Robert D. Minard

Comparison of two thermochemolytic methods for the analysis of lignin in decomposing gymnosperm wood: the CuO oxidation method and the method of thermochemolysis with tetramethylammonium hydroxide (TMAH)

Abstract Comparison of the new TMAH thermochemolysis procedure with the traditional CuO oxidation procedure for lignin characterization in gymnosperm wood and soil formed from degraded gymnosperm wood indicates that an excellent agreement exists between the two methods, especially with regard to the yield of lignin monomers. Moreover, the TMAH procedure appears to be more sensitive for calculation of benzenecarboxylic acid/benzaldehyde ( Ad Al ) ratios, displaying a larger dynamic range than that observed by CuO oxidation. If one considers the simplicity with which the TMAH procedure is carried out, this technique is much more suited to routine analyses of large numbers of samples.

Biological and chemical interactions of pesticides with soil organic matter

There is little doubt that organic matter plays a major role in the binding of pesticides in soil, and that this phenomenon is usually the most important cause for interaction of pesticides in the soil environment. Fulvic or humic acids are the chemicals most commonly involved in the binding interactions. Binding can occur with the original pesticide or a transformation product, the reaction being caused by abiotic agents or biotic agents (microbial or plant enzymes). The reactions or processes involved appear to be the same as those responsible for the formation of humic substances, i.e. for the humification process. Binding of pesticides to organic matter can occur by sorption (Van der Waals forces, hydrogen bonding, hydrophobic bonding), electrostatic interactions (charge transfer, ion exchange or ligand exchange), covalent bonding or combinations of these reactions. Our investigation focused primarily on the binding of substituted phenols and aromatic amines to humus monomers and humic substances. In model reactions, we demonstrated the formation of covalent linkages between pesticides and humus constituents and fulvic or humic acids in the presence of phenol oxidases or clay minerals. With chlorinated phenols and carboxylic acids, it was possible to isolate and identify cross-coupling products and to elucidate the site and type of binding. The binding of chlorinated phenols to humic substances was determined by using 14C-labelled chemicals and by measuring the uptake of radioactivity by the humic material. These experiments provide a base for explaining the formation of bound residues in certain cases and for assuming the toxic potential of the immobilized pollutants.

Structural characterization of bio- and geo-macromolecules by off-line thermochemolysis with tetramethylammonium hydroxide

A new analytical procedure, tetramethylammonium hydroxide thermochemolysis, was used to structurally characterize a variety of bio-and geo-polymers. The technique cleaves esters and some ethers in macromolecular organic matter, yielding low-molecular-mass monomers such as methyl esters of carboxylic acids and methyl ethers of alcohols that are amenable to gas chromatographic analysis. This procedure can be conducted in sealed glass ampoules, which means that it can be easily implemented in any laboratory having gas chromatographic capabilities, in contrast to other chemolytic or pyrolytic procedures. A set of biogeomacromolecules, ranging from gymnosperm and angiosperm woods, natural polyesters such as cutin, dissolved organic matter in natural and oceanic waters, and humic substances were characterized with this procedure. The information obtained provides molecular-level details which can be used to infer structural composition.

Off-line thermochemolysis versus flash pyrolysis for the in situ methylation of lignin: Is pyrolysis necessary?

Abstract Lignin, a major biopolymer in vascular plants, is shown to undergo thermochemolysis reactions when subjected to flash pyrolysis with in situ methylation using tetramethylammonium hydroxide. The product distribution, composed of methylated lignin monomers, implies that the thermochemolysis involves cleavage of the β-O-4 ether bonds in the lignin. Because thermochemolysis occurs with equal effectiveness at sub-pyrolysis temperatures of 300 °C, we conclude that the analytical method does not require use of specialized pyrolysis equipment, and can be implemented in a batch mode in which internal standards can be added and the products quantified.

Cross-linkage between anilines and phenolic humus constituents

W The pesticide degradation intermediates 4-chloroaniline, 3,4-dichloroaniline, and 2,6-diethylaniline were examined for their ability to react with various phenolic humus constituents in the presence of a fungal phenol oxidase. An initial indication of a cross-coupling reaction was obtained by color formation. Although anilines alone were not transformed by a phenol oxidase isolated from the fungus Rhizoctonia praticola, they readily cross-linked with phenolic acids or their enzymatic products to form hybrids in the presence of the enzyme. A number of hybrid dimers, trimers, and tetramers were isolated and determined by mass spectrometric analysis. The identities of three hybrid dimers formed from syringic acid coupled with 4-chloroaniline, 3,4-dichloroaniline, or 2,g-diethylaniline and a hybrid tetramer from protocatechuic acid coupled with 2,6-diethylaniline were determined. The formation of the hybrid dimer N-(2,6-diethylphenyl)-2,6dimethoxy-p-benzoquinone imine from a cross-linkage between syringic acid and 2,6-diethylaniline was quantitatively evaluated.

Hydrogen cyanide polymers, comets and the origin of life

Hydrogen cyanide polymers--heterogeneous solids ranging in colour from yellow to orange to brown to black--could be major components of the dark matter observed on many bodies of the outer solar system including asteroids, moons, planets and, especially, comets. The presence on cometary nuclei of frozen volatiles such as methane, ammonia and water subjected to high energy sources makes them attractive sites for the ready formation and condensed-phase polymerization of hydrogen cyanide. This could account for the dark crust observed on Comet Halley in 1986 by the Vega and Giotto missions. Dust emanating from its nucleus would arise partly from HCN polymers as suggested by the Giotto detection of free hydrogen cyanide, CN radicals, solid particles consisting only of H, C and N, or only of H, C, N, O, and nitrogen-containing organic compounds. Further evidence for cometary HCN polymers could be expected from in situ analysis of the ejected material from Comet Tempel 1 after collision with the impactor probe from the two-stage Deep Impact mission on July 4, 2005. Even more revealing will be actual samples of dust collected from the coma of Comet Wild 2 by the Stardust mission, due to return to Earth in January 2006 for analyses which we have predicted will detect these polymers and related compounds. In situ results have already shown that nitriles and polymers of hydrogen cyanide are probable components of the cometary dust that struck the Cometary and Interstellar Dust Analyzer of the Stardust spacecraft as it approached Comet Wild 2 on January 2, 2004. Preliminary evidence (January 2005) obtained by the Huygens probe of the ongoing Cassini-Huygens mission to Saturn and its satellites indicates the presence of nitrogen-containing organic compounds in the refractory organic cores of the aerosols that give rise to the orange haze high in the atmosphere of Titan, Saturns largest moon. Our continuing investigations suggest that HCN polymers are basically of two types: ladder structures with conjugated -C=N- bonds and polyamidines readily converted by water to polypeptides. Thermochemolysis GC-MS studies show that cleavage products of the polymer include alpha-amino acids, nitrogen heterocycles such as purines and pyrimidines, and provide evidence for peptide linkages. Hydrogen cyanide polymers are a plausible link between cosmochemistry and the origin of informational macromolecules. Implications for prebiotic chemistry are profound. Following persistent bolide bombardment, primitive Earth may have been covered by water and carbonaceous compounds, particularly HCN polymers which would have supplied essential components for establishing protein/nucleic acid life.

Enzyme-mediated coupling of 3,4-dichloroaniline and ferulic acid: a model for pollutant binding to humic materials.

To investigate the incorporation of chloroanilines into humic substances, the reaction of ferulic acid with three different chloroanilines in the presence of a laccase of the fungus Rhizoctonia praticola was investigated. Under the reaction conditions used, chloroanilines alone were not transformed by the laccase, but in the presence of ferulic acid they formed cross-coupling products. The reactivity of anilines decreased with increasing chlorine substitution on the ring. Two dimeric compounds were isolated from the reaction assay of ferulic acid alone. The dimers were found to have phenylcoumaran and lactone structures

Comment on the origin of benzenecarboxylic acids in pyrolysis methylation studies

The presence of benzenecarboxylic acid methyl esters in thermochemolysis or pyrolysis products of humic acids, produced in the presence of tetramethylammonium hydroxide (TMAH), has recently been attributed to the existence of benzenecarboxylic acid moieties in the original materials being examined by this new technique for structural elucidation. Our studies of wood and model compounds, materials free of carboxylic acid-containing structures, by this method indicate that certain benzenecarboxylic acids are produced by the TMAH reagent in the course of reaction at elevated temperatures. This indicates that one should exercise due caution in interpreting the presence of these benzenecarboxylic acid methyl esters as pre-existing structural humic acids.

Identification of protein remnants in insoluble geopolymers using TMAH thermochemolysis/GC-MS

Abstract Thermochemolysis with tetramethylammonium hydroxide (TMAH) was utilized to analyze peptide-like material in insoluble residues of geochemical samples. Product identification was performed by gas chromatography/mass spectrometry using bovine albumin and di-, tri- and oligo-peptides. Most of the identified amino acid derivatives originate from the cleavage of the peptide bonds and subsequent methylation of the carboxylic and the amino groups. Some products are explained by deamination of aromatic amino acids. Only two products were identified that experienced chemical rearrangement after methylation. TMAH/thermochemolysis of algal material resulted in products comparable to those obtained from albumin. Amino acid derivatives were also identified among the TMAH/thermochemolysis products of refractory biopolymer of the alga Scenedesmus communis and the HCl-hydrolysis residue of the humin from an algal sapropel. These results strongly indicate that for those samples, hydrolysis fails to extract all proteinaceous and peptide-like components, possibly because these approaches rely on extraction of peptides and amino acids into solution and some of these are entrapped within a non-extractable hydrophobic network. However, alternative explanations for this behavior are possible. For example, at the higher temperatures and pressures and strongly basic conditions used in TMAH themochemolysis, penetration of this hydrophobic barrier takes place thus allowing breakdown and methylation of protein remnants.

Shared genes related to aggression, rather than chemical communication, are associated with reproductive dominance in paper wasps (Polistes metricus)

BackgroundIn social groups, dominant individuals may socially inhibit reproduction of subordinates using aggressive interactions or, in the case of highly eusocial insects, pheromonal communication. It has been hypothesized these two modes of reproductive inhibition utilize conserved pathways. Here, we use a comparative framework to investigate the chemical and genomic underpinnings of reproductive dominance in the primitively eusocial wasp Polistes metricus. Our goals were to first characterize transcriptomic and chemical correlates of reproductive dominance and second, to test whether dominance-associated mechanisms in paper wasps overlapped with aggression or pheromone-related gene expression patterns in other species. To explore whether conserved molecular pathways relate to dominance, we compared wasp transcriptomic data to previous studies of gene expression associated with pheromonal communication and queen-worker differences in honey bees, and aggressive behavior in bees, Drosophila, and mice.ResultsBy examining dominant and subordinate females from queen and worker castes in early and late season colonies, we found that cuticular hydrocarbon profiles and genome-wide patterns of brain gene expression were primarily associated with season/social environment rather than dominance status. In contrast, gene expression patterns in the ovaries were associated primarily with caste and ovary activation. Comparative analyses suggest genes identified as differentially expressed in wasp brains are not related to queen pheromonal communication or caste in bees, but were significantly more likely to be associated with aggression in other insects (bees, flies), and even a mammal (mice).ConclusionsThis study provides the first comprehensive chemical and molecular analysis of reproductive dominance in paper wasps. We found little evidence for a chemical basis for reproductive dominance in P. metricus, and our transcriptomic analyses suggest that different pathways regulate dominance in paper wasps and pheromone response in bees. Furthermore, there was a substantial impact of season/social environment on gene expression patterns, indicating the important role of external cues in shaping the molecular processes regulating behavior. Interestingly, genes associated with dominance in wasps were also associated with aggressive behavior in bees, solitary insects and mammals. Thus, genes involved in social regulation of reproduction in Polistes may have conserved functions associated with aggression in insects and other taxa.