PAH metabolism in the earthworm Eisenia fetida – identification of phase II metabolites of phenanthrene and pyrene

Polycyclic aromatic hydrocarbons (PAHs) are soil contaminants. Because of their high lipophilicity, PAHs are associated with the organic matter in the soil. Transformation of PAHs generates polar metabolites and the interaction with organic matter in the soil changes. The polar PAH metabolites are persistent, highly water-soluble and potentially leachable from the soil; the understanding of transformation of PAHs to polar metabolites in the responsible organisms is of great importance. Here, we present a study of transformation of the PAHs pyrene and phenanthrene, by the common earthworm Eisenia fetida. The study showed that E. fetida in hydroponic culture was able to transform PAHs to conjugated phase II metabolites. We detected phenanthrene and pyrene metabolites with single- and multiple-phase II-conjugated groups. Sulphate conjugates were excreted to experiment water, and glucuronide and glucoside conjugates and metabolites with several hydroxylations and multiple conjugations were detected in worm tissue. The results demonstrate that earthworms are able to transform PAHs to water-soluble phase II metabolites, which can be excreted to the surrounding environment.     

Loop Groups and Twin Buildings

In these notes we describe some buildings related to complex Kac–Moody groups. First we describe the spherical building of SL_n() (i.e. the projective geometry PG(ⁿ)) and its Veronese representation. Next we recall the construction of the affine building associated to a discrete valuation on the rational function field (z). Then we describe the same building in terms of complex Laurent polynomials, and introduce the Veronese representation, which is an equivariant embedding of the building into an affine Kac–Moody algebra. Next, we introduce topological twin buildings. These buildings can be used for a proof which is a variant of the proof by Quillen and Mitchell, of Bott periodicity which uses only topological geometry. At the end we indicate very briefly that the whole process works also for affine real almost split Kac–Moody groups.Supported by a Heisenberg fellowship by the Deutsche Forschungsgemeinschaft.     

A microcomputer-controlled titrator for automated individual analysis

A titration unit for automatic analysis systems is described. The titrator performs different titrations specified by strings of digital parameters. It has 4 independent titration stations with individual electrode systems. A multiburette with 20 cylinders provides all stations with the necessary reagents. End-point titrations, and incremental and equilibrium titrations are controlled by a microcomputer. In combination with a sample transport and a desk calculator, the titrator can be used to process automatically samples of different natures which require different treatment.     

An elastic network model to identify characteristic stress response genes

Exposing eukaryotic cells to a toxic compound and subsequent gene expression profiling may allow the prediction of selected toxic effects based on changes in gene expression. This objective is complicated by the observation that compounds with different modes of toxicity cause similar changes in gene expression and that a global stress response affects many genes. We developed an elastic network model of global stress response with nodes representing genes which are connected by edges of graded coexpression. The expression of only few genes have to be known to model the global stress response of all but a few atypical responder genes. Those required genes and the atypical response genes are shown to be good biomarker for tox predictions. In total, 138 experiments and 13 different compounds were used to train models for different toxicity classes. The deduced biomarkers were shown to be biologically plausible. A neural network was trained to predict the toxic effects of compounds from profiling experiments. On a validation data set of 189 experiments with 16 different compounds the accuracy of the predictions was assessed: 14 out of 16 compounds have been classified correctly. Derivation of model based biomarkers through the elastic network approach can naturally be extended to other areas beyond toxicology since subtle signals against a broad response background are common in biological studies.     

Luminescence Enhancement from Silica-Coated Gold Nanoparticle Agglomerates Following Multi-photon Excitation

Multi-photon absorption induced luminescence (MAIL) from bare gold nanoparticles, silica-coated particles, as well as silica-coated agglomerated gold nanoparticles suspended in aqueous solution was studied by using time-resolved and steady-state luminescence spectroscopy. The nanoparticles were excited by femtosecond pulses of wavelengths ranging from 630 nm to 900 nm. The luminescence from the particles exhibits a broad spectrum in the UV and VIS region. The time-resolved measurements indicate a luminescence lifetime of a few ps, limited by the response of the experimental system. The studied dependence of the MAIL efficiency on the excitation wavelength showed that the luminescence from silica-coated agglomerates was enhanced over the whole range of excitation wavelengths, when compared to the luminescence from individual gold nanoparticles. The agglomerates show an almost excitation wavelength independent efficiency of the MAIL, while for individual nanoparticles a rapid decrease of the MAIL efficiency was observed with increasing excitation wavelength. The observed enhancement of the MAIL from the agglomerated nanostructures can be attributed to the presence of localized surface plasmon resonances in the spectral region corresponding to the excitation wavelengths. The high MAIL efficiency from the agglomerated nanoparticle structures in the near-infrared could be an advantage in the expanding field of luminescence-based-imaging, as well as in biosensor technology.     

Coarse equivalences of Euclidean buildings

We prove the following rigidity results. Coarse equivalences between metrically complete Euclidean buildings preserve spherical buildings at infinity. If all irreducible factors have dimension at least two, then coarsely equivalent Euclidean buildings are isometric (up to scaling factors); if in addition none of the irreducible factors is a Euclidean cone, then the isometry is unique and has finite distance from the coarse equivalence.     

Differentiability of continuous homomorphisms between smooth loops

It is a well-known fact that a continuous homomorphism between Lie groups is analytic. We prove a similar result (Thm. 1.8) for continuous homomorphisms of differentiable left or right loops in section 1 of this paper. Section 2 deals with images and kernels of such homomorphisms. Again, the results obtained are quite analogous to the Lie group case. The paper ends with applications of Theorem 1.8. For example, it turns out that the group of continuous automorphisms of a smooth generalized polygon is a Lie transformation group with respect to the compact-open topology.     

TBADH activity in water-miscible organic solvents: correlations between enzyme performance, enantioselectivity and protein structure through spectroscopic studies

The enantioselective reduction of 2-pentanone to (R)- and (S)-2-pentanol by Thermoanaerobacter (formerly Thermoanaerobium) brockii alcohol dehydrogenase (TBADH) in mixtures of water and water-miscible organic solvents was investigated. Significant enzymatic activity was retained in up to 87% methanol, ethanol and acetonitrile. The changes in enzyme activity as a function of organic solvent were correlated to structural alterations of TBADH with a series of spectroscopic studies (fluorescence, fluorescence quenching and circular dichroism (CD)). Interestingly, this study shows that the tetrameric form of TBADH is not critical for catalytic performance.