Computational understanding and experimental characterization of twice-as-smart quadruplex ligands as chemical sensors of bacterial nucleotide second messengers

A twice-as-smart ligand is a small molecule that experiences a structural switch upon interaction with its target (i.e., smart ligand) that concomitantly triggers its fluorescence(i.e., smart probe). Prototypes of twice-as-smart ligands were recently developed to track and label G-quadruplexes: these higher-order nucleic acid structures originate in the assembly of four guanine(G)-rich DNA or RNA strands, whose stability is imparted by the formation and the self-assembly of G-quartets. The firstprototypes of twice-as-smart quadruplex ligands were designed to exploit the self-association of quartets, being themselves synthetic G-quartets. While their quadruplex recognition capability has been thoroughly documented, some doubts remain about the precise photophysical mechanism that underlies their peculiar spectroscopic properties. Here, we uncovered this mechanism via complete theoretical calculations. Collected information was then used to develop of a novel application of twice-as-smart ligands, as efficnt chemical sensors of bacterial signaling pathways via the fluorescentdetection of naturally occurring extracellular quadruplexes formed by cyclic dimeric guanosine monophosphate (c-di-GMP)

Homogeneous Gold Catalysis through Relativistic Effects: Addition of Water to Propyne

In the catalytic addition of water to propyne the Au(III) catalyst is not stable under non-relativistic conditions and dissociates into a Au(I) compound and Cl2. This implies that one link in the chain of events in the catalytic cycle is broken and relativity may well be seen as the reason why Au(III) compounds are effective catalysts.Comment: 12 pages, 3 figures, 1 tabl

Statistical Results and Implications of the Enchytraeid Reproduction Ringtest.

Abstract not availableJRC.I-Institute for Health and Consumer Protection (Ispra

Organisation and performance of an international ringtest for the validation of the Enchytraeid reproduction test. Vol. 1 and 2. Organisation und Durchfuehrung eines internationalen Ringtests zur Validierung des Enchytraeen Reproduktionstests. Vol. 1 und 2

The aim of the project was the organisation and performance of an international Ringtest for the Enchytraeid Reproduction Test (ERT) which was developed on behalf of the German Federal Environmental Agency (UBA) several years ago. An existing Draft Guideline presented during a workshop in Bad Soden (Germany) in 1995 was used to run the test. A total of 29 institutions (governmental agencies, universities, contract laboratories, and industry) from 15 different countries participated in the Ringtest. Most participants performed four test. Two of these tests were conducted with the fungicide Carbendazim (Formulation Derosal) and two with 4-Nitrophenol. For each chemical one test was designed according to an ECx approach and the other according to a NOEC approach. Several courses and workshops were organised to inform and train the participants. Six Ringtest newsletters (RTL) were prepared and distributed to all participants during the project. A task force consisting of 6 members supported the organisation of the Ringtest. A major aspect of the project was the detailed statistical evaluation of the test results. Additionally, these results are thought to be an important contribution to the recent discussion on ecotoxicological test design. As a result of the Ringtest, the ERT Draft Guideline, which losely follows formal requirements of the OECD test guidelines programme, was significantly improved. (orig.)SIGLEAvailable from TIB Hannover: RN 8422(1999,4) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Umwelt, Naturschutz und Reaktorsicherheit, Bonn (Germany)DEGerman

Arbeiten zur Uebertragbarkeit und Praezisierung der Wirkungsmechanismen chemischer Belastung in verschiedenen Oekosystemen. Teilprojekt 2: Zoologische und mikrobiologische Parameter zum Streuabbau Abschlussbericht

Available from TIB Hannover: F95B83+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman

Umweltprobleme durch Arzneimitteln. Literaturstudie

The subject of the study was to examine whether the ecotoxicological hazard potential of pharmaceuticals or their metaboloties should be assessed. In a first step, publications on environmental problems known to be related to pharmaceuticlas were reviewed and evaluated. The data were discussed with concerned interest groups. In a second step, the data required by the 'Arzneimittelgesetz (AMG)' as part of the registration process were assessed under the aspect of suitability for ecotoxicological risk assessment. Additionally, it was evaluated which laboratory tests should be required to perform ecotoxicological risk assessments with pharmaceuticals. Preliminary risk assessments were conducted for different pharmaceutical groups if sufficient data were available. Taking into consideration the legal requirements for chemical notification within the EU, the necessity of further development of the AMG concerning ecotoxicological aspects was emphasized. (orig.)Available from TIB Hannover: RN 8422(1996,60) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Umwelt, Naturschutz und Reaktorsicherheit, Bonn (Germany)DEGerman

Standardisierung und Validierung eines Bioakkumulationstests mit terestrischen Oligochaeten

SIGLEAvailable from TIB Hannover: RN 8908(2000,205) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Umwelt, Naturschutz und Reaktorsicherheit, Bonn (Germany)DEGerman

Entwicklung und Erprobung eines Bioakkumulationstests mit endobenthischen Organismen

The presented study describes a standardised method for measuring the bioaccumulation of sediment-associated chemicals in endobenthic animals. The tubificid oligochaetes Tubifex tubifex and Limnodrilus hoffmeisteri represent the benthic infauna. Lindane and Hexachlorobenzene (HCB) were chosen as model substances. They were applied in a "1"4C-radiolabelled form. Uptake, depuration and the resulting bioaccumulation factors (BAF) were determined. The results were compared with the corresponding fish-bioconcentration factors (BCF). "1"4C-Lindane was accumulated in the tubificids by a factor of 4.7 (mean value; n=4). "1"4C-HCB reached a BAF of 6.6 (n=4) in both test species. These BAF values are based on wet weight and radioactive concentrations. Lindane was taken up faster than HCB. When transferred to clean sediment the worms eliminated both test substances rapidly and nearly completely. No major metabolites were detected in worms, sediment and water. The applied kinetic model equations fitted to the data using non-linear regression analysis showed a good fit. The determined BAF values of "1"4C-Lindane and "1"4C-HCB are orders of magnitude below the corresponding fish-BCF values. Nevertheless, the tubificid body burdens resulting from exposure to contaminated sediment can reach notably higher body burdens than fish body burdens resulting from exposure to the water phase only. The presented data show that the assessment of bioaccumulation based exclusively on the extrapolation of fish-BCF to other organisms and environmental compartments is not appropriate. A draft guideline for the determination of bioaccumulation in endobenthic animals according to OECD format (comparable to the OECD-Guideline No. 305 for testing the bioconcentration of chemicals in fish from water) is presented. (orig.)SIGLEAvailable from TIB Hannover: RN 8422(1999,2) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Umwelt, Naturschutz und Reaktorsicherheit, Bonn (Germany)DEGerman

The performance of Fraxinus angustifolia as a helper for metal phytoremediation programs and its relation to the endophytic bacterial communities

Soil contamination with metals is a serious problem requiring urgent measures to counteract their impacts. The conventional soil remediation techniques are often inefficient and expensive. In this work, we studied the potential of the species Fraxinus angustifolia for the phytoremediation of metal contaminated soils from the Cunha Baixa uranium mine (Mangualde, Portugal). The plants were exposed to a contaminated, a reference and a control soil, for a period of about 3months, during which metal accumulation and a set of physiologic parameters (shoot height, potential maximum efficiency of PSII (Fv/Fm) and quantum yield of PSII (ΦPSII), leaf area, specific leaf area, leaf relative water content, leaf chlorophyll a, chlorophyll b and carotenoid content, leaf malondialdehyde (MDA) content and leaf proline content) were measured. The genetic profiles of the endophytic communities from the roots of the plants were also analyzed, via PCR-Denaturing Gradient Gel Electrophoresis (DGGE) targeted for a conserved region of 16S rDNA, pre- and post-exposure. Only the shoot height was a suitable indicator of the negative effects of the contamination with metals on the plants. The remaining parameters indicated good physiologic fitness and recovery. The trees did not hyperaccumulate metals but extracted Sr at a higher rate. The bacterial profiles from the control and reference soils showed more similarity with each other and with the pre-exposure profiles than with those from the contaminated soil. We showed that F. angustifolia has the ability to resist and adapt to the adverse conditions of contamination, revealing a potential which can be exploited for phytoremediation, specifically phytostabilization. It also revealed that changes exerted on the bacterial root communities exposed to contamination, resulted in profiles considerably different from those of the remaining communities.This work was carried out under a project funded by the North Atlantic Treaty Organization (NATO), within the Program Science for Peace (Ref. SfP. 983311). This study was also partially funded by FSE and POPH funds (Programa Ciência 2007).publishe