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.     

Recoil-proton polarization in high-energy deuteron photodisintegration with circularly polarized photons

We measured the angular dependence of the three recoil-proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily. Transverse polarizations are not well described, but suggest isovector dominance.     

Methane dissociation on Ni(111): the role of lattice reconstruction

The effects of lattice motion and reconstruction on the dissociation of methane on Ni(111) are explored, using both electronic structure theory and quantum dynamical calculations. We show that during the reaction, the Ni lattice reconstructs, effectively lowering the barrier to reaction, in contrast with earlier models of this process.     

Binary diffractive beam splitters with arbitrary diffraction angles

Diffractive optical beam splitters designed with iterative Fourier transform type algorithms can produce only certain diffraction angles given by the spatial frequencies used for the computations, which are multiples of a certain base spatial frequency. We have developed a design algorithm that overcomes this limitation and can be used to compute binary diffractive elements with arbitrary diffraction angles. The simulated and experimentally measured properties of optical elements producing beam arrays in circular arrangements are presented and discussed.     

Soluble Congeners of Prior Insoluble Shape-Persistent Imine Cages

One of the most applied reaction types to synthesize shape-persistent organic cage compounds is the imine condensation reaction and it is assumed that the formed cages are thermodynamically controlled products due to the reversibility of the imine condensation. However, most of the synthesized imine cages reported are formed as precipitate from the reaction mixture and therefore rather may be kinetically controlled products. There are even examples in literature, where resulting cages are not soluble at all in common organic solvents to characterize or study their formation by NMR spectroscopy in solution. Here, a triptycene triamine containing three solubilizing n-hexyloxy chains has been used to synthesize soluble congeners of prior insoluble cages. This allowed us to study the formation as well as the reversibility of cage formation in solution by investigating exchange of building blocks between the cages and deuterated derivatives thereof.     

A Molecular Photosensitizer in a Porous Block Copolymer Matrix-Implications for the Design of Photocatalytically Active Membranes

Recently, porous photocatalytically active block copolymer membranes were introduced, based on heterogenized molecular catalysts. Here, we report the integration of the photosensitizer, i. e., the light absorbing unit in an intermolecular photocatalytic system into block copolymer membranes in a covalent manner. We study the resulting structure and evaluate the orientational mobility of the photosensitizer as integral part of the photocatalytic system in such membranes. To this end we utilize transient absorption anisotropy, highlighting the temporal reorientation of the transition dipole moment probed in a femtosecond pump-probe experiment. Our findings indicate that the photosensitizer is rigidly bound to the polymer membrane and shows a large heterogeneity of absolute anisotropy values as a function of location probed within the matrix. This reflects the sample inhomogeneity arising from different protonation states of the photosensitizer and different intermolecular interactions of the photosensitizers within the block copolymer membrane scaffold.     

Switching the Mechanism of NADH Photooxidation by Supramolecular Interactions

A series of three Ru(II) polypyridine complexes was investigated for the selective photocatalytic oxidation of NAD(P)H to NAD(P)⁺ in water. A combination of (time-resolved) spectroscopic studies and photocatalysis experiments revealed that ligand design can be used to control the mechanism of the photooxidation: For prototypical Ru(II) complexes a ¹O₂ pathway was found. Rudppz ([(tbbpy)₂Ru(dppz)]Cl₂, tbbpy=4,4'-di-tert-butyl-2,2'-bipyridine, dppz=dipyrido[3,2-a:2′,3′-c]phenazine), instead, initiated the cofactor oxidation by electron transfer from NAD(P)H enabled by supramolecular binding between substrate and catalyst. Expulsion of the photoproduct NAD(P)⁺ from the supramolecular binding site in Rudppz allowed very efficient turnover. Therefore, Rudppz permits repetitive selective assembly and oxidative conversion of reduced naturally occurring nicotinamides by recognizing the redox state of the cofactor under formation of H₂O₂ as additional product. This photocatalytic process can fuel discontinuous photobiocatalysis.     

A semiclassical adiabatic calculation of state densities for molecules exhibiting torsion: application to hydrogen peroxide and its isotopomers

A practical computational method is discussed for obtaining the rotational–vibrational molecular state densities of molecules with large amplitude torsional degrees of freedom (DoFs). This method goes beyond the traditional harmonic oscillator/rigid rotor or separable hindered rotor approximations in that it includes coupling between the torsion, the remaining vibrational modes, and the overall rotation. The method is based on the vibrationally adiabatic approximation whereby the torsional motion is assumed to be slow compared to the remaining vibrational DoFs although the nonseparability may be large. The torsional coordinate therefore parameterizes the rotational constants and the effective vibrational potential. A semiclassical method is then introduced to calculate the total state density in which the torsion is treated classically while the remaining coordinates are treated quantum mechanically. The method is also formulated for reactive problems in which the density of states is parameterized by a second large amplitude degree of freedom, the reaction coordinate. The performance of the method is assessed using the dissociation reaction of the hydrogen peroxide molecule and its isotopomers. It is found that the method performs well based on numerical tests. The torsional nonseparability is found to yield errors of factors of 2–3 in the statistical rate coefficient when compared with results of traditional separable models.     

Photostability of 4,4′‐Dihydroxythioindigo,a Mimetic of Indigo

The photochemical properties of indigo, a widely used industrial dye, has attracted both experimentalists and theoreticians from the beginning. Especially the high photostability of indigo has been the subject of intensive research. Recently, it was proposed that after photoexcitation an intramolecular proton transfer followed by a nonradiative relaxation to the ground state promote photostability. In indigo the hydrogen bond and the proton transfer occur between the opposing hemiindigo parts. Here, we provide experimental and theoretical evidence that a hydrogen transfer within one hemiindigo or hemithioindigo part is sufficient to attain photostability. This concept can serve as an interesting strategy towards new photostable dyes for the visible part of the spectrum.     

Electrochemically Generated Gradients

This review surveys recent developments in the field of electrochemically generated gradients. The gradual variation of properties, which is a key characteristic of gradients, is of eminent importance in technology, for example, directional wetting, as well as biology, for example, chemotaxis. Electrochemical techniques offer many benefits, such as the generation of dynamic solution and surface gradients, integration with electronics, and compatibility with automation. An overview is given of newly developed methods, from purely electrochemical techniques to the combination of electrochemistry with other methods. Electrochemically fabricated gradients are employed extensively for biological and technological applications, such as high‐throughput screening, high‐throughput deposition, and device development, all of which are covered herein. Especially promising are developments towards the study and control of dynamic phenomena, such as the directional motion of molecules, droplets, and cells.