Environmental chemistry of PCB-replacement compounds - VI - composition and metabolism of Wemcol ®, an isopropylbiphenyl formulation

Wemcol is a technical isopropylbiphenyl formulation that is used as a substitute for polychlorobiphenyl. According to the producer Wemcol is 4-isopropylbiphenyl, but we found our sample to consist of 60.3% 3-isopropylbiphenyl, 38.6% 4-isopropylbiphenyl and 3,5-, 3,3′-, 3,4′- and 4,4′-diisopropylbiphenyl in amounts of 0.3%, 0.4%, 0.2% and 0.1% respectively. The two major components of the mixture are metabolized in the rat by two routes : oxidation of the isopropyl group and hydroxylation of the aromatic nuclei. Rats fed the technical mixture retained 3- and 4-isopropylbiphenyl in a ratio 4.3 : 1 in their abdominal fat, whilst the ratio in the mixture is 1.6 : 1. One week after the simultaneous feeding of equal amounts of Wemcol, 4,4′-dichlorobiphenyl, 2,4′,5-trichlorobiphenyl and 2,2′,5,5′-tetrachlorobiphenyl, the isopropylbiphenyls, in contrast to the chlorobiphenyls, could no longer be detected in the abdominal fat of rats.     

Die biologische Bedeutung der chemischen Feinstruktur bakterieller Zellgrenzflächen

The Science of Nature -     

Ozone Deposition at a Forest Site in NE Bavaria

The dry deposition of ozone to aconiferous forest in northeastern Bavaria(southern Germany) was quantified during 1999with both the eddy correlation method and a bigleaf model. The model included parameterizationsof the atmospheric transfer resistances fromdirect measurements, stomatal resistance from aplant ecological model, and an estimation of thecuticle resistance as function of leaf wetness.Early in the season, the measured and themodelled deposition fluxes were in goodagreement, although the modelled fluxes tended tounderestimate the measured ones. Thisunderestimation was more pronounced in the latesummer, when high nocturnal fluxes werefrequently measured. The model parameterizationof the cuticle and the stomatal resistances didnot allow for such high fluxes. In these cases,the 24 hour average of the measured fluxes wereup to 4.5 times higher than the modelled ones.The reasons for these large discrepancies remainunknown. However, assigning the unaccounted partof the deposition to a nonstomatal surfacedeposition pathway, a new parameterization of therespective resistance yielded an average value of300 s m^-1. It exhibited a decreasing trendthrough the vegetation period.     

Biomolecules preserved in ca. 168 million year old fossil conifer wood

Biomarkers are widely known to occur in the fossil record, but the unaltered biomolecules are rarely reported from sediments older than Paleogene. Polar terpenoids, the natural products most resistant to degradation processes, were reported mainly from the Tertiary conifers, and the oldest known are Cretaceous in age. In this paper, we report the occurrence of relatively high concentrations of ferruginol derivatives and other polar diterpenoids, as well as their diagenetic products, in a conifer wood Protopodocarpoxylon from the Middle Jurassic of Poland. Thus, the natural product terpenoids reported in this paper are definitely the oldest polar biomolecules detected in geological samples. The extracted phenolic abietanes like ferruginol and its derivatives (6,7-dehydroferruginol, sugiol, 11,14-dioxopisiferic acid) are produced only by distinct conifer families (Cupressaceae s. l., Podocarpaceae and Araucariaceae), to which Protopodocarpoxylon could belong based on anatomical characteristics. Therefore, the natural product terpenoids are of great advantage in systematics of fossil plant remains older than Paleogene and lacking suitable anatomical preservation.