Characterization of Lead–Phytochelatin Complexes by Nano-Electrospray Ionization Mass Spectrometry

The role of phytochelatins (PCn, metal-binding oligopeptides with the general structure (γGlu-Cys)n-Gly (n = 2–11) in metal detoxification is assumed to be based on immobilization of metals, which prevents binding of metals to important biomolecules. Although induction of phytochelatin synthesis has often been observed in algae upon exposure to metals, direct evidence for binding of the inducing metal to phytochelatins is scarce. In this study, a nano-electrospray ionization mass spectrometry (nano-ESI-MS) method is developed for identification and characterization of Pb(II)–PCn and Zn(II)–PCn complexes. Complexes of Pb(II) with standard PCn (n = 2–4; 0.25 mM Pb(II) and 0.5 mM PCn) were examined by nano-ESI-MS with respect to their stoichiometry. Pb–PCn mass spectra indicated the presence of the [M + H]+ peak of PCn and complexes with various stoichiometries. Analysis of Pb–PC2 allowed the identification of four different complexes observed at m/z 746.10, 952.06, 1285.24, and 1491.20, corresponding to [Pb–PC2]+, [Pb2–PC2]+, [Pb–(PC2)2]+, and [Pb2–(PC2)2]+. Their m/z indicated coordination of Pb(II) by PC2 through the thiol groups of PC cysteine and possibly carboxylic groups. For each of the standard PC3 and PC4, two different complexes were observed, corresponding to Pb–PC3, Pb2–PC3, Pb–PC4, and Pb2–PC4. The measured isotopic patterns were for all complexes identical to the theoretical isotopic patterns. Addition of Zn(II) (0.125–5 mM) to previously formed Pb–PC2 complexes showed the appearance of the [Zn–PC2]+ complexes at m/z 602.05 and the decrease of the [Pb–PC2]+ peak. These findings corroborate the postulated Pb–PC complexes from a previous study using size exclusion chromatography of PC extracted from algae, as well as the concurrent formation of Pb–, Zn–, and Cu–PC complexes in algae

Environmental Fate of Chiral Pollutants – the Necessity of Considering Stereochemistry

Many organic compounds regulated by environmental laws are chiral and are released into the environment as racemates. 3-Phenylbutanoic acid and mecoprop, two chiral pollutants, were enantioselectively degraded by pure cultures of microorganisms. This indicates the importance of assessing the environmental impact of stereoisomers separately, because selective enrichment of one of the enantiomers may occur in the environment. Field studies on the fate of highly polar, chiral compounds, like sulfophenylcarboxylates, are hampered by the lack of appropriate analytical methods for the separation of the enantiomers. Therefore, a method based on capillary electrophoresis with α-cyclodextrin as chiral selector was developed to separate the enantiomers of such compounds. In a field study at a Swiss waste disposal site, the fate of the chiral herbicide mecoprop was investigated. The enantiomeric ratio of (R)-mecoprop to (S)-mecoprop altered during groundwater passage of landfill leachate. This is a strong indication for in situ biodegradation. Our data imply that not only the enantiomers of a chiral drug or pesticide may exert different effects on the biological targets, but also their biodegradation and environmental fate may differ

Determination of Hydrophilic and Amphiphilic Organic Pollutants in the Aquatic Environment

Environmental chemists performing monitoring or process-oriented fate and behavior studies on organic micropollutants face the challenge of having to determine low concentrations of problem compounds in complex mixtures and difficult matrices, such as sewage sludge, surface and groundwater. Selective extraction and enrichment help to overcome sensitivity limitations and also to reduce the number of different species in the sample. A subsequent chromatographic separation step, together with analyte-specific detection, finally allows to identify and quantify single analytes in the presence of other organic material. This article describes a selection of analytical development work carried out at EAWAG for the determination of hydrophilic and amphiphilic organic pollutants in the aquatic environment

Toxicity of emerging antifouling biocides to non-target freshwater organisms from three trophic levels

Antifouling (AF) systems provide the most cost-effective protection against biofouling. Several AF biocides have, however, caused deleterious effects in the environment. Subsequently, new compounds have emerged that claim to be more environment-friendly, but studies on their toxicity and environmental risk are necessary in order to ensure safety. This work aimed to assess the toxicity of three emerging AF'biocides, tralopyril, triphenylborane pyridine (TPBP) and capsaicin, towards non-target freshwater organisms representing three trophic levels: algae (Chlamydomonas reinhardtii), crustacean (Daphnia magna) and fish (Danio rerio). From the three tested biocides, tralopyril had the strongest inhibitory effect on C. reinhardtii growth, effective quantum yield and adenosine triphosphate (ATP) content. TPBP caused sub-lethal effects at high concentrations (100 and 250 mu g L-1), and capsaicin had no significant effects on algae. In the D. magna acute immobilisation test, the most toxic compound was TPBP. However, tralopyril has a short half-life and quickly degrades in water. With exposure solution renewals, tralopyril's toxicity was similar to TPBP. Capsaicin did not cause any effects on daphnids. In the zebrafish embryo toxicity test (zFET) the most toxic compound was tralopyril with a 120 h - LC50 of 5 mu g L-1, TPBP's 120 h - LC50 was 447.5 mu g L-1. Capsaicin did not cause mortality in zebrafish up to 1 mg L-1 . Sub- lethal effects on the proteome o f zebrafish embryos were analysed for tralopyril and TPBP. Both general stress- related and compound-specific protein changes were observed. Five proteins involved in energy metabolism, eye structure and cell differentiation were commonly regulated by both compounds. Tralopyril specifically induced the upregulation of 6 proteins implicated in energy metabolism, cytoskeleton, cell division and mRNA splicing whilst TPBP lead to the upregulation of 3 proteins involved in cytoskeleton, cell growth and protein folding. An ecological risk characterization was performed for a hypothetical freshwater marina. This analysis identified capsaicin as an environment-friendly compound while tralopyril and TPBP seem to pose a risk to freshwater ecosystems. Noneless, more studies on the characterization o f the toxicity, behaviour and fate of these AF biocides in the environment are necessary since this information directly affects the outcome o f the risk assessment

Gonadal Malformations in Whitefish from Lake Thun: Defining the Case and Evaluating the Role of EDCs

The objectives of this project were to evaluate i) whether the gonad alterations of whitefish (Coregonus lavaretus spp.) in Lake Thun represent abnormal morphological variations specific to this lake, and, if so, ii) whether the malformations are related to chemical exposure, in particular to exposure to endocrine-disrupting compounds (EDCs). Large-scale monitoring data revealed that, although whitefish in other lakes display some background variation of gonad morphology, the situation in Lake Thun, is unique because of the significantly higher prevalence of gonad malformations. The abnormal variations of whitefish gonad morphology include aplasias, compartmentations, fusions, and intersex. In the search for the factor(s) causing the gonad malformations, coregonids were exposed from fertilization up to maturity to Lake Thun water and plankton or to contaminants possibly being present in the lake, including trinitrotoluenes, and naphtalene sulfonates. Since these experiments are still ongoing, a conclusive answer cannot be given yet, but initial observations point to a role of the lake plankton. The possible presence of EDCs in Lake Thun was assessed using bioanalytics and biomarkers. The bioanalytical studies found estrogenic activities in concentrated plankton extracts of Lake Thun, however, estrogenic activities occurred also in plankton extracts of reference lakes. Bioassay-directed fractionation of the plankton samples points to degradation products of natural substances as a cause of the estrogenic activity. Examination of Lake Thun whitefish for EDC biomarkers such as vitellogenin, sex steroid levels or intersex frequency yielded no indications of exposure to EDCs, neither in fish with normal nor in fish with abnormal gonad morphology. Long-term laboratory exposure of developing coregonids to the prototype estrogenic compound, 17?-estradiol, resulted in an increased frequency of intersex gonads, but did not induce the other gonad malformations typical for Lake Thun coregonids. In summing up, the currently available evidence does not support an EDC or chemical etiology of the gonad malformations, however, this preliminary conclusion needs to be substantiated in the ongoing investigations. The project also highlights the need for more detailed knowledge of natural variation in wildlife populations to be able to recognize anthropogenically caused variation

Study of Z Boson Pair Production in e+e- Collisions at LEP at \sqrt{s}=189 GeV

The pair production of Z bosons is studied using the data collected by the L3 detector at LEP in 1998 in e+e- collisions at a centre-of-mass energy of 189 GeV. All the visible final states are considered and the cross section of this process is measured to be 0.74 +0.15 -0.14 (stat.) +/- 0.04 (syst.) pb. Final states containing b quarks are enhanced by a dedicated selection and their production cross section is found to be 0.18 +0.09 -0.07 (stat.) +/- 0.02 (syst.) pb. Both results are in agreement with the Standard Model predictions. Limits on anomalous couplings between neutral gauge bosons are derived from these measurements

Formation of the ηc\eta_c in Two-Photon Collisions at LEP

The two-photon width $\Gamma_{\gamma\gamma}$ of the $\eta_c$ meson has been measured with the L3 detector at LEP. The $\eta_c$ is studied in the decay modes $\pi^+\pi^-\pi^+\pi^-$, $\pi^+\pi^-$K$^+$K$^-$, K$_s^0$K$^\pm\pi^\mp$, K$^+$K$^-\pi^{0}$, $\pi^+\pi^-\eta$, $\pi^+\pi^-\eta'$, and $\rho^+\rho^-$ using an integrated luminosity of 140 pb$^{-1}$ at $\sqrt{s} \simeq 91$ GeV and of 52 pb$^{-1}$ at $\sqrt{s} \simeq 183$ GeV. The result is $\Gamma_{\gamma\gamma}(\eta_c) = 6.9 \pm 1.7 (stat.) \pm 0.8 (sys.) \pm 2.0$(BR) keV. The $Q^2$ dependence of the $\eta_c$ cross section is studied for $Q^2 < 9$ GeV$^{2}$. It is found to be better described by a Vector Meson Dominance model form factor with a J-pole than with a $\rho$-pole. In addition, a signal of $29 \pm 11$ events is observed at the $\chi_c0$ mass. Upper limits for the two-photon widths of the $\chi_c0$, $\chi_c2$, and $\eta_c'$ are also given

Search for Scalar Leptons in e+e- collisions at \sqrt{s}=189 GeV

We report the result of a search for scalar leptons in e+e- collisions at 189 GeV centre-of-mass energy at LEP. No evidence for such particles is found in a data sample of 176 pb^{-1}. Improved upper limits are set on the production cross sections for these new particles. New exclusion contours in the parameter space of the Minimal Supersymmetric Standard Model are derived, as well as new lower limits on the masses of these supersymmetric particles. Under the assumptions of common gaugino and scalar masses at the GUT scale, we set an absolute lower limit on the mass of the lightest scalar electron of 65.5 Ge