Stefan Stolte

Publications of Stefan Stolte

• Hydrolysis of sulphonamides in aqueous solutions.

  Authors: Anna Białk-Bielińska, Stefan Stolte, Marianne Matzke, Aleksandra Fabiańska, Joanna Maszkowska, Marta Kołodziejska, Beata Liberek, Piotr Stepnowski, Jolanta Kumirska

  Journal of hazardous materials. 04/2012;

  Hydrolysis is one of the most common reactions controlling abiotic degradation and is one of the main paths by which substances are degraded in the environment. Nevertheless, the availableHydrolysis is one of the most common reactions controlling abiotic degradation and is one of the main paths by which substances are degraded in the environment. Nevertheless, the available information on this process for many compounds, including sulphonamides (a group of antibiotic drugs widely used in veterinary medicine), is very limited. This is the first study investigating the hydrolytic stabilities of 12 sulphonamides, which were determined according to OECD guideline 111 (1st category reliability data on the basis of regulatory demands on data quality for the environmental risk assessment of pharmaceuticals). Hydrolysis behaviour was examined at pH values normally found in the environment. This was prefaced by a discussion of the acid-base properties of sulphonamides. All the sulphonamides tested were hydrolytically stable at pH 9.0, nine (apart from sulphadiazine, sulphachloropyridazine and sulphamethoxypyridazine) were stable in this respect at pH 7.0 and two (sulphadiazine and sulphaguanidine) at pH 4.0 (hydrolysis rate≤10%; t(0.5 (25°C))>1 year). The degradation products were identified, indicating two independent mechanisms of this process. Our results show that under typical environmental conditions (pH and temperature) sulphonamides are hydrolytically stable with a long half-life; they thus contribute to the on-going assessment of their environmental fate.

• Determination of LFER Descriptors of 30 Cations of Ionic Liquids-Progress in Understanding Their Molecular Interaction Potentials.

  Authors: Chul-Woong Cho, Christian Jungnickel, Stefan Stolte, Ulrich Preiss, Jürgen Arning, Johannes Ranke, Ingo Krossing, Jorg Thöming

  Chemphyschem : a European journal of chemical physics and physical chemistry. 02/2012; 13(3):780-7.

  In order to understand molecular interaction potentials of 30 cations of ionic liquids (ILs), the well-known linear free energy relationship concept (LFER) was applied. The LFER descriptors for theIn order to understand molecular interaction potentials of 30 cations of ionic liquids (ILs), the well-known linear free energy relationship concept (LFER) was applied. The LFER descriptors for the excess molar refractivity and the molar volume were calculated in silico and for hydrogen-bonding acidity and basicity, and the polarizability/dipolarity of IL cations were experimentally determined through high performance liquid chromatography (HPLC) measurements. For the study, three different columns (RP-select B, Cyan, and Diol) and buffered mobile phases, based on two organic solvents acetonitrile (ACN) and methanol (MeOH), were selectively combined to the HPLC separation systems RP-select B-ACN, RP-select B-MeOH, Cyan-MeOH, Diol-ACN, and Diol-MeOH. By measuring the retention factors of 45 neutral calibration compounds and calculating LFER descriptors of three cations in the HPLC systems, the system parameters, including an ionic z coefficient, were determined. Conversely, the LFER descriptors of 30 ionic liquid cations were determined, based on the parameters of five systems and their retention factors in the HPLC systems. The results showed that the type of head group, alkyl chain length and further substituents of the cation have a significant influence on the dipolarity/polarizability and the hydrogen-bonding acidity, and functionalized groups (hydroxyl, ether, and dimethylamino) lead to hydrogen-bonding basicity of the cation. The characterization of cationic LFER descriptors opens up the chance for a more quantitative understanding of molecular interaction potentials and physicochemical properties of ILs.

• Detection of Bioactive Exometabolites Produced by the Filamentous Marine Cyanobacterium Geitlerinema sp.

  Authors: Nelson H Caicedo, Jolanta Kumirska, Jennifer Neumann, Stefan Stolte, Jorg Thöming

  Marine biotechnology (New York, N.Y.). 12/2011;

  Marine cyanobacteria are noted for their ability to excrete metabolites with biotic properties. This paper focuses on such exometabolites obtained from the culture of the marine filamentousMarine cyanobacteria are noted for their ability to excrete metabolites with biotic properties. This paper focuses on such exometabolites obtained from the culture of the marine filamentous cyanobacterium Geitlerinema sp. strain, their purification and subsequent analyses. By this means the recoveries of the active compounds, a prerequisite for properly determining their concentration, are quantified here for the first time. We demonstrate a new procedure using Amberlite XAD-1180 resin in combination with the eluent isopropanol for extraction of the culture media and gas chromatography as simplified chemical analysis. This procedure reduced necessary bacteria cultivation time (from 150 to 21 days) at low volumes of culture media (300 mL) required for identification of two selected bioactive compounds: 4,4'-dihydroxybiphenyl and harmane.

• Influence of microbial adaption and supplementation of nutrients on the biodegradation of ionic liquids in sewage sludge treatment processes.

  Authors: Marta Markiewicz, Stefan Stolte, Zofia Lustig, Justyna Łuczak, Michał Skup, Jan Hupka, Christian Jungnickel

  Journal of hazardous materials. 08/2011; 195:378-82.

  As ionic liquids are winning more attention from industry as a replacement of more hazardous chemicals, some of their structures have the potential to become persistent pollutants due to highAs ionic liquids are winning more attention from industry as a replacement of more hazardous chemicals, some of their structures have the potential to become persistent pollutants due to high stability towards abiotic and biotic degradation processes. Therefore it is important to determine the hazard associated with the presence of ILs in the environment, for example biodegradation under real conditions. Standard biodegradation testing procedures generally permit pre-conditioning of inoculum but do not allow for pre-exposition to the test substance. These are usually conducted in a mineral medium which does not provide additional organic nutrients. Though very valuable, as a point of reference, these tests do not fully represent real conditions. In in situ conditions, for example in wastewater treatment plants or natural soils and water bodies, the presence of readily available sources of energy and nutrients as well as the process of adaptation may often alter the fate and metabolic pathways of xenobiotics. Our results have shown that these are the opposing processes influencing the biodegradation rate of ILs in sewage sludge. The results have significant practical implications with respect to the assessment of biodegradability and environmental fate of ILs and other xenobiotics in environmental conditions and their potential remediation options.

• Ecotoxicity evaluation of selected sulfonamides.

  Authors: Anna Białk-Bielińska, Stefan Stolte, Jürgen Arning, Ute Uebers, Andrea Böschen, Piotr Stepnowski, Marianne Matzke

  Chemosphere. 07/2011; 85(6):928-33.

  Sulfonamides (SAs) are a group of antibiotic drugs widely used in veterinary medicine. The contamination of the environment by these pharmaceuticals has raised concern in recent years. However,Sulfonamides (SAs) are a group of antibiotic drugs widely used in veterinary medicine. The contamination of the environment by these pharmaceuticals has raised concern in recent years. However, knowledge of their (eco)toxicity is still very basic and is restricted to just a few of these substances. Even though their toxicological analysis has been thoroughly performed and ecotoxicological data are available in the literature, a systematic analysis of their ecotoxicological potential has yet to be carried out. To fill this gap, 12 different SAs were chosen for detailed analysis with the focus on different bacteria as well as non-target organisms (algae and plants). A flexible (eco)toxicological test battery was used, including enzymes (acetylcholinesterase and glutathione reductase), luminescent marine bacteria (Vibrio fischeri), soil bacteria (Arthrobacter globiformis), limnic unicellular green algae (Scenedesmus vacuolatus) and duckweed (Lemna minor), in order to take into account both the aquatic and terrestrial compartments of the environment, as well as different trophic levels. It was found that SAs are not only toxic towards green algae (EC₅₀=1.54-32.25 mg L⁻¹) but have even stronger adverse effect on duckweed (EC₅₀=0.02-4.89 mg L⁻¹) than atrazine - herbicide (EC₅₀=2.59 mg L⁻¹).

• Ionic liquids: predictions of physicochemical properties with experimental and/or DFT-calculated LFER parameters to understand molecular interactions in solution.

  Authors: Chul-Woong Cho, Ulrich Preiss, Christian Jungnickel, Stefan Stolte, Jürgen Arning, Johannes Ranke, Andreas Klamt, Ingo Krossing, Jorg Thöming

  The journal of physical chemistry. B. 05/2011; 115(19):6040-50.

  In this article, we present evolutionary models to predict the octanol-water partition coefficients (log P), water solubilities, and critical micelle concentrations (CMCs) of ionic liquids (ILs), asIn this article, we present evolutionary models to predict the octanol-water partition coefficients (log P), water solubilities, and critical micelle concentrations (CMCs) of ionic liquids (ILs), as well as the anionic activity coefficients and hydrophobicities in pure water and octanol-water. They are based on a polyparameter linear free energy relationship (LFER) using measured and/or DFT-calculated LFER parameters: hydrogen-bonding acidity (A), hydrogen-bonding basicity (B), polarizability/dipolarity (S), excess molar refraction (E), and McGowan volume (V) of IL ions. With both calculated or experimental LFER descriptors of IL ions, the physicochemical parameters were predicted with an errors of 0.182-0.217 for the octanol-water partition coefficient and 0.131-0.166 logarithmic units for the water solubility. Because experimentally determined solute parameters of anions are not currently available, the CMC, anionic activity coefficient, and hydrophobicity were predicted with quantum-chemical methods with R(2) values of at least 0.99, as well as errors below 0.168 logarithmic units. These new approaches will facilitate the assessment of the technical applicability and environmental fate of ionic compounds even before their synthesis.

• Thinking in Terms of Structure-Activity-Relationships (T-SAR): A Tool to Better Understand Nanofiltration Membranes

  Authors: José F. Fernández, Bernd Jastorff, Reinhold Störmann, Stefan Stolte, Jorg Thöming

  Membranes. 01/2011; 1:162-183.

  A frontier to be conquered in the field of membrane technology is related to the very limited scientific base for the rational and task-specific design of membranes. This is especially true forA frontier to be conquered in the field of membrane technology is related to the very limited scientific base for the rational and task-specific design of membranes. This is especially true for nanofiltration membranes with properties that are based on several solute-membrane interaction mechanisms. “Thinking in terms of Structure-Activity-Relationships” (T-SAR) is a methodology which applies a systematic analysis of a chemical entity based on its structural formula. However, the analysis become more complex with increasing size of the molecules considered. In this study, T-SAR was combined with classical membrane characterization methods, resulting in a new methodology which allowed us not only to explain membrane characteristics, but also provides evidence for the importance of the chemical structure for separation performance. We demonstrate an application of the combined approach and its potential to discover stereochemistry, molecular interaction potentials, and reactivity of two FilmTec nanofiltration membranes (NF-90 and NF-270). Based on these results, it was possible to predict both properties and performance in the recovery of hydrophobic ionic liquids from aqueous solution.

• Permeation through nanochannels: revealing fast kinetics.

  Authors: Kozhinjampara R Mahendran, Pratik Raj Singh, Jürgen Arning, Stefan Stolte, Ulrich Kleinekathöfer, Mathias Winterhalter

  Journal of physics. Condensed matter : an Institute of Physics journal. 11/2010; 22(45):454131.

  The permeation of water soluble molecules across cell membranes is controlled by channel-forming proteins and, in particular, the channel surface determines the selectivity. An adequate method toThe permeation of water soluble molecules across cell membranes is controlled by channel-forming proteins and, in particular, the channel surface determines the selectivity. An adequate method to study the properties of these channels is electrophysiology and, in particular, analyzing the ion current fluctuation in the presence of permeating solutes. Ion current fluctuation analysis provides information on possible interactions of solutes with the channel surface. Due to the limited time resolution, fast permeation events are not visible using standard techniques. Here, we demonstrate that miniaturization of the lipid bilayer; varying the temperature or changing the solvent may enhance the resolution. Although electrophysiology is considered as a single molecule technique, it does not provide atomic resolution. Molecular details of solute permeation can be revealed by combining electrophysiology and all-atom computer modeling; these methods include ion conductance, selectivity, ion pair formation, and rate limiting interactions of the solute with the channel walls during permeation.

• Analyzing Cytotoxic Effects of Selected Isothiazol-3-one Biocides Using the Toxic Ratio Concept and Structure-Activity Relationship Considerations.

  Authors: Jürgen Arning, Marianne Matzke, Stefan Stolte, Frauke Nehen, Ulrike Bottin-Weber, Andrea Böschen, Salha Abdulkarim, Bernd Jastorff, Johannes Ranke

  Chemical research in toxicology. 11/2009;

  To demonstrate how baseline toxicity can be separated from other more specific modes of toxic action and to address possible pitfals when dealing with hydrophobic substances, the fourTo demonstrate how baseline toxicity can be separated from other more specific modes of toxic action and to address possible pitfals when dealing with hydrophobic substances, the four isothiazol-3-one biocides N-methylisothiazol-3-one (MIT), 5-chloro-N-methylisothiazol-3-one (CIT), N-octylisothiazol-3-one (OIT), and 4,5-dichloro-N-octylisothiazol-3-one (DCOIT) as an example for reactive electrophilic xenobiotics were tested for their cytotoxic effects on the human hepatoblastoma cell line Hep G2, on the marine bacterium Vibrio fischeri, and on the limnic green alga Scenedesmus vacuolatus. In each of the three test systems, toxic effects were observed in a consistent pattern. The two chlorinated compounds and OIT were found to be significantly more toxic than MIT. As compared to baseline toxicants, the small and polar MIT and CIT exhibited pronounced excess toxicity in each of the three test systems that is presumably triggered by their intrinsic reactivity toward cellular thiols. In contrast, OIT and DCOIT showed mainly toxicities that could be explained by their hydrophobicity. Analyzing and comparing these results using the toxic ratio concept and with data that indicate a dramatic depletion of cellular glutathione levels after incubation with DCOIT reveals that for highly hydrophobic substances, baseline level toxicity in an assay for acute toxicity can lead to an oversight of other more specific modes of toxic action that may cause significant effects that might be less reversible than those caused by unreactive baseline toxicants. This possibility should be taken into account in the hazard assessment of chemicals that are both hydrophobic and reactive.

• Ionic liquids in soils: effects of different anion species of imidazolium based ionic liquids on wheat (Triticum aestivum) as affected by different clay minerals and clay concentrations.

  Authors: Marianne Matzke, Stefan Stolte, Jürgen Arning, Ute Uebers, Juliane Filser

  Ecotoxicology (London, England). 11/2008;

  This study contributes to a prospective hazard assessment of ionic liquids, focusing on the terrestrial environment. The influence of differently composed soils-varying contents of the clay mineralsThis study contributes to a prospective hazard assessment of ionic liquids, focusing on the terrestrial environment. The influence of differently composed soils-varying contents of the clay minerals smectite and kaolinite-on the toxicity of different anion species of imidazolium based ionic liquids was studied for growth inhibition of wheat (Triticum aestivum). IM14 (CF(3)SO(2))(2)N appeared the most toxic, independently of the investigated soil type. The toxicity of IM14 Cl, IM14 BF(4) and IM14 HSO(4) was mainly dominated by the cationic moiety. The observed effects varied in dependence of the added clay type and clay concentration. An increase of clay content resulted in less pronounced effects of these substances. In contrast, for IM14 (CF(3)SO(2))(2)N the addition of clay minerals caused higher toxic effects in comparison to the reference soil. Our results give first hints for the assumption, that ionic liquids whose toxic action is based on the anionic moiety are especially hazardous for soils, particular for soils with high clay contents.

• Structure-activity relationships for the impact of selected isothiazol-3-one biocides on glutathione metabolism and glutathione reductase of the human liver cell line Hep G2.

  Authors: Jürgen Arning, Ralf Dringen, Maike Schmidt, Anette Thiessen, Stefan Stolte, Marianne Matzke, Ulrike Bottin-Weber, Birgit Caesar-Geertz, Bernd Jastorff, Johannes Ranke

  Toxicology. 05/2008; 246(2-3):203-12.

  To investigate the toxic mode of action of isothiazol-3-one biocides the four compounds N-methylisothiazol-3-one (MIT), 5-chloro-N-methylisothiazol-3-one (CIT), N-octylisothiazol-3-one (OIT) andTo investigate the toxic mode of action of isothiazol-3-one biocides the four compounds N-methylisothiazol-3-one (MIT), 5-chloro-N-methylisothiazol-3-one (CIT), N-octylisothiazol-3-one (OIT) and 4,5-dichloro-N-octylisothiazol-3-one (DCOIT) were purified and tested as single chemical entities for their effects on the human hepatoblastoma cell line Hep G2 and on isolated and cellular glutathione reductase GR). The two chlorinated substances CIT and DCOIT significantly decreased the amount of total cellular glutathione (GSx) in a dose and time dependent manner. Concomitantly, an increase in the level of oxidised glutathione (GSSG) was observed. The resulting shift in the GSH/GSSG ratio entailing the breakdown of the cellular thiol reduction potential was accompanied by necrotic morphological changes like swelling of the plasma membrane and subsequent lysis of the cells. Additionally, CIT and DCOIT were found to inhibit cellular GR in the cells in a concentration dependent manner. The T-SAR-based (thinking in terms of structure-activity relationships) comparison of the chlorine-substituted structures CIT and DCOIT with their non-chlorinated and less active analogues MIT and OIT identified the chlorine substituents and the resulting reaction mechanisms to be the key structural mediators of the observed toxic effects. Furthermore, differences in the activity of both chlorinated substances could be explained using the T-SAR approach to link the lipophilicity and the intrinsic glutathione-reactivity of the compounds to the expected target site concentrations inside the cells.

• Lipophilicity parameters for ionic liquid cations and their correlation to in vitro cytotoxicity.

  Authors: Johannes Ranke, Anja Müller, Ulrike Bottin-Weber, Frauke Stock, Stefan Stolte, Jürgen Arning, Reinhold Störmann, Bernd Jastorff

  Ecotoxicology and environmental safety. 08/2007; 67(3):430-8.

  Regarding the great structural variability of the currently expanding group of ionic liquids, it is highly desirable to understand the basic factors affecting their toxicity in different biologicalRegarding the great structural variability of the currently expanding group of ionic liquids, it is highly desirable to understand the basic factors affecting their toxicity in different biological systems. The present study of a set of 74 ionic liquids with imidazolium, pyrrolidinium, pyridinium, quinolinium, quaternary phosphonium and quaternary ammonium cations and the comparatively small anions Cl(-), Br(-), BF(4)(-), or PF(6)(-) demonstrates the influence of the cation lipophilicity on the cytotoxicity in IPC-81 leukemia cells from rats. The scope of this correlation is limited to ionic liquids with these or similarly small anions that are sufficiently nonreactive under physiological and chromatographic conditions and whose cation lipophilicity does not exceed a certain threshold.

• Progress in evaluation of risk potential of ionic liquids—basis for an eco-design of sustainable products

  Authors: Bernd Jastorff, Kerstin Mölter, Peter Behrend, Ulrike Bottin-Weber, Juliane Filser, Anna Heimers, Bernd Ondruschka, Johannes Ranke, Maike Schaefer, Heike Schröder, Annegret Stark, Piotr Stepnowski, Frauke Stock, Reinhold Störmann, Stefan Stolte ...

  Green Chemistry. 01/2005; 7:362-372.

  Motivated by the prevailing need for a sustainable development and taking the principles of Green Chemistry as a starting point, the present paper describes new and updated findings regarding aMotivated by the prevailing need for a sustainable development and taking the principles of Green Chemistry as a starting point, the present paper describes new and updated findings regarding a sustainable product design for ionic liquids. The focus is on environmental risk. Nevertheless, cytotoxicity testing and first indicative results from a genotoxicity study extend present knowledge also with regard to possible effects on humans. The structural variability of commercially available ionic liquids as well as the abundance of theoretically accessible ionic liquids is illustrated and the consequences for an integrated risk assessment accompanying the development process are discussed. The side chain effect on toxicity for imidazolium type ionic liquids was confounded by more complex biological testing. Also, an influence of an anion on cytotoxicity is shown for the first time. Testing of presumed metabolites of the imidazolium type cations showed a significantly lower biological activity in cytotoxicity studies than their parent compounds. The importance of a purity assessment for ionic liquids is pointed out and a collection of methods that is believed to be adequate is presented. In addition to risk analysis, the use of life cycle analysis for the multi-objective problem of designing ionic liquids is sketched and an eco-design scheme for ionic liquids is proposed. In conclusion, the paper illustrates the complex nature of the development processes ionic liquids are currently undergoing and provides guidance on which aspects have to be kept in mind.