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Wilhelm Boland

Publications and source records attributed to Wilhelm Boland.

43 records · Page 3Linked to original sources
PubMed2002

Metal-mediated reactions modeled after nature.

The Collaborative Research Center (CRC) 436 'Metal-Mediated Reactions Modeled after Nature' was founded for the express purpose of analyzing the catalytic principles of metallo-enzymes in order to construct efficient catalysts on a chemical basis. The structure of the active center and neighboring chemical environment in enzymes serves as a focal point for developing reactivity models for the chemical redesign of catalysts. Instead of simply copying enzyme construction, we strive to achieve new chemical intuition based on the results of long-lasting natural evolution. We hope for success, since nature uses a limited set of building blocks, whereas we can apply the full repertoire of chemistry. Key substrates in this approach are small molecules, such as CO2, O2 NO3- and N2. Nature complexes these substrates, activates them and performs chemical transformations--all within the active center of a metalloenzyme. In this article, we report on some aspects and first results of the Collaborative Research Center (CRC) 436, such as nitrate reductase, sphingolipid desaturase, carbonic anhydrase, leucine aminopeptidase and dopamine beta-monooxygenase.

Animals↗
PubMed2002

(R)-(+)-palasonin, a cantharidin-related plant toxin, also occurs in insect hemolymph and tissues.

Gas chromatographic and mass spectroscopic analyses of extracts of cantharidin-containing meloid, clerid, and staphylinid beetles revealed the presence of minor to significant amounts of palasonin, previously only known from seeds and fruits of the Indian shrub Buteafrondosa (Leguminaceae). Unlike (S)-(-)-palasonin (> 99% ee) from B. frondosa, the insects produce palasonin of low ee with the (R)-(+)-enantiomer (0-50% ee) prevailing. The ee of palasonin from individual specimens of predatory insects (Trichodes apiarius), which acquire their chemical protection from cantharidin-producing insects, may vary considerably. The absolute configuration of (S)-(-)-palasonin, previously deduced from indirect chemical and spectroscopic methods, was confirmed by X-ray crystal structure analysis of a cyclic imide derived from (S)-(-)-palasonin and (S)-(-)- 1 -(4-nitrophenyl)-ethylamine.

Animals↗
PubMed2002

The oxylipin chemistry of attraction and defense in brown algae and diatoms.

This review covers the research on brown algal pheromones from the first structural characterisation of an active principle in 1971 to the recent detailed insight into their biosynthesis. Development of analytical methods and bioassays that lead to the identification of a structural variety of different fatty acid-derived pheromones are reported. Special emphasis is focused on the inactivation of initially released pheromones through pericyclic reactions. The impact of pheromone-research on the defensive chemistry of brown algae and diatoms is discussed. 121 references are cited.

Catalysis↗
PubMed2002

Herbivore-induced volatiles induce the emission of ethylene in neighboring lima bean plants.

Herbivore attacks induce leaves to emit a specific blend of volatiles. Here we show that exposure to Tetranychus urticae-induced volatiles, as well as T. urticae infestation and artificial wounding, activates the transcription of the genes involved in the biosynthesis of ethylene [S-adenosylmethionine (SAM) synthetase and 1-aminocyclopropane-1-carboxylic acid oxidase] and a gene involved in the biosynthesis of polyamines from SAM (SAM decarboxylase) in lima bean leaves. Moreover, exposure of leaves to any one of the seven major chemical components of T. urticae-induced volatiles also induces expression of these genes. Furthermore, we found that, when lima bean plants were exposed to T. urticae-induced volatiles, they emitted ethylene. Lima bean plants infested by T. urticae and artificially wounded plants also emitted ethylene. Endogenous polyamine levels were not increased in the exposed leaves or the infested leaves, suggesting that polyamine production from SAM was only slightly promoted at the metabolic levels present in the leaves. We found that jasmonate (JA) accumulated in leaves exposed to T. urticae-induced volatiles, and that both JA and salicylate (SA) accumulated in leaves infested by T. urticae. These findings, as well as results of pharmacological analyses, suggest that, in leaves exposed to T. urticae-induced volatiles, ethylene biosynthesis might be regulated by pathways involving JA and the ethylene positive feedback loop. They also suggest that ethylene biosynthesis might be regulated by signaling pathways involving JA, SA and ethylene in T. urticae-infested leaves.

Adenosylmethionine Decarboxylase↗
PubMed2002

Cloning and functional characterisation of an enzyme involved in the elongation of Delta6-polyunsaturated fatty acids from the moss Physcomitrella patens.

The moss Physcomitrella patens contains high proportions of polyunsaturated very-long-chain fatty acids with up to 20 carbon atoms. Starting from preformed C18 polyunsaturated fatty acids, their biosynthesis involves a sequence of Delta6-desaturation, Delta6-elongation and Delta5-desaturation. In this report we describe for the first time the characterisation of a cDNA (PSE1) of plant origin with homology to the ELO-genes from Saccharomyces cerevisiae, encoding a component of the Delta6-elongase. Functional expression of PSE1 in S. cerevisiae led to the elongation of exogenously supplied Delta6-polyunsaturated fatty acids. By feeding experiments with different trienoic fatty acids of natural and synthetic origin, both substrate specificity and substrate selectivity of the enzyme were investigated. The activity of Pse1, when expressed in yeast, was not sensitive to the antibiotic cerulenin, which is an effective inhibitor of fatty acid synthesis and elongation. Furthermore, the PSE1 gene was disrupted in the moss by homologous recombination. This led to a complete loss of all C20 polyunsaturated fatty acids providing additional evidence for the function of the cDNA as coding for a component of the Delta6-elongase. The elimination of the elongase was not accompanied by a visible alteration in the phenotype, indicating that C20-PUFAs are not essential for viability of the moss under phytotron conditions.

Amino Acid Sequence↗
PubMedDate not supplied

6-Substituted indanoyl isoleucine conjugate induces tobacco plant responses in secondary metabolites.

To characterize the role of the phytotoxin mimic 6-substituted indanoyl isoleucine conjugate 1 in plant secondary metabolism, tobacco (Nicotiana tabacum L. K326) was treated with compound 1. The volatile compounds of tobacco leaves were analyzed by GC-MS. In contrast to the control, three compounds, farnesene (2), santalol (3) and tetradecanal (4), were induced by treatment with 1 mM of compound 1. Concurrently other volatile compounds were also regulated.

Aldehydes↗