A Toxoplasma gondii Oxopurine Transporter Binds Nucleobases and Nucleosides Using Different Binding Modes

Toxoplasma gondii is unable to synthesize purines de novo, instead salvages them from its environment, inside the host cell, for which they need high affinity carriers. Here, we report the expression of a T. gondii Equilibrative Nucleoside Transporter, Tg244440, in a Trypanosoma brucei strain from which nucleobase transporters have been deleted. Tg244440 transported hypoxanthine and guanine with similar affinity (K_m ~1 µM), while inosine and guanosine displayed K_i values of 4.05 and 3.30 µM, respectively. Low affinity was observed for adenosine, adenine, and pyrimidines, classifying Tg244440 as a high affinity oxopurine transporter. Purine analogues were used to probe the substrate-transporter binding interactions, culminating in quantitative models showing different binding modes for oxopurine bases, oxopurine nucleosides, and adenosine. Hypoxanthine and guanine interacted through protonated N1 and N9, and through unprotonated N3 and N7 of the purine ring, whereas inosine and guanosine mostly employed the ribose hydroxy groups for binding, in addition to N1H of the nucleobase. Conversely, the ribose moiety of adenosine barely made any contribution to binding. Tg244440 is the first gene identified to encode a high affinity oxopurine transporter in T. gondii and, to the best of our knowledge, the first purine transporter to employ different binding modes for nucleosides and nucleobases.     

Quantenchemische Untersuchungen zur Molekül- und Elektronenstruktur einfacher Azomethinimine und verwandter Verbindungen

Quantum Chemical Investigations of the Molecular and Electronic Structure of Simple Azomethine Imines and Related Compounds The molecular and electronic structure of simple azomethinimines are investigated by means of MINDO/3 and CNDO/2 calculations. The calculated molecular geometry is compared with X-ray results obtained for these compounds. Except for the NN-bond lengths MINDO/3 satisfactorily describes the molecular structure of azomethinimine and related π-electronic systems. The charges at the atoms along the conjugated chain are alternating as in polymethines. The terminal carbon atom carries a negative charge. This charge brings about an appreciable shielding of this carbon atom such as found in the ¹³C-n.m.r. spectrum. This result does not contradict a stabilization of azomethinimines in the crystal via = CH…︁OC interactions.     

Effect of load reduction mechanisms on loads and blade bearing movements of wind turbines

The power control of wind turbines is usually realized via a change in the pitch angle of the rotor blades. Pitching facilitates the exact control of the turbines and the reliable deceleration of the rotor when required. Pitch movements can moreover be used for load control. One of these methods is called individual pitch control (IPC). IPC controls the blades individually and brings about a significant reduction in the fatigue loads and extreme loads placed on the structural components, while at the same time reducing the yield of the turbine only slightly. The lower loads reduce material costs, and thus, the cost of energy (CoE) is reduced, despite the slight reduction in yield. The method is nevertheless not used everywhere since the additional movement cycles put the rotor blade bearings in particular under stress. Special attention must be paid to small amplitude oscillating movements, which carry a high risk of inducing surface damage in the rolling contacts of the blade bearings. This paper uses a cycle analysis of the IWT7.5‐164 reference turbine to illustrate the differences in the movement patterns of wind turbine blade bearings with and without IPC. Moreover, model calculations with single contacts are used to show which of the movement patterns carries a risk of inducing surface damage. The use of IPC leads to the expected load reduction at the blade root. In current literature, IPC is usually assumed to have a negative influence on the life expectancy of blade bearings, but the findings of this study contradict this. The summed blade bearing movement is increased, although the number of very small pitch angles occurring is reduced. This reduction reduces the risk of wear in the blade bearings.     

Context-Based Path Prediction for Targets with Switching Dynamics

International Journal of Computer Vision - Anticipating future situations from streaming sensor data is a key perception challenge for mobile robotics and automated vehicles. We address the problem...     

Disruption of cellular translational control by a viral truncated eukaryotic translation initiation factor 2alpha kinase homolog

Phosphorylation of eukaryotic translation initiation factor 2alpha (eIF2alpha) is a common cellular mechanism to limit protein synthesis in stress conditions. Baculovirus PK2, which resembles the C-terminal half of a protein kinase domain, was found to inhibit both human and yeast eIF2alpha kinases. Insect cells infected with wild-type, but not pk2-deleted, baculovirus exhibited reduced eIF2alpha phosphorylation and increased translational activity. The negative regulatory effect of human protein kinase RNA-regulated (PKR), an eIF2alpha kinase, on virus production was counteracted by PK2, indicating that baculoviruses have evolved a unique strategy for disrupting a host stress response. PK2 was found in complex with PKR and blocked kinase autophosphorylation in vivo, suggesting a mechanism of kinase inhibition mediated by interaction between truncated and intact kinase domains.     

Surface chemistry of phosphorus-containing carbons of lignocellulosic origin

Activated carbon adsorbents were prepared by phosphoric acid activation of fruit stones in an argon atmosphere at various temperatures in the 400-1000 °C range and at different acid/precursor impregnation ratios (0.63-1.02). The surface chemistry of the carbons was investigated by elemental analysis, cation exchange capacity (CEC, measured by neutralization of NaOH with acidic surface groups), infrared spectroscopy and potentiometric titration. Porous structure was derived from adsorption isotherms (N₂ at −196 °C and CO₂ at 0 °C). It was demonstrated that all carbons show considerable cation exchange capacity, the maximum (CEC = 2.2 mmol g⁻¹) being attained at 800 °C, which coincides with the maximum contents of phosphorus and oxygen. The cation exchange properties of phosphoric acid activated carbons from fruit stones are chemically stable in very acidic and basic solutions. Proton affinity distributions of all carbons show the presence of three types of surface groups with pK at 2.0-3.3, 4.6-5.9 and 7.6-9.1. These pK ranges were ascribed primarily to: (a) phosphorus-containing and carboxylic groups; (b) lactonic groups, and (c) phenolic groups, respectively. Phosphoric acid activated carbons are microporous with a relatively small contribution of mesopores. A maximum BET surface area of 1740 m² g⁻¹ was attained at 400 °C.     

Thiol-ene emulsion polymerization using a semi-continuous approach

The thermally initiated thiol-ene emulsion polymerization of diallyl phthalate (DAP) diene and ethylenedioxy diethanthiol (EDDT) dithiol monomers in batch and semibatch emulsion polymerization is investigated. The batch process leads to larger and broader particle sizes than when the polymerization is carried out in semibatch. The evolution of the particle size and the final particle size distribution indicate that the stability of the latexes is limited and, hence, aggregation phenomena occurred in both processes. In particular, the evolution of the particle size distribution (PSD) in the semibatch process indicates nucleation, growth, and aggregation occurring simultaneously that produced a bimodal particle size. When the diene monomer was changed to diallyl terephthalate (DATP), the semibatch polymerization yielded smaller particles and narrow distribution without any indication of aggregation. The partial substitution of the dithiol by a trithiol monomer that is substantially more water insoluble affected nucleation of the particles, yielding for both systems smaller particles. The polythioether polymers synthesized present low glass transition temperatures (~ −30/−40°C) and those containing the therephthalate yield crystalline films. The potential application of the polymers as pressure sensitive adhesives (PSAs) was preliminarily assessed.     

Asymmetric Synthesis of 3‐Substituted Cyclohexylamine Derivatives from Prochiral Diketones via Three Biocatalytic Steps

Prochiral bicyclic diketones were transformed to a single diastereomer of 3‐substituted cyclohexylamine derivatives via three consecutive biocatalytic steps. The two chiral centres were set up by a C C hydrolase (6‐oxocamphor hydrolase) in the first step and by an ω‐transaminase in the last step. The esterification of the intermediate keto acid was catalysed by a lipase in the second step if possible. For two substrates the C C hydrolytic step as well as the esterification could be run simultaneously in a one‐pot cascade in an organic solvent. In one example, the reaction mixture of the first two steps could be directly subjected to bio‐amination in an organic solvent without the need to change the reaction medium. Depending on the choice of the ω‐transaminase employed and the substrate the cis‐ as well as the trans‐diastereomers could be obtained in optically pure forms.