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High Molecular Weight Compounds (high + molecular_weight_compound)
Selected AbstractsPotential mechanism for detection by Apis mellifera of the parasitic mite Varroa destructor inside sealed brood cellsPHYSIOLOGICAL ENTOMOLOGY, Issue 3 2002Caroline Martin Abstract The parasitic mite Varroa destructor Anderson & Trueman is a major pest of the honeybee Apis mellifera L. throughout the world. Chemical agents currently used for mite control leave contaminating residues and promote pesticide resistance. As an alternative means of control, it would be useful to identify natural substances enabling bees to detect Varroa inside brood cells. These substances could then be used to trigger mite hygienic behaviour by bees. In this study several techniques were used to screen substances that might allow detection of infested brood cells by bees. Gas chromatography-mass spectrometry analysis was performed on substances extracted in dichloromethane from the contents of brood cells. Solid phase microextraction and solid injection were performed on substances obtained from living and dead Varroa, respectively. Electroantennography was performed to assess the sensitivity of olfactory receptors in bee antennae to some of these substances. Principal component analysis based on proportions of cuticular substances allowed discrimination between bees and other cell contents. Foundress Varroa exhibited the greatest dissimilarity to healthy pupae that were used as controls. Immature Varroa and faecal material were intermediate. High molecular weight compounds, mainly dimethylalkanes, were proportionally the most characteristic components of foundress Varroa. This finding suggests that these compounds would be the most apt to induce uncapping of cells infested by Varroa. Solid-phase microextraction and solid injection demonstrated the presence of aliphatic acids, esters, and one alcohol, eicosenol, in Varroa. Electroantennographic recordings showed that mite-resistant bees were more responsive to some acids and one ester. We speculate that these compounds may be involved in recognition of living Varroa by honeybees. [source] Degradation and formation of polycyclic aromatic compounds during bioslurry treatment of an aged gasworks soilENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2003Staffan Lundstedt Abstract The goals of this study were to investigate the relative degradation rates of polycyclic aromatic compounds (PACs) in contaminated soil, and to assess whether persistent oxidation products are formed during their degradation. Samples were taken on five occasions during a pilot-scale bioslurry treatment of soil from a former gasworks site. More than 100 PACs were identified in the soil, including unsubstituted polycyclic aromatic hydrocarbons (PAHs), alkylated PAHs (alkyl-PAHs), heterocyclic PACs, and oxygenated PAHs (oxy-PAHs), such as ketones, quinones, and coumarins. During the treatment, the low molecular weight PAHs and heterocyclics were degraded faster than the high molecular weight compounds. The unsubstituted PAHs also appear to have degraded more quickly than the corresponding alkyl-PAHs and nitrogen-containing heterocyclics. No new oxidation products that were not present in the untreated soil were identified after the soil treatment. However, oxy-PAHs that were present in the untreated soil were generally degraded more slowly than the parent compounds, suggesting that they were formed during the treatment or that they are more persistent. Two oxidation products, 1-acenaphthenone and 4-oxapyrene-5-one, were found at significantly higher concentrations at the end of the study. Because oxy-PAHs can be acutely toxic, mutagenic, or carcinogenic, we suggest that this group of compounds should also be monitored during the treatment of PAH-contaminated soil. [source] Improved automated extraction and separation procedure for soil lipid analysesEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2004G. L. B. Wiesenberg Summary Analysis of soil lipids may contribute to an improved understanding of atmosphere to soil carbon fluxes, soil organic matter source differentiation and pollutant accumulation. Soil lipids, mostly originating from plants and microorganisms, have traditionally been analysed by non-automated extraction and separation methods, which produce several lipid fractions, operationally defined by polarity. Here we present a combination of fast, automated and reproducible techniques, adopted from organic geochemical studies, for preparative separation of individual soil lipid fractions with increasing polarity. These techniques involve commercially available instruments, including accelerated solvent extraction and a two-step automated medium-pressure liquid chromatography procedure. The method yields eight lipid fractions consisting of five fractions fully amenable to gas chromatography/mass spectrometry (GC/MS) (aliphatic hydrocarbons, aromatic hydrocarbons, ketones, alcohols, carboxylic acids), and three fractions of highly polar or high molecular weight compounds (bases, very long-chain wax esters (C40+), high polarity compounds) that were not measurable with GC/MS under standard conditions. We tested the method on five agricultural soils. Results show that (i) mass recoveries for the individual fractions are reproducible, (ii) within individual fractions compound distribution patterns are reproducible, as demonstrated for alkanes and carboxylic acids, and (iii) individual fractions represent distinct and clean compound classes, free of interfering substances detectable by GC/MS. Thus, automated separation can be a fast, effective and reproducible procedure for fractionation of complex mixtures of soil lipids into clean compound classes, directly suitable for a variety of molecular (e.g. GC/MS) and isotopic characterizations (e.g. gas chromatography coupled with isotope ratio monitoring mass spectrometry or accelerator mass spectrometry). [source] Starch-like exopolysaccharide produced by the filamentous fungi Ophiostoma ulmi and O. novo-ulmiFOREST PATHOLOGY, Issue 2 2007R. Jeng Summary This paper describes the chemical and biochemical properties of exopolysaccharides (EPS) produced by Ophiostoma ulmi and O. novo-ulmi isolates, the Dutch elm disease (DED) fungi. Some of EPS have been considered as pathogenicity factor in the DED complex. The selected isolates grow well and produce EPS in a medium containing various types of carbon and nitrogen sources. EPS obtained from potato dextrose broth (PDB) medium appeared to be opaque, firm and stained purple blue with iodine-potassium iodide solution, whereas those from yeast extract (YE) medium were less opaque, jelly-like and remained unchanged in iodine solution. The selected fungal isolates produced much higher molecular weight EPS from the medium containing YE than from PDB. The results of this study suggest that high molecular weight compounds produced by O. ulmi (W9) and O. novo-ulmi (R136) are not involved in DED pathogenesis. Spectrometric analysis of acid-digested EPS obtained from PDB and YE revealed the presence of a monomer similar to glucose used as a standard. Thin layer chromatography indicated that glucan-1,4- , -glucosidase (glucoamylase) only hydrolyses EPS from PDB media and releases glucose. The results strongly indicate that isolates of O. ulmi and O. novo-ulmi produce starch-like EPS from PDB medium. The EPS obtained from YE medium lacked this characteristic. The biological significance and the potential use of these EPS are discussed. [source] Hydrothermal processing of rice husks: effects of severity on product distributionJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2008Rodolfo Vegas Abstract BACKGROUND: Treatment in aqueous media (hydrothermal or autohydrolysis reactions) is an environmentally friendly technology for fractionating lignocellulosic materials. Rice husks were subjected to hydrothermal processing under a variety of operational conditions to cause the selective breakdown of xylan chains, in order to assess the effects of reaction severity on the distribution of reaction products. RESULTS: The effects of severity (measured by the severity factor, R0) on the concentrations of the major autohydrolysis products (monosaccharides, xylo- and glucooligosaccharides, xylooligosaccharide substituents, acetic acid, acid-soluble lignin and elemental nitrogen) were assessed. The interrelationship between the severity of treatment and molecular weight distribution was established by high-performance size-exclusion chromatography. Selected samples were subjected to refining treatments as ethyl acetate extraction and ion exchange for refining purposes, and the concentrates were assayed by high-performance anion-exchange chromatography and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. CONCLUSIONS The protein equivalent of the products present in liquors accounted for 43 to 51% of the protein present in the raw rice husks. The concentrations of glucose (derived from starchy material) and arabinose (split from the xylan backbone) were fairly constant with severity. Even in treatments at low severity, high molecular weight compounds derived from xylan accounted for a limited part of the stoichiometric amount. Operating under harsh conditions, about 50% of the total xylan-derived compounds corresponded to fractions with a degree of polymerization (DP) < 9. After refining, saccharides accounted for more than 90% of the non-volatile components of the sample. The refined products showed a series of xylose oligomers up to about DP 13, and a series of acetylated xylose oligomers up to about DP 15. Copyright © 2008 Society of Chemical Industry [source] ANTIMICROBIAL ACTIVITY OF MELANOIDINSJOURNAL OF FOOD QUALITY, Issue 2 2007JOSÉ A. RUFIÁN-HENARES ABSTRACT Melanoidins are high molecular weight compounds formed during the final stage of the Maillard reaction. Melanoidins have been studied in recent years because of their nutritional, biological and health implications, apart from their role on the stability during processing and shelf life of foods. A fast and robust microtiter plate-based assay for a quantitative screening of the antimicrobial activity of melanoidins was applied. Oxytetracyclin was used as reference for assessing the antimicrobial activity of different melanoidins isolated from model systems. The minimum inhibitory concentration was calculated, and activity was related to the antimicrobial activity of an oxytetracyclin solution (100 µg/L). Glucose,lysine melanoidin exerted the highest antimicrobial activity, being at a concentration of 1 mg/mL, equivalent to an oxytetracyclin solution of 170 µg/L. [source] A New Group Contribution Method based on Equation of State Parameters to Evaluate the Critical Properties of Simple and Complex MoleculesTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2006José O. Valderrama Abstract A new group contribution method to evaluate the critical properties (temperature, pressure and volume) is presented and applied to estimate the critical properties of biomolecules. Similar to other group contribution methods, the one proposed here divides the molecule into conveniently defined groups and evaluates the properties as the sum of the different contributions according to a specified model equation for each of the properties. The proposed method consists of a one-step calculation that uses simple model equations and does not require additional data besides the knowledge of the structure of the molecule, except for isomers. For these substances the normal boiling temperature, the molecular mass and the number of atoms in the molecule are used to distinguish among isomers. The method is applicable to high molecular weight compounds, as most biomolecules and large molecules present in natural products. On présente une nouvelle méthode de contribution de groupe pour évaluer les propriétés critiques (température, pression et volume) de biomolécules. Comme dans le cas d'autres méthodes de contribution de groupe, celle qu'on présente ici divise la molécule en groupes définis de manière pratique et évalue les propriétés comme la somme des différentes contributions selon une équation de modèle spécifique pour chacune des propriétés. La méthode proposée consiste en un calcul en une étape qui utilise des équations de modèle simple et, excepté pour les isomères, ne requiert pas de données supplémentaires hormis la structure de la molécule. Pour ces substances, on utilise la température d'ébullition normale, la masse moléculaire et le nombre d'atomes dans la molécule pour distinguer entre les isomères. La méthode est applicable à des composés de poids moléculaire élevé, comme la plupart des biomolécules et des molécules larges présentes dans les produits naturels. [source] Limitation of immunoaffinity column for the removal of abundant proteins from plasma in quantitative plasma proteomicsBIOMEDICAL CHROMATOGRAPHY, Issue 5 2009Tomoko Ichibangase Abstract In plasma proteomics, before a proteome analysis, it is essential to prepare protein samples without high-abundance proteins, including albumin, via specific preparation techniques, such as immunoaffinity capture. However, our preliminary experiments suggested that functional changes with use alter the ability of the immunoaffinity column. Thus, in this study, to evaluate the changes of the removal ability of abundant proteins from plasma by the immunoaffinity column, plasma proteome analysis was performed for the long-term test for the reproducibility of the affinity column using the fluorogenic derivatization,liquid chromatography,tandem mass spectrometry method combined with an IgY column. The specific adsorption for albumin decreased with an increase in the number of the column usage before its expiration date. Moreover, it was demonstrated that hydrophobic high molecular weight compounds in plasma adsorbed onto the column materials surface contributed to the functional changes from specific immunoaffinity adsorption into hydrophobic interaction. These results suggested that, in quantitative plasma proteomics studies, it is important to keep in mind the risk of not only the nonselective loss but also the changes in the adsorption ability of the immunoafinity column. Copyright © 2008 John Wiley & Sons, Ltd. [source] | |||||||||||||