Binding interactions between suberin monomer components and pesticides.

Understanding the role of biomacromolecules and their interactions with pollutants is a key for elucidating the sorption mechanisms and making an accurate assessment of the environmental fate of pollutants. The knowledge of the sorption properties of the different constituents of these biomacromolecules may furnish a significant contribution to this purpose. Suberin is a very abundant biopolymer in higher plants. In this study, suberin monomers isolated from cork were analyzed by thermally-assisted methylation with tetramethylammonium hydroxide (TMAH) in a pyrolysis unit coupled to gas chromatography-mass spectrometry (GC/MS). The isolated monomer mixture was used to study the sorption of three pesticides (isoproturon, methomyl and oxamyl). The modes of pesticide-sorbent interactions were analyzed by means of two modeling calculations, the first one representing only the mixture of suberin monomers used in the sorption study, and the second one including glycerol to the mixture of suberin monomers, as a building block of the suberin molecule. The results indicated that the highest sorption capacity exhibited by the sorbent was for isoproturon (33%) being methomyl and oxamyl sorbed by the main suberin components to a lesser extent (3% and<1%, respectively). In addition to van der Waals interactions with the apolar region of sorbent and isoproturon, modeling calculations evidenced the formation of a hydrogen bond between the isoproturon NH group and a carboxylic oxygen atom of a suberin monomer. In the case of methomyl and oxamyl only weak van der Waals interactions stabilize the pesticide-sorbent adducts. The presence of glycerol in the model provoked significant changes in the interactions with isoproturon and methomyl.

Characterisation and discrimination of various types of lac resin using gas chromatography mass spectrometry techniques with quaternary ammonium reagents.

A variety of lac resin samples obtained from artists' suppliers, industrial manufacturers, and museum collections were analysed using gas chromatography mass spectrometry (GCMS) and reactive pyrolysis GCMS with quaternary ammonium reagents. These techniques allowed a detailed chemical characterisation of microgram-sized samples, based on the detection and identification of derivatives of the hydroxy aliphatic and cyclic (sesquiterpene) acids that compose the resin. Differences in composition could be related to the nature of the resin, e.g. wax-containing (unrefined), bleached, or aged samples. Furthermore, differences in the relative abundances of aliphatic hydroxyacids appear to be associated with the biological source of the resin. The diagnostic value of newly characterised lac components, including 8-hydroxyacids, is discussed here for the first time. Identification of derivatised components was aided by AMDIS deconvolution software, and discrimination of samples was enhanced by statistical evaluation of data using principal component analysis. The robustness of the analyses, together with the minimal sample size required, make these very powerful approaches for the characterisation of lac resin in museum objects. The value of such analyses for enhancing the understanding of museum collections is illustrated by two case studies of objects in the collection of the Philadelphia Museum of Art: a restorer's varnish on a painting by Luca Signorelli, and a pictorial inlay in an early nineteenth-century High Chest by George Dyer.

Main lipophilic extractives in different paper pulp types can be removed using the laccase-mediator system.

Lipophilic extractives in wood and other lignocellulosic materials exert a negative impact in pulp and paper manufacturing causing the so-called pitch problems. In this work, the appropriateness of an enzymatic treatment using the laccase-mediator system for pitch biocontrol is evaluated. With this purpose, three pulp types representative for different raw materials and pulping processes-eucalypt kraft pulping, spruce thermomechanical pulping, and flax soda-anthraquinone pulping-were treated with a high-redox-potential laccase from the basidiomycete Pycnoporus cinnabarinus in the presence of 1-hydroxybenzotriazole as a redox mediator. The gas chromatography and gas chromatography/mass spectrometry analyses of the lipophilic extractives from the enzymatically treated pulps revealed that the laccase-mediator treatment completely or greatly removed most of the pitch-causing lipophilic compounds present in the different pulps including: (1) free and conjugated sitosterol in eucalypt paper pulp; (2) resin acids, sterol esters, and triglycerides in spruce pulp; and (3) sterols and fatty alcohols in the flax pulp. Different amounts of free and conjugated 7-oxosterols were found as intermediate products in the oxidation of pulp sterols. Therefore, the laccase-mediator treatment is reported as an efficient method for removing pitch-causing lipophilic compounds from paper pulps obtained from hardwood, softwood, and nonwoody plants.

Gas chromatography/mass spectrometry demonstration of steryl glycosides in eucalypt wood, Kraft pulp and process liquids.

The occurrence of steryl glycosides (SG) and acyl steryl glycosides (ASG) in eucalypt (Eucalyptus globulus) wood has been investigated. These compounds were analyzed as their trimethylsilyl ethers by gas chromatography/mass spectrometry (GC/MS) using a 15 m length high-temperature capillary column with a thin film, and identified on basis of their mass spectra and relative retention times comparing with those of authentic standards. Significant amounts of SG were identified in eucalypt wood whilst only traces of ASG could be detected. Eucalypt SG and ASG occur in the pyranoside form, which is readily distinguishable from the furanoside configuration by the mass spectra of their trimethylsilyl derivatives. The sterol part of the SG and ASG consisted of sitosterol, being sitosteryl 3beta-D-glucopyranoside and sitosteryl (6'-O-palmitoyl)-3beta-D-glucopyranoside, the major SG and ASG found in E. globulus wood. The presence of SG and ASG was also investigated after kraft cooking by analyzing unbleached pulp and process water samples. The GC/MS results also revealed the presence of sitosteryl 3beta-D-glucopyranoside in these samples. By contrast, no ASG could be detected. Therefore, we have shown that SG survive the kraft cooking and can be found at least partly intact after pulping, being a possible cause for pitch deposits together with free and esterified sterols.

Prevalence between different alpha subunits performing the benzodiazepine binding sites in native heterologous GABA(A) receptors containing the alpha2 subunit.

The presence of two heterologous alpha subunits and a single benzodiazepine binding site in the GABA(A) receptor implicates the existence of pharmacologically active and inactive alpha subunits. This fact raises the question of whether a particular alpha subtype could predominate performing the benzodiazepine binding site. The hippocampal formation expresses high levels of alpha subunits with different benzodiazepine binding properties (alpha1, alpha2 and alpha5). Thus, we first demonstrated the existence of alpha2-alpha1 (36.3 +/- 5.2% of the alpha2 population) and alpha2-alpha5 (20.2 +/- 2.1%) heterologous receptors. A similar alpha2-alpha1 association was observed in cortex. This association allows the direct comparison of the pharmacological properties of heterologous native GABA(A) receptors containing a common (alpha2) and a different (alpha1 or alpha5) alpha subunit. The alpha2 subunit pharmacologically prevailed over the alpha1 subunit in both cortex and hippocampus (there was an absence of high-affinity binding sites for Cl218,872, zolpidem and [3H]zolpidem). This prevalence was directly probed by zolpidem displacement experiments in alpha2-alpha1 double immunopurified receptors (K(i) = 295 +/- 56 nM and 200 +/- 8 nM in hippocampus and cortex, respectively). On the contrary, the alpha5 subunit pharmacologically prevailed over the alpha2 subunit (low- and high-affinity binding sites for zolpidem and [3H]L-655,708, respectively). This prevalence was probed in alpha2-alpha5 double immunopurified receptors. Zolpidem displayed a single low-affinity binding site (K(i) = 1.73 +/- 0.54 microM). These results demonstrated the existence of a differential dominance between the different alpha subunits performing the benzodiazepine binding sites in the native GABA(A) receptors.

Lipophilic extractives in process waters during manufacturing of totally chlorine free kraft pulp from eucalypt wood.

The chemical composition of lipophilic extractives from process waters throughout a totally chlorine free (TCF) bleaching sequence after kraft pulping of eucalypt wood has been studied. These compounds are among the most problematic wood constituents for both TCF and zero liquid effluent (ZLE) processes, since they tend to accumulate in circuits resulting in the formation of the so-called pitch deposits causing serious problems in the pulp and paper industry. Pitch deposits collected at different parts of the pulp mill were also characterized and their composition compared with that of lipophilic compounds in process waters and Eucalyptus globulus wood. The identification of these compounds from process waters, wood and pitch deposits was performed by gas chromatography and gas chromatography-mass spectrometry using short- and medium-length high temperature capillary columns. Sterols, sterol esters, steroid ketones and steroid hydrocarbons were the main compounds identified. These chemical species arise from eucalypt wood extractives that survive the pulping and are released from pulp into the process waters during the bleaching process. Finally, they can deposit in pulp and on different parts of the mill or remain suspended in process waters being discharged in effluents.

The biotechnological control of pitch in paper pulp manufacturing.

At present, microbial and enzymatic preparations for the control of triglyceride-containing pitch deposits during the manufacture of mechanical and sulfite paper is commercially available. However, biotechnological products for pitch control in other pulping processes, such as alkaline pulping, are under development. These products include new fungi for the removal of steroids involved in pitch deposit formation in chlorine-free pulps, to be used as a biological pretreatment of wood before pulping. Simultaneously, tailor-made enzymes are being produced using protein-engineering techniques, enabling the specific removal of pitch contaminant compounds from paper pulp.

Time course of fungal removal of lipophilic extractives from Eucalyptus globulus wood.

Free and esterified sitosterol, the main lipophilic constituents of eucalypt wood extractives, have been associated with the formation of pitch deposits during manufacturing of environmentally-sound paper pulp from Eucalyptus globulus wood. These, and other lipophilic compounds, were analyzed by gas chromatography-mass spectrometry in the course of wood treatments (up to 7 weeks) with four extractive-degrading fungi in order to optimize biotechnological control of pitch deposition in eucalypt pulp (with moderate loss of wood weight). In contrast to commercialized fungi used in pitch control, which are not able to degrade sitosterol, the fungi investigated in this paper produced a rapid decline of both free and esterified sterols in wood. The degradation rate of steroid hydrocarbons and squalene was moderate, and the amount of steroid ketones (probably formed during oxidative degradation of steroids) and triglycerides increased at different stages of wood treatment. Up to 95% removal of total steroids (including free and esterified sterols, steroid ketones and steroid hydrocarbons) by fungi was obtained at the end of wood treatment under the solid-state fermentation conditions used. The most promising results from the point of view of industrial applicability, however, were obtained after 1-2 weeks of treatment with either Phlebia radiata or Poria subvermispora, which enabled 70% steroid removal with a moderate wood weight loss of 1-4%.

Supercritical carbon dioxide extraction of lipids from Eucalyptus globulus wood.

Various typical lipid components of wood extractives have been isolated from Eucalyptus globulus wood by supercritical carbon dioxide modified with methanol. The influence of various extraction parameters on the yield and qualitative composition of the extracts have been studied. The extracts were analyzed by gas chromatography-mass spectrometry and compared with those obtained by Soxhlet extraction with acetone, the standard method for the determination of wood extractives. The qualitative and quantitative results obtained by both methods were in good agreement. The experimental planning to asses the influence of pressure, temperature and percentage of methanol and their interactions on the extraction efficiency was carried out with a factorial design, followed by multiple linear regression algorithm.

Analysis of pitch deposits produced in kraft pulp mills using a totally chlorine free bleaching sequence.

Two organic deposits accumulated in a Kraft pulp mill during pulping of Eucalyptus globulus wood and throughout a TCF (totally chlorine free) bleaching sequence were characterized. One deposit was collected after cooking and an oxygen delignification stage while the other was collected after bleaching with hydrogen peroxide. The deposits were Soxhlet extracted with acetone, and the extracts redissolved in chloroform and subsequently analyzed by gas chromatography (GC) and GC-mass spectrometry (MS) using short and medium length high temperature capillary columns, respectively. On the other hand, the insoluble residues left after the acetone extraction were analyzed by Curie-point flash pyrolysis-GC-MS and by pyrolysis-methylation-GC-MS. The compounds identified in the deposits arise from the E. globulus wood lipophilic extractives that survive the pulping and bleaching processes. Triglycerides were completely hydrolyzed during the Kraft cooking and the fatty acids dissolved. Steroids (alcohols, hydrocarbons, ketones and esters) and waxes were the main components in the deposit collected after the oxygen delignification stage. After the bleaching with hydrogen peroxide, content of the waxes were reduced and fatty acids appeared. High amounts of fatty acids salts were also identified in the deposit collected after the oxygen stage, and in minor amounts in the deposit collected after hydrogen peroxide bleaching. In contrast, this deposit was mainly made up of high amounts of lignin-derived phenolic moieties.