizes D-2-hydroxyisovalerate (D-Hiv) and L-phenylalanine (Phe) for the iterative synthesis of a predicted N-methyl-dipeptidol intermediate, and forms the cyclic trimeric ester beauvericin from this intermediate in an unusual recursive process. Heterologous expression of the bbBeas gene in Escherichia coli to produce the 3189 amino acid, 351.9 kDa BbBEAS enzyme provided a strain proficient in beauvericin biosynthesis. Comparative infection assays with a BbBEAS knockout B. bassiana strain against three insect hosts revealed that beauvericin plays a highly significant but not indispensable role in virulence.     

Conidial pigmentation is important to tolerance against solar-simulated radiation in the entomopathogenic fungus Metarhizium anisopliae

The importance of conidial pigmentation to solar UV radiation tolerance in the entomopathogenic fungus Metarhizium anisopliae var. anisopliae, was estimated by comparing the effects of exposure to simulated solar UV radiation on the wild-type parent strain U.S. Department of Agriculture (USDA)-Agricultural Research Service (ARS) Collection of Entomopathogenic Fungal Cultures (ARSEF) 23, which has dark green conidia, and three groups of color mutants with yellow, purple and white conidia. The comparisons included inactivation levels and the kinetics of germination of conidia exposed or not exposed to simulated solar UV radiation. In addition to significantly inactivating the conidia of different mutants, exposure to radiation delayed for several hours the germination of surviving conidia of the wild type and all mutants. In general, mutants with white conidia were more sensitive to simulated solar UV radiation than mutants with purple conidia, which were more sensitive than mutants with yellow conidia, which in turn were more sensitive than the green wild strain. A significant variation in tolerance to simulated solar radiation was observed among mutants within each color group, particularly among mutants with yellow conidia. Revertants with green conidia, DWR 179 and DWR 176, were obtained from the very sensitive UV mutants DWR 148 (yellow conidia) and DWR 149 (purple conidia), respectively. These revertants had levels of tolerance to simulated solar UV radiation similar to those of the wild-type ARSEF 23. This observation is strong evidence of the importance of green conidial pigmentation for tolerance to simulated solar UV radiation, a factor that could be manipulated to produce M. anisopliae strains with more tolerance to solar UV radiation.     

聚合物涂层光稳定化研究进展

用于改造各种材料的表面性质并防止其光老化的聚合物涂层的光稳定化技术近年来已经成为高分子材料科学和光化学领域的又一研究热点。本文以紫外光固化聚合物涂层为重点综述了该研究领域的发展过程、理论研究特点和应用技术的生长点,并对聚合物涂层光稳定化技术的最新进展进行了评述,讨论了聚合物涂层光稳定化技术中新型光固化树脂,多功能单体、光引发剂和光稳定剂（包括紫外吸收剂和受阻胺类稳定剂）的特点及作用机理。     

Photostabilization of recycled pigmented polypropylene crate material

The photostabilizing efficiencies of various light stabilizer systems in recycled pigmented polypropylene crate materials, previously in use for 6–7 years, have been examined using the standard carbonyl index and time to embrittlement methods. Thirty-two polymer film samples with and without additional stabilizer have been prepared and exposed in both a Xenotest-150 and Microscal apparatus. The performance of the various light stabilizer systems in both exposure units are compared and discussed.