Quantification of Volatile Aldehydes Deriving from In Vitro Lipid Peroxidation in the Breath of Ventilated Patients

Exhaled aliphatic aldehydes were proposed as non-invasive biomarkers to detect increased lipid peroxidation in various diseases. As a prelude to clinical application of the multicapillary column–ion mobility spectrometry for the evaluation of aldehyde exhalation, we, therefore: (1) identified the most abundant volatile aliphatic aldehydes originating from in vitro oxidation of various polyunsaturated fatty acids; (2) evaluated emittance of aldehydes from plastic parts of the breathing circuit; (3) conducted a pilot study for in vivo quantification of exhaled aldehydes in mechanically ventilated patients. Pentanal, hexanal, heptanal, and nonanal were quantifiable in the headspace of oxidizing polyunsaturated fatty acids, with pentanal and hexanal predominating. Plastic parts of the breathing circuit emitted hexanal, octanal, nonanal, and decanal, whereby nonanal and decanal were ubiquitous and pentanal or heptanal not being detected. Only pentanal was quantifiable in breath of mechanically ventilated surgical patients with a mean exhaled concentration of 13 ± 5 ppb. An explorative analysis suggested that pentanal exhalation is associated with mechanical power—a measure for the invasiveness of mechanical ventilation. In conclusion, exhaled pentanal is a promising non-invasive biomarker for lipid peroxidation inducing pathologies, and should be evaluated in future clinical studies, particularly for detection of lung injury.     

Cobalt and Iron Stabilized Ketyl,Ketiminyl and Aldiminyl Radical Anions

Carbonyl and iminyl based radical anions are reactive intermediates in a variety of transformations in organic synthesis. Herein, the isolation of ketyl, and more importantly unprecedented ketiminyl and aldiminyl radical anions coordinated to cobalt and iron complexes is presented. Insights into the electronic structure of these unusual metal bound radical anions is provided by X-Ray diffraction analysis, NMR, IR, UV/Vis and Mössbauer spectroscopy, solid and solution state magnetometry, as well as a by a detailed computational analysis. The metal bound radical anions are very reactive and facilitate the activation of intra- and intermolecular C−H bonds.     

On exponential stability of second order delay differential equations

We propose a new method for studying stability of second order delay differential equations. Results we obtained are of the form: the exponential stability of ordinary differential equation implies the exponential stability of the corresponding delay differential equation if the delays are small enough. We estimate this smallness through the coefficients of this delay equation. Examples demonstrate that our tests of the exponential stability are essentially better than the known ones. This method works not only for autonomous equations but also for equations with variable coefficients and delays.     

Antimicrobial silica particles loaded with quaternary ammonium polyethyleneimine network

Silica particles functionalized with quaternary ammonium groups were prepared by interpenetrating polyethylenimine (PEI) into silica particles and crosslinking with diiodopentane, followed by octyliodide alkylation and methyliodide quaternarization (S‐QA‐PEI). The synthesized S‐QA‐PEI particles were identified with a slight particle size increase of 2–3 µm. Different ratios of PEI:silica particles were prepared and analyzed. While silica particles are negatively charged, ?16.7 ± 5.11 mV, the prepared S‐QA‐PEI particles are positively charged, +50–60 mV. These particles were embedded in poly(ethylene vinyl acetate) and poly(ethylene methacrylic acid) coatings which exhibited strong antibacterial activity. Copyright © 2014 John Wiley & Sons, Ltd.     

Enzymatic Conversion of Flavonoids using Bacterial Chalcone Isomerase and Enoate Reductase

Flavonoids are a large group of plant secondary metabolites with a variety of biological properties and are therefore of interest to many scientists, as they can lead to industrially interesting intermediates. The anaerobic gut bacterium Eubacterium ramulus can catabolize flavonoids, but until now, the pathway has not been experimentally confirmed. In the present work, a chalcone isomerase (CHI) and an enoate reductase (ERED) could be identified through whole genome sequencing and gene motif search. These two enzymes were successfully cloned and expressed in Escherichia coli in their active form, even under aerobic conditions. The catabolic pathway of E. ramulus was confirmed by biotransformations of flavanones into dihydrochalcones. The engineered E. coli strain that expresses both enzymes was used for the conversion of several flavanones, underlining the applicability of this biocatalytic cascade reaction.     

4,4′‐Bipyridine as a Unidirectional Switching Unit for a Molecular Pushing Motor

A chirality switch in which the intrinsic chirality of a 4,4′‐bipyridine is combined with a metal‐ion‐induced switching principle is described. In the uncomplexed state the 4,4′‐bipyridine unit, which is linked to an S,S,S,S‐configured cyclic imidazole peptide, is P‐configured. The addition of zinc ions leads to a rotation around the C?C bond axis of the 4,4′‐bipyridine and the M isomer of the metal complex is formed. By addition of a stronger complexing agent the metal ions are removed and the switch returns to its initial position. The combination of the chirality switch with a second switching unit allows the construction of a molecular pushing motor, which is driven chemically and by light.     

A Tandem In Situ Peptide Cyclization through Trifluoroacetic Acid Cleavage

We present a new approach for peptide cyclization during solid phase synthesis under highly acidic conditions. Our approach involves simultaneous in situ deprotection, cyclization and trifluoroacetic acid (TFA) cleavage of the peptide, which is achieved by forming an amide bond between a lysine side chain and a succinic acid linker at the peptide N‐terminus. The reaction proceeds via a highly active succinimide intermediate, which was isolated and characterized. The structure of a model cyclic peptide was solved by NMR spectroscopy. Theoretical calculations support the proposed mechanism of cyclization. Our new methodology is applicable for the formation of macrocycles in solid‐phase synthesis of peptides and organic molecules.     

Stripping the latex: the challenge of miniemulsion polymerization without initiator,costabilizer and surfactant

When finally processed to provide the function for which the latex was selected―binding, protecting, finishing―components such as surfactant, costabilizer or initiator become generally useless, not to say detrimental. In this study, we show that miniemulsion photopolymerization provides a suitable method to create latex without the apparent addition of these three compounds. Indeed, UV-driven monomer self-initiation can create initiating radicals without the aid of initiator, the fast in situ photogenerated polymer can hinder Ostwald ripening with the assistance of external costabilizer, and finally, UV-transparent clay can replace conventional surfactant to ensure colloidal stabilization. Each strategy has been developed individually before being combined together to end up with a unique miniemulsion procedure free of initiator, costabilizer and surfactant. Such approach paves the way to a simplified and environmentally improved pathway towards aqueous polymer dispersions.     

Back cover: Mn2+ or Mn3+? Investigating transition metal dissolution of manganese species in lithium ion battery electrolytes by capillary electrophoresis

A new CE method with ultraviolet–visible detection was developed in this study to investigate manganese dissolution in lithium ion battery electrolytes. The aqueous running buffer based on diphosphate showed excellent stabilization of labile Mn³⁺, even under electrophoretic conditions. The method was optimized regarding the concentration of diphosphate and modifier to obtain suitable signals for quantification. Additionally, the finally obtained method was applied on carbonate-based electrolytes samples. Dissolution experiments of the cathode material LiNi_0.5Mn_1.5O₄ (lithium nickel manganese oxide [LNMO]) in aqueous diphosphate buffer at defined pH were performed to investigate the effect of a transition metal-ion-scavenger on the oxidation state of dissolved manganese. Quantification of both Mn species revealed the formation of mainly Mn³⁺, which can be attributed to a comproportionation reaction of dissolved and complexed Mn²⁺ with Mn⁴⁺ at the surface of the LNMO structure. It was also shown that the formation of Mn³⁺ increased with lower pH. In contrast, dissolution experiments of LNMO in carbonate-based electrolytes containing LIPF₆ showed only dissolution of Mn²⁺.