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Mouse aldehyde oxidases (mAOXs) have a homodimeric structure and belong to xanthine oxidase family of molybdo-flavoenzymes. In general, each dimer is characterized by three subdomains: a 20 kDa N-terminal 2x[2Fe2S] cluster containing domain, a 40 kDa central FAD-containing domain and an 85 kDa C-terminal molybdenum cofactor (Moco) containing domain. Aldehyde oxidases have a broad substrate specificity including the oxidation of different aldehydes and N-heterocyclic compounds. AOX enzymes are present in mainly all eukaryotes. Four different homologs of AOX were identified to be present with varying numbers among species and rodents like mice and rats contain the highest number of AOX isoenzymes. There are four identified homologs in mouse named mAOX1, mAOX3, mAOX2, and mAOX4. The AOX homologs in mice are expressed in a tissue-specific manner. Expression of mAOX1 and mAOX3 are almost superimposable and predominantly synthesized in liver, lung, and testis. The richest source of mAOX4 is the Harderian gland, which is found within the eye's orbit in tetrapods. Expression of mAOX2 is strictly restricted to the Bowman’s gland, the main secretory organ of the nasal mucosa.
In this study, the four catalytically active mAOX enzymes were expressed in a heterologous expression system in Escherichia coli and purified in a catalytically active form. Thirty different structurally related aromatic, aliphatic and N-heterocyclic compounds were used as substrates, and the kinetic parameters of all four mAOX enzymes were directly compared. The results showed that all enzymes can catalyze a broad range of substrates. Generally, no major differences between mAOX1, mAOX3 and mAOX2 were identified and the substrate specificity of mAOX1, mAOX3, and mAOX2 was broader compared to that of mAOX4 since mAOX4 showed no activity with substrates like methoxy-benzaldehydes, phenanthridine, N1-methyl-nicotinamide, and cinnamaldehyde and 4-(dimethylamino)cinnamaldehyde.
We investigated differences at the flavin site of the mAOX enzymes by measuring the ability of the four mAOX enzymes to oxidize NADH in the absence of oxygen. NADH was able to reduce only mAOX3. The four mouse AOXs are also characterized by quantitative differences in their ability to produce superoxide radicals. mAOX2 is the enzyme generating the largest rate of superoxide radicals of around 40% in relation to moles of substrate converted and it is followed by mAOX1 with a ratio of 30%.
To understand the factors that contribute to the substrate specificity of mAOX4, site-directed mutagenesis was applied to substitute amino acids in the substrate-binding funnel by the ones present in mAOX1, mAOX3, and mAOX2. The amino acids Val1016, Ile1018 and Met1088 were selected as targets. An increase in activity was obtained by the amino acid exchange M1088V in the active site identified to be specific for mAOX4, to the amino acid identified in mAOX3.
The Role of Bargaining Power
(2019)
Neoclassical theory omits the role of bargaining power in the determination of wages. As a result, the importance of changes in the bargaining position for the development of income shares in the last decades is underestimated. This paper presents a theoretical argument why collective bargaining power is a main determinant of workers’ share of income and how its decline contributed to the severe changes in the distribution of income since the 1980s. In order to confirm this hypothesis, a panel data regression analysis is performed that suggests that unions significantly influence the distribution of income in developed countries.
The complete mitochondrial genome of a European fire-bellied toad (Bombina bombina) from Germany
(2019)
The European fire-bellied toad, Bombina bombina, is a small aquatic toad belonging to the family Bombinatoridae. The species is native to the lowlands of Central and Eastern Europe, where population numbers have been in decline in recent past decades. Here, we present the first complete mitochondrial genome of the endangered European fire-bellied toad from Northern Germany recovered using iterative mapping. Phylogenetic analyses including other representatives of the Bombinatoridae placed our German specimen as sister to a Polish B. bombina sequence with high support. This finding is congruent with the postulated Pleistocene history of the species. Our complete mitochondrial genome represents an important resource for further population analysis of the European fire-bellied toad, especially those found within Germany.
The complete mitochondrial genome of a European fire-bellied toad (Bombina bombina) from Germany
(2019)
The European fire-bellied toad, Bombina bombina, is a small aquatic toad belonging to the family Bombinatoridae. The species is native to the lowlands of Central and Eastern Europe, where population numbers have been in decline in recent past decades. Here, we present the first complete mitochondrial genome of the endangered European fire-bellied toad from Northern Germany recovered using iterative mapping. Phylogenetic analyses including other representatives of the Bombinatoridae placed our German specimen as sister to a Polish B. bombina sequence with high support. This finding is congruent with the postulated Pleistocene history of the species. Our complete mitochondrial genome represents an important resource for further population analysis of the European fire-bellied toad, especially those found within Germany.
Background
Semi-natural plant communities such as field boundaries play an important ecological role in agricultural landscapes, e.g., provision of refuge for plant and other species, food web support or habitat connectivity. To prevent undesired effects of herbicide applications on these communities and their structure, the registration and application are regulated by risk assessment schemes in many industrialized countries. Standardized individual-level greenhouse experiments are conducted on a selection of crop and wild plant species to characterize the effects of herbicide loads potentially reaching off-field areas on non-target plants. Uncertainties regarding the protectiveness of such approaches to risk assessment might be addressed by assessment factors that are often under discussion. As an alternative approach, plant community models can be used to predict potential effects on plant communities of interest based on extrapolation of the individual-level effects measured in the standardized greenhouse experiments. In this study, we analyzed the reliability and adequacy of the plant community model IBC-grass (individual-based plant community model for grasslands) by comparing model predictions with empirically measured effects at the plant community level.
Results
We showed that the effects predicted by the model IBC-grass were in accordance with the empirical data. Based on the species-specific dose responses (calculated from empirical effects in monocultures measured 4 weeks after application), the model was able to realistically predict short-term herbicide impacts on communities when compared to empirical data.
Conclusion
The results presented in this study demonstrate an approach how the current standard greenhouse experiments—measuring herbicide impacts on individual-level—can be coupled with the model IBC-grass to estimate effects on plant community level. In this way, it can be used as a tool in ecological risk assessment.
Textbook concepts of diffusion-versus kinetic-control are well-defined for reaction-kinetics involving macroscopic concentrations of diffusive reactants that are adequately described by rate-constants—the inverse of the mean-first-passage-time to the reaction-event. In contradiction, an open important question is whether the mean-first-passage-time alone is a sufficient measure for biochemical reactions that involve nanomolar reactant concentrations. Here, using a simple yet generic, exactly solvable model we study the effect of diffusion and chemical reaction-limitations on the full reaction-time distribution. We show that it has a complex structure with four distinct regimes delineated by three characteristic time scales spanning a window of several decades. Consequently, the reaction-times are defocused: no unique time-scale characterises the reaction-process, diffusion- and kinetic-control can no longer be disentangled, and it is imperative to know the full reaction-time distribution. We introduce the concepts of geometry- and reaction-control, and also quantify each regime by calculating the corresponding reaction depth.
Abstract
The emerging diffusive dynamics in many complex systems show a characteristic crossover behaviour from anomalous to normal diffusion which is otherwise fitted by two independent power-laws. A prominent example for a subdiffusive–diffusive crossover are viscoelastic systems such as lipid bilayer membranes, while superdiffusive–diffusive crossovers occur in systems of actively moving biological cells. We here consider the general dynamics of a stochastic particle driven by so-called tempered fractional Gaussian noise, that is noise with Gaussian amplitude and power-law correlations, which are cut off at some mesoscopic time scale. Concretely we consider such noise with built-in exponential or power-law tempering, driving an overdamped Langevin equation (fractional Brownian motion) and fractional Langevin equation motion. We derive explicit expressions for the mean squared displacement and correlation functions, including different shapes of the crossover behaviour depending on the concrete tempering, and discuss the physical meaning of the tempering. In the case of power-law tempering we also find a crossover behaviour from faster to slower superdiffusion and slower to faster subdiffusion. As a direct application of our model we demonstrate that the obtained dynamics quantitatively describes the subdiffusion–diffusion and subdiffusion–subdiffusion crossover in lipid bilayer systems. We also show that a model of tempered fractional Brownian motion recently proposed by Sabzikar and Meerschaert leads to physically very different behaviour with a seemingly paradoxical ballistic long time scaling.
Die Verwandlung
(2019)