Towards Heterogeneous and Green Versions of Os Dihydroxylation Catalysis

Os-catalyzed dihydroxylation will find more widespread application if truly heterogeneous catalysts are available which use O₂ or H₂O₂ as terminal oxidants. This paper discusses and critically evaluates the concepts by which Os can be anchored on solid supports. New methods are also available for reoxidation of hexavalent to octavalent Os.     

Aphid deterrence by glucose esters in glandular trichome exudate of the wild tomato,Lycopersicon pennellii

Settling of the potato aphid,Macrosiphum euphorbiae, on feeding membranes was deterred by methanolic leaf rinses ofLycopersicon pennellii, or of its F₁ with tomato,L. esculentum. The active compounds in theL. pennellii rinsates were identified as 2,3,4-tri-O-acylglucoses bearing short to medium chain length fatty acids. These compounds are localized in the glandular exudate of the type IV trichomes and may accumulate to levels in excess of 400 g/cm². In choice assays, purified glucose esters fromL. pennellii reduced aphid settling at concentrations as low as 25 g/cm²; at concentrations of 150 g/cm² or more, all aphids avoided treated areas. Glucose esters were also active in deterring aphid settling in no-choice assays. At 100 g/ cm², these esters resulted in increased levels of mortality after 48 hr.     

Rethinking the Citric Acid Cycle: Connecting Pyruvate Carboxylase and Citrate Synthase to the Flow of Energy and Material

In 1937, Sir H. A Krebs first published the Citric Acid Cycle, a unidirectional cycle with carboxylic acids. The original concept of the Citric Acid Cycle from Krebs’ 1953 Nobel Prize lecture illustrates the unidirectional degradation of lactic acid to water, carbon dioxide and hydrogen. Here, we add the heart lactate dehydrogenase•proton-linked monocarboxylate transporter 1 complex, connecting the original Citric Acid Cycle to the flow of energy and material. The heart lactate dehydrogenase•proton-linked monocarboxylate transporter 1 complex catalyses the first reaction of the Citric Acid Cycle, the oxidation of lactate to pyruvate, and thus secures the provision of pyruvic acid. In addition, we modify Krebs’ original concept by feeding the cycle with oxaloacetic acid. Our concept enables the integration of anabolic processes and allows adaption of the organism to recover ATP faster.     

Release of reduced inorganic selenium species into waters by the green fresh water algae Chlorella vulgaris

The common green fresh water algae Chlorella vulgaris was exposed to starting concentrations of 10 μg/L selenium in the form of selenate, selenite, or selenocyanate (SeCN(-)) for nine days in 10% Bold's basal medium. Uptake of selenate was more pronounced than that of selenite, and there was very little uptake of selenocyanate. Upon uptake of selenate, significant quantities of selenite and selenocyanate were produced by the algae and released back into the growth medium; no selenocyanate was released after selenite uptake. Release of the reduced metabolites after selenate exposure appeared to coincide with increasing esterase activity in solution, indicating that cell death (lysis) was the primary emission pathway. This is the first observation of biotic formation of selenocyanate and its release into waters from a nonindustrial source. The potential environmental implications of this laboratory observation are discussed with respect to the fate of selenium in impacted aquatic systems, the ecotoxicology of selenium bioaccumulation, and the interpretation of environmental selenium speciation data generated, using methods incapable of positively identifying reduced inorganic selenium species, such as selenocyanate.     

Asymmetric synthesis and conformational analysis by NMR spectroscopy and MD of Aba- and α-MeAba-containing dermorphin analogues

Dermorphin analogues, containing a (S)‐ and (R)‐4‐amino‐1,2,4,5‐tetrahydro‐2‐benzazepin‐3‐one scaffold (Aba) and the α‐methylated analogues as conformationally constrained phenylalanines, were prepared. Asymmetric phase‐transfer catalysis was unable to provide the (S)‐α‐Me‐o‐cyanophenylalanine precursor for (S)‐α‐MeAba in acceptable enantiomeric purity. However, by using a Schöllkopf chiral auxiliary, this intermediate was obtained in 88 % ee. [(S)‐Aba 3‐Gly 4]dermorphin retained μ‐opioid affinity but displayed an increased δ‐affinity. The corresponding R epimer was considerably less potent. In contrast, the [(R)‐α‐MeAba 3‐Gly 4]dermorphin isomer was more potent than its S epimer. Tar‐MD simulations of both non‐methylated [Aba 3‐Gly 4]dermorphin analogues showed a degree of folding at the C‐terminal residues toward the N terminus of the peptide, without however, adopting a stabilized β‐turn conformation. The α‐methylated analogues, on the other hand, exhibited a type I/I′ β‐turn conformation over the α‐MeAba 3 and Gly 4 residues, which was stabilized by a hydrogen bond involving Tyr 5‐H_N and D ‐Ala 2‐CO.     

Improving the thickness accuracy of cold rolled narrow strip by piezoelectric roll gap control at high rolling speed

Particularly in fast rolling mills, conventional actuators reach their dynamic limits, when longitudinal thickness variations of the incoming strip shall be reduced with high accuracy by model-predictive roll gap control. Accordingly, the applicability of highly dynamic piezoelectric actuators in combination with electromechanical spindles and a high frequency precision measurement of the thickness in front of the roll gap was examined. Rolling tests in a cold rolling mill for narrow slit strips show that this novel concept is suitable to provide the required dynamic actuation especially at high rolling speed.     

A new ternary phase in the system CaO–Al2O3–Cr2O3: Crystal structure and thermal expansion of CaAl2Cr2O7

Polycrystalline material of a novel phase in the system CaO–Al₂O₃–Cr₂O₃ has been obtained by solid-state reactions. Chemical analysis indicated the composition CaAl₂Cr₂O₇. Single-crystal growth of the new compound using borax as a mineralizer was successful. Diffraction experiments at ambient conditions on a crystal with composition CaAl_2.13Cr_1.87O₇ yielded the following basic crystallographic data: space group P 3, a = 7.7690(5) Å, c = 7.6463(5) Å, V = 399.68(6) ų, Z = 3. Structure determination and subsequent least-squares refinements resulted in a residual of R(|F|) = 2.3% for 1440 independent observed reflections and 113 parameters. To the best of our knowledge, the structure of CaAl_2.13Cr_1.87O₇ or CaAl₂Cr₂O₇ represents a new structure type. It belongs to the group of double layer structures where individual double layers contain octahedrally and tetrahedrally coordinated cation positions. Linkage between neighboring sheet packages is provided by additional calcium cations. Furthermore, thermal expansion has been studied in the interval between 29 and 790°C using in situ high-temperature single-crystal diffraction. No indications for a structural phase transition were observed. From the evolution of the lattice parameters the thermal expansion tensor has been obtained. A pronounced anisotropy is evident. The response of structural building units to variable temperature has been discussed.     

Indoloazepinone‐Constrained Oligomers as Cell‐Penetrating and Blood–Brain‐Barrier‐Permeating Compounds

Non‐cationic and amphipathic indoloazepinone‐constrained (Aia) oligomers have been synthesized as new vectors for intracellular delivery. The conformational preferences of the [l ‐Aia‐Xxx]_n oligomers were investigated by circular dichroism (CD) and NMR spectroscopy. Whereas Boc‐[l ‐Aia‐Gly]_2,4‐OBn oligomers 12 and 13 and Boc‐[l ‐Aia‐β³‐h‐l ‐Ala]_2,4‐OBn oligomers 16 and 17 were totally or partially disordered, Boc‐[l ‐Aia‐l ‐Ala]₂‐OBn ( 14 ) induced a typical turn stabilized by C₅‐ and C₇‐membered H‐bond pseudo‐cycles and aromatic interactions. Boc‐[l ‐Aia‐l ‐Ala]₄‐OBn ( 15 ) exhibited a unique structure with remarkable T‐shaped π‐stacking interactions involving the indole rings of the four l ‐Aia residues forming a dense hydrophobic cluster. All of the proposed FITC‐6‐Ahx‐[l ‐Aia‐Xxx]₄‐NH₂ oligomers 19 – 23 , with the exception of FITC‐6‐Ahx‐[l ‐Aia‐Gly]₄‐NH₂ ( 18 ), were internalized by MDA‐MB‐231 cells with higher efficiency than the positive references penetratin and Arg₈. In parallel, the compounds of this series were successfully explored in an in vitro blood–brain barrier (BBB) permeation assay. Although no passive diffusion permeability was observed for any of the tested Ac‐[l ‐Aia‐Xxx]₄‐NH₂ oligomers in the PAMPA model, Ac‐[l ‐Aia‐l ‐Arg]₄‐NH₂ ( 26 ) showed significant permeation in the in vitro cell‐based human model of the BBB, suggesting an active mechanism of cell penetration.     

SkaSim – Skalierbare HPC‐Software für molekulare Simulationen in der chemischen Industrie

This article outlines advances in molecular modeling and simulation using massively parallel high‐performance computers (HPC). In the SkaSim project, partners from the HPC community collaborated with users from science and industry. The aim was to optimize the prediction of thermodynamic property data in terms of efficiency, quality and reliability using HPC methods. In this context, various topics were dealt with: atomistic simulation of homogeneous gas bubble formation, surface tension of classical fluids and ionic liquids, multicriteria optimization of molecular models, the development of the molecular simulation codes ls1 mardyn and ms2, atomistic simulation of gas separation processes, molecular membrane structure generators, transport resistors and the evaluation of predictive property data models based on specific mixture types.     

Imidazolium-substituted ionic (co)polythiophenes: Compositional influence on solution behavior and thermal properties

A series of ionic polythiophenes, in homopolymer and random copolymer configurations, is prepared via the Grignard metathesis (GRIM) polymerization protocol and subsequent substitution on the bromohexyl side chains with N-methylimidazole. The introduced structural variations – comonomer ratio, side chain composition, counter ions – allow tuning of the thermal properties and solution behavior of the resulting conjugated polymers. As expected, the solubility depends majorly on the number of ionic groups and the counter ions. The most peculiar behavior is observed for the P3HT-P3(MIM)HT-Br 50/50 random copolymer, which shows organization of the polymer chains in solution and thin film dependent on the preparation conditions. Dynamic light scattering studies confirm that the ordered solid-state structure is somewhat maintained when the copolymer is dissolved in a bad solvent mixture. The ionic (co)polythiophenes are generally more resistant to thermal degradation than their precursors. The precursor polymers all show a clear semi-crystalline behavior, with a decrease in crystallinity upon decreasing the number of regular 3-hexylthiophene units. On the other hand, the studied ionic (co)polythiophenes are fully amorphous. Changes in the counter ions have dramatic effects on the thermal properties. Bromine counter ions render the polymers strongly hygroscopic. The novel materials are of particular appeal in the field of organic photovoltaics, in which the imidazolium-substituted (co)polythiophenes can be beneficially applied as constituents of either active layers or electron transport layers. Their processability from green solvents is also of major importance for the field.