University of Kaiserslautern
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Metabolic Activation of 2-Methylfuran to Acetylacrolein and Its Reactivity toward Cellular Proteins
Get PDF2-Methylfuran (2-MF) is a process-related contaminant found primarily in heat-treated foods, such as coffee or canned food. The oxidative metabolic activation of 2-MF is supposed to follow the pathway established for furan, which is known to generate the highly reactive metabolite butenedial (BDA). In the case of 2-MF, generation of the BDA homologue 3-acetylacrolein (AcA) is to be expected. 2-MF metabolism to AcA was investigated in two model systems: commercial microsomal preparations and primary rat hepatocytes (pRH). To scavenge the generated 2-MF, two model nucleophils, N-acetyl-l-cysteine (AcCys) and N-α-acetyl-l-lysine (AcLys), were used, and the formation of the corresponding adducts was measured in the supernatants. The metabolic activation of 2-MF to AcA was studied using human liver microsomes as well as rat liver microsomes. Incubation of 2-MF in Supersomes allowed to identify the cytochrome P450 isoenzyme primarily responsible for 2-MF. In addition, primary rat hepatocytes were incubated with 2-MF or AcA and AcLys adduct of AcA (N-α-acetyl-l-lysine-acetylacrolein, AcLys-AcA) determined in the cell supernatants by UHPLC-MS/MS. In model experiments, AcA formed adducts with AcCys and AcLys. The structures of both adducts were characterized. For incubations in biological activating systems, CYP 2E1 was found to be a key enzyme for the conversion of 2-MF to AcA in Supersomes. When pRH were incubated with 2-MF and AcA, AcLys-AcA was detected in the cell supernatants in a time- and dose-dependent manner. The results showed that AcA was indeed formed at the cellular level. In contrast to the AcLys-AcA adduct, no N-acetyl-l-cysteine-acetylacrolein (AcCys-AcA) adduct could be detected in pRH. AcA was determined as a reactive metabolite of 2-MF in vitro, and its adduct formation with nucleophilic cellular components was evaluated. The metabolites were characterized, and AcLys-AcA was identified as potential biomarker
Development and Validation of Efficient Multifluid and Population Balance Models for Dispersed Gas-Liquid Processes
Get PDFReactive multiphase systems, in which at least one phase is dispersed, are ubiquitous in chemical and biotechnological processes.
The complexity of these systems, involving multiple interacting phases and a wide range of process conditions, presents significant challenges to experimental analysis alone.
Consequently, there is a need for reliable and computationally efficient models to predict system behavior, optimize reactor design, and facilitate process scale-up from laboratory to production scale.
This thesis develops and validates novel models for three reactor types: jet loop reactors (JLRs), bubble columns (BCs), and stirred tank reactors (STRs).
For JLRs, a one-dimensional momentum balance model was developed that allows local resolution of key process variables.
This model revealed significant effects of gas consumption on internal circulation and reactor performance.
For BCs, a one-dimensional multifluid population balance model (MPB) was developed.
The model accurately predicts gas holdup and the bubble size distribution using a one-point calibration.
The prediction performance was evaluated on the basis of new experimental data encompassing the variation of gas and liquid fluxes, design of gas sparger, liquid holdup and liquid composition.
However, limitations are apparent at higher gas and liquid fluxes.
The thesis also addresses converting a number-based population balance equation (PBE) to a mass-based PBE, introducing a mass transfer term that enhances the understanding of the conservation properties of the PBE.
Finally, the MPB was applied to a non-reactive semi-batch STR.
A newly proposed finite volume method with Gauss quadrature (FVMG) was found to be fast, robust, and accurate compared to other numerical methods.
In a parameter and sensitivity study, most trends from the literature could be confirmed.
Preliminary experimental validation showed good agreement with simulation results, although further work is needed to generalize the model.
The models developed offer computationally efficient tools for extensive parameter studies, enhancing the understanding of dispersed multiphase reactive processes, essential for reactor design and optimization.Reaktive Mehrphasensysteme, bei denen mindestens eine Phase dispergiert ist, sind in chemischen und biotechnologischen Prozessen weit verbreitet.
Die Komplexität dieser Systeme, die mehrere interagierende Phasen und eine Vielzahl von Prozessbedingungen umfasst, stellt eine große Herausforderung für die experimentelle Analyse dar.
Daher besteht ein Bedarf an zuverlässigen und rechnerisch effizienten Modellen, um das Systemverhalten vorherzusagen, die Reaktorkonstruktion zu optimieren und die Prozessskalierung vom Labor- auf den Produktionsmaßstab zu erleichtern.
In dieser Arbeit werden solche Modelle für drei Reaktortypen entwickelt und validiert: Strahlschlaufenreaktoren (JLRs), Blasensäulen (BCs) und Rührkesselreaktoren (STRs).
Für JLRs wurde ein eindimensionales Impulsbilanzmodell entwickelt, das eine lokale Auflösung der wichtigsten Prozessvariablen ermöglicht.
Dieses Modell zeigte signifikante Auswirkungen einer gasverbrauchenden Reaktion auf die interne Zirkulation und die Reaktorleistung.
Für Blasensäulen wurde ein eindimensionales Multifluid-Populationsbilanzmodell (MPB) entwickelt.
Das Modell ermöglicht eine effektive und genaue Vorhersage des Gasanteils und der Blasengrößenverteilung mithilfe einer Ein-Punkt- Kalibrierung.
Die Vorhersagekraft wurde anhand neuer experimenteller Daten bewertet, die die Variation von Gas- und Flüssigkeitsströmen, des Designs des Gasverteilers, des Flüssigkeitsanteils und der Flüssigkeitszusammensetzung umfassten.
Allerdings zeigen sich Einschränkungen bei höheren Gas- und Flüssigkeitsströmen.
Darüber hinaus befasst sich diese Arbeit mit der Transformation einer anzahlbasierten Populationsbilanzgleichung (PBE) in eine massenbasierte PBE, wobei ein Massentransfer-Term eingeführt wurde, der das Verständnis der Erhaltungseigenschaften der PBE verbessert.
Schließlich wurde das MPB auf einen nicht-reaktiven semi-batch STR angewendet.
Eine neu vorgeschlagene Finite Volumen Methode mit Gauss-Quadratur (FVMG) erwies sich im Vergleich zu anderen numerischen Methoden als schnell, robust und genau.
In einer Parameter- und Sensitivitätsstudie konnten die meisten Trends aus der Literatur bestätigt werden.
Eine vorläufige experimentelle Validierung zeigte eine gute Übereinstimmung mit den Simulationsergebnissen, obwohl weitere Arbeiten erforderlich sind, um das Modell zu verallgemeinern.
Die entwickelten Modelle bieten rechnerisch effiziente Werkzeuge für umfangreiche Parameterstudien und verbessern das Verständnis von dispergierten mehrphasigen reaktiven Prozessen, welches für die Reaktorkonstruktion und -optimierung unerlässlich ist
Cohomological connectivity of perturbations of map-germs
Get PDFLet be a finite map-germ with and the image of a small perturbation . We show that the reduced cohomology of is concentrated in a range of degrees determined by the dimension of the instability locus of . In the case , we obtain an analogous result, replacing finiteness by -finiteness and by the discriminant . We also study the monodromy associated to the perturbation
Plant-specific factors affecting short-range attraction and oviposition of European grapevine moths
Get PDFThe spread of pests and pathogens is increasingly intensified by climate change and globalization. Two of the most serious insect pests threating European viticulture are the European grape berry moth, Eupoecilia ambiguella (Hübner) and the European grapevine moth Lobesia botrana (Denis & Schiffermüller). Larvae feed on fructiferous organs of grapevine Vitis vinifera, resulting in high yield and quality losses. Under the aspects of integrated pest management, insecticide measures are only reasonable when other control strategies become ineffective. In order to support the development of novel decision support system for the application of insecticides, the aim of this thesis was to decipher plant-specific factors, which affect the short-range attraction and oviposition of L. botrana and E. ambiguella.
The focus was set on the visual, volatile, tactile and gustatory stimuli provided by their host plant after settlement. The use of artificial surfaces as model plant showed that oviposition of both species is affected by the color, the shape and the texture of the oviposition site. To explain a susceptibility of certain grapevine cultivars and phenological stages of the berries to egg infestations, we analysed and compared the chemical composition of the epicuticular waxes of the berry surface as well as the volatile organic compounds emitted by the berries. Thereby it turned out that the attractiveness to wax extracts decreased during ripening of the berries, highlighting a preference of earlier phenological stages of the berries for oviposition. In addition, grapevine cultivars exhibited variations in their volatile composition. The principle components perceived by female’s antennae could not explain the differentiation between cultivars, suggesting volatiles do not trigger orientation to certain cultivars. Furthermore, a method was developed to measure real-time behavioural response of female moths to volatiles. The setup allowed to quantify the orientation to a volatile source as well as movements of the antennae and ovipositor. They could be linked to the olfactory and gustatory perception of volatiles during the evaluation of suitable host plants for oviposition. In addition, the risk of potential alternative host plants in the vicinity of the vineyard was investigated. This confirmed that L. botrana in particular prefers the stimuli provided by some plants to those of grapevine. Overall, the results suggest that during oviposition, volatiles emitted by the plants and the composition of the plant surface are the most important factors for host plant differentiation
The ER-SURF pathway uses ER-mitochondria contact sites for protein targeting to mitochondria
Get PDFMost mitochondrial proteins are synthesized on cytosolic ribosomes and imported into mitochondria in a post-translational reaction. Mitochondrial precursor proteins which use the ER-SURF pathway employ the surface of the endoplasmic reticulum (ER) as an important sorting platform. How they reach the mitochondrial import machinery from the ER is not known. Here we show that mitochondrial contact sites play a crucial role in the ER-to-mitochondria transfer of precursor proteins. The ER mitochondria encounter structure (ERMES) and Tom70, together with Djp1 and Lam6, are part of two parallel and partially redundant ER-to-mitochondria delivery routes. When ER-to-mitochondria transfer is prevented by loss of these two contact sites, many precursors of mitochondrial inner membrane proteins are left stranded on the ER membrane, resulting in mitochondrial dysfunction. Our observations support an active role of the ER in mitochondrial protein biogenesis
Stability and sensitivity of interacting fermionic superfluids to quenched disorder
Get PDFThe microscopic pair structure of superfluids has profound consequences on their properties. Delocalized pairs are predicted to be less affected by static disorder than localized pairs. Ultracold gases allow tuning the pair size via interactions, where for resonant interaction superfluids show largest critical velocity, i.e., stability against perturbations. The sensitivity of such fluids to strong, time-dependent disorder is less explored. Here, we investigate ultracold, interacting Fermi gases across various interaction regimes after rapid switching optical disorder potentials. We record the ability for quantum hydrodynamic expansion of the gas to quantify its long-range phase coherence. Contrary to static expectations, the Bose-Einstein condensate (BEC) exhibits significant resilience against disorder quenches, while the resonantly interacting Fermi gas permanently loses quantum hydrodynamics. Our findings suggest an additional absorption channel perturbing the resonantly interacting gas as pairs can be directly affected by the disorder quench
Aquatic contaminants reduce the quantity and nutritional quality of aquatic subsidy to riparian consumers
Get PDFNeighboring ecosystems are connected by fluxes of organic and inorganic matter. At the aquatic-terrestrial interface, researchers have primarily focused on the magnitude of resource fluxes, while largely disregarding differences in their nutritional quality for consumers in the recipient ecosystem. Aquatic resources, such as emergent aquatic insects, contain substantially higher levels of physiologically important long-chain polyunsaturated fatty acids (long-chain PUFA) than terrestrial resources. Since animals cannot typically biosynthesize long-chain PUFA in quantities sufficient to meet their physiological demands, they must obtain these compounds through their diet. Aquatic subsidy by emergent aquatic insects can therefore benefit the physiological condition and breeding success of riparian consumers such as birds and spiders. However, aquatic contaminants may disrupt aquatic insect emergence, altering the quantity and nutritional quality of aquatic subsidy to recipient terrestrial systems. Despite its importance to local consumers, effects of aquatic contaminants on this process are poorly studied and understood. The primary aim of this thesis is therefore to assess the effects of aquatic contaminants on aquatic-to-terrestrial subsidy, focusing on FA fluxes, and to determine whether shifts in subsidy quality affect riparian consumers. Effects were examined in a set of complex laboratory bioassays that also considered environmental factors (e.g., basal food resource) to increase environmental relevance.
Metals (i.e., cadmium, Cd and copper, Cu) substantially reduced aquatic insect emergence (up to 95%) and the flux of physiologically important long-chain PUFA (up to 80%) while being efficiently excreted during metamorphosis (reduction by ~90%). Given their relative scarcity in terrestrial ecosystems, local consumers may be particularly vulnerable to changes in the flux of physiologically important long-chain PUFA. Indeed, contaminant-induced alterations of aquatic subsidy quality can affect the physiological condition of riparian spiders, as suggested by a consistent decline in spider growth (40-50%), irrespective of the contaminant group (Cu, Bacillus thuringiensis var. israelensis (Bti) or a mixture of synthetic pesticides) to which their prey was exposed. Since spider neutral lipid FA contents were only reduced in two out of three contaminant treatments compared to the control (up to ~30%, Cu and Bti), this implies contaminant-dependent effect pathways modifying the transfer of energy within food webs at the aquatic-terrestrial interface. Furthermore, results from a multigeneration experiment point to a relatively constant reduction in aquatic insect emergence and thus sustained alteration in the aquatic-to-terrestrial subsidy. Finally, the basal resource quality and sex-specific differences in aquatic insects and terrestrial consumers may further complicate the assessment of contaminant-induced effects. This thesis therefore recommends to consider fluxes of long-chain PUFA to better understand and anticipate implications of aquatic contaminants on the aquatic-terrestrial meta-ecosystem and develop efficient measures to protect riparian systems and their communities
Sustainability of permaculture farming
Get PDFSince its emergence approximately 10 000 years ago, agriculture has formed human lifestyle and facilitated the rise of complex civilizations. At the same time it led to the development of social inequality and allowed the overexploitation of natural resources. These processes in combination with climatic changes and a growing population resulted in the collapse of various advanced civilizations in human history. Today, we face a similar situation with a climate change for which we ourselves are responsible, despite our ability to understand what led to the collapse of past civilizations and to predict future developments.
Modern industrial agriculture largely contributes to threatening environmental issues like climate change, soil degradation and biodiversity loss. Agroecology and permaculture have emerged as sustainable alternatives. While agroecology is a well-established scientific discipline, permaculture focuses on the conscious design of resilient agroecosystems that mimic nature. The second chapter reviews the scientific basis of permaculture's design principles, as proposed by co-founder David Holmgren. We find that permaculture not only builds on scientific evidence but also aligns with agroecological principles and offers additional guidelines for creating resilient farming systems.
However, empirical evidence supporting permaculture’s benefits has been sparse. Therefore, we conducted two studies on commercial permaculture sites in Central Europe to examine the effectiveness of permaculture in both environmental sustainability and crop productivity. The first study examined a wide range of soil and biodiversity indicators on nine permaculture sites. The study found that permaculture sites had 27% higher soil carbon storage, 20% lower soil bulk density, and a 201% increase in earthworm abundance compared to direct control fields of predominant industrial agriculture. Additionally, levels of various soil macro- and micronutrients were higher on permaculture sites, indicating better conditions for crop production. Species richness for vascular plants, earthworms, and birds was also significantly higher on permaculture sites, with increases of 457%, 77%, and 197%, respectively. The second study, focused on the crop productivity of eleven permaculture sites. Using the Land Equivalent Ratio (LER) as an index, the study found that the yields from permaculture sites were comparable to those of industrial agriculture. Specifically, the LER for permaculture was 0.80 ± 0.27 when compared to total German agriculture and 1.44 ± 0.52 when compared to German organic agriculture, both with no significant difference to 1. Together, these studies suggest that permaculture not only offers environmental benefits but also holds promise in terms of crop productivity.
These findings align well with global initiatives such as the "4 per 1000" initiative, the United Nations Decade on Ecosystem Restoration and the United Nations Sustainable Development Goals. Despite promising results, variability in outcomes suggests the need for further research to understand the complex factors influencing permaculture's effectiveness. Further, we advocate for a multi-dimensional approach to large-scale implementation, involving financial restructuring, educational reforms, and the initiation of flagship projects. Given the urgency of environmental crises, we argue that immediate action is imperative, with research serving as a tool for continuous improvement rather than a prerequisite for action
Die Bestimmung von Gesundheitsgefahren durch krebserzeugende Luftschadstoffe und deren Bewältigung in der Bauleitplanung
Get PDFKrebserzeugende Luftschadstoffe stellen eine erhebliche Gesundheitsgefahr dar. Die Arbeit untersucht, welchen Beitrag die Bauleitplanung leisten kann, um diese Gesundheitsgefahr zu bewältigen. Schwierigkeiten bereitet zum einen, dass die Gemeinden bei der hierfür zunächst erforderlichen Bestimmung der Luftqualität mit komplexen umweltrechtlichen Vorgaben konfrontiert werden. Zum anderen bestehen Unsicherheiten bei der Bestimmung von Gefahrenschwellen für krebserzeugende Luftschadstoffe. Dieses Zusammenspiel führt zu erheblichen Planungsschwierigkeiten.
Um beantworten zu können, mit welchen Instrumenten und auf welchen Regelungsebenen sich planungsrechtliche Vorgaben zur Minderung von Gesundheitsgefahren durch krebserzeugende Stoffe erreichen lassen, wird zunächst erörtert, dass für krebserzeugende Stoffe belastbare Gefahrenschwellen bestimmbar sind und folglich Grenzwerte festgelegt werden können. Im Anschluss wird auf die Planungsinstrumente des Immissionsschutzrechts sowie des Bodenschutzrechts eingegangen und dargestellt, inwieweit diese es ermöglichen, bestimmbare Gesundheitsgefahren krebserzeugender Stoffe durch entsprechende Vorgaben zu mindern. Schließlich wird untersucht, welchen Beitrag die Bauleitplanung bei der Bewältigung von Gesundheitsgefahren durch krebserzeugende Stoffe leisten kann. Dabei wird auf die Bedeutung gesundheitsschützender Belange bei der Planaufstellung, auf die allgemeinen Voraussetzungen bei der bauleitplanerische Bewältigung von Gesundheitsgefahren durch krebserzeugende Stoffe sowie auf die bauleitplanerischen Instrumente, die zur Verfügung stehen, um vor krebserzeugenden Luftschadstoffen zu schützen, eingegangen. Es werden verschiedene Gestaltungsmöglichkeiten zur Risiko- und Gefahrenvermeidung abstrakt dargestellt sowie vorhandene Beschränkungen aufgezeigt
Unusual properties of the non-cysteinyl coordinated FeS clusters of IscR, YjdI and the Rieske protein
Get PDFIron-sulfur clusters (FeS) are versatile cofactors found in metalloproteins. Most FeS clusters are coordinated exclusively by cysteine residues. However, for an increasing number of proteins the presence of non-cysteinyl coordination has been noted, with a not fully understood role. At least eight other amino acids act as ligands for FeS clusters, with histidine being the first identified and possibly also the most common amino acid to substitute cysteine. Coordination by two histidine residues is found in Rieske and Apd1-like proteins, whereas MitoNEET and presumably also the IscR protein have one histidine ligand. Suggested roles of the histidine residue(s) are tuning of the redox potential, proton-coupled electron transfer (PCET) or modulation of cluster stability.
In this thesis the redox properties of the [2Fe-2S]1+/2+ cluster of Escherichia coli IscR and the pKa values of the histidine ligand in both redox states were investigated to demonstrate that PCET occurs. Combining UV-Vis, CD, EPR, and Mössbauer spectroscopic techniques with redox titrations pKa values of 8.0 and ~11.1 were determined for the histidine ligand in the oxidized and reduced form of IscR, respectively. The redox potentials varied between -49 and -221 mV, at low and high pH values, respectively, with a maximal slope of approximately -55 mV/pH unit between the pK values. Additionally, the impact of these findings on the physiological function in the cellular environment is discussed.
Lack of coordination by a fourth cysteine can lead to cluster instability, as seen in aconitase, which is subject to [4Fe-4S] to [3Fe-4S] cluster conversion. In the second project the YjdI protein from E. coli was characterized. YjdI exhibited g=2.01 and g=12 EPR signals characteristic of a [3Fe-4S]1+/0 cluster but converted to [4Fe-4S]1+ upon reconstitution and reduction. Studies including mutagenesis and Mössbauer spectroscopy will be needed to reveal the fourth cluster ligand of reconstituted YjdI.
PCET has been extensively studied and linked to function in proton translocation for Rieske proteins. For the reduced state of three different Rieske proteins protein film voltammetry indicated that the two pK values are identical and above 12. However, despite EPR spectroscopic characterization of the alkaline (fully deprotonated) species, an intermediate monoprotonated species in the reduced state has not been reported yet. Resorting to a titration between pH 9.5 and 14 of Thermus thermophilus Rieske protein EPR spectroscopy revealed not only the fully protonated and deprotonated species, but also a monoprotonated species with g=2.03, 1.90 and 1.78. Due to the proximity of the pKa values only mixtures of species were found. Strikingly, the system exhibited cooperative behavior: the second pKa (11.8) is lower than the first pKa (12.1).
Overall, these findings deepen the understanding of the redox properties of IscR, contribute to the characterization of YjdI, and demonstrate cooperativity of consecutive ligand deprotonations for the first time in the FeS field. These findings emphasize the need for further research into PCET and properties of FeS proteins