Possibilities and limitations of the photoelectric aerosol sensor array applied to heavy metal aerosols

Summary The technique of substance-selective aerosol charging by photoelectron emission was applied to several ultrafine heavy metal aerosols. To enhance the selectivity of the Photoelectric Aerosol Sensor (PAS), an array operating with four different wavelengths (185 nm, 214 nm, 229 nm, 254 nm) was used. The photoelectric activity at each wave-length and the linearity of the PAS signal was investigated for monodisperse and quasi-polydisperse systems. The aerosol mass concentration was determined by correlation with atomic absorption spectroscopy measurements of filter samples. Pattern recognition was applied to differentiate between four different aerosol systems and to identify common interferences.

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Möglichkeiten und Grenzen des photoelektrischen Aerosolsensors für die Analyse von Schwermetallaerosolen

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Dedicated to Prof. Dr. G. Tölg on the occasion of his 60th birthday     

Electron correlation effects in cobalt fluorides CoFn

The molecular cobalt fluorides CoF₂, CoF₃ and CoF₄ are studied and compared by employing different basis sets as well as Quantum Information Theory (QIT) to investigate their correlation effects. These prototypical monomers may be systematically extended in size yielding a novel quasi 1-dimensional, strongly correlated model system consisting of cobalt atoms bridged by oxygen atoms and fluorine termination on both ends. Accurate correlation energies are obtained using Full Configuration Interaction (FCI) and Full Configuration Interaction Quantum Monte Carlo (FCIQMC) calculations and the results are compared to Coupled Cluster and Density Matrix Renormalization Group (DMRG) energies. The analysis indicates the cobalt atom requires a larger number of one-electron basis functions than fluorine and the use of localized molecular orbitals may facilitate calculations for the extended systems.     

Inter- and Intramolecular Aryl–Aryl Interactions in Partially Fluorinated Ethylenedioxy-bridged Bisarenes**

Several ethylenedioxy-bridged bisarenes with a variety of type and number of aryl groups were synthesized to study non-covalent dispersion-driven inter- and intramolecular aryl–aryl interactions in the solid state and gas phase. Intramolecular interactions are preferably found in the gas phase. DFT calculations with and without dispersion correction show larger interacting aromatic groups increase the stabilization energy of folded conformers and decrease the intermolecular centroid–centroid distance. Single-molecule structures generally adopt folded conformations with short intramolecular aryl–aryl contacts. Gas electron diffraction experiments were performed exemplarily for 1-(pentafluorophenoxy)-2-(phenoxy)ethane. A new procedure for structure refinement was developed to deal with the conformational complexity of such molecules. The results are an experimental confirmation of the existence of folded conformations of this molecule with short intramolecular aryl–aryl distances in the gas phase. Solid-state structures are dominated by stretched structures without intramolecular aryl–aryl interactions but interactions with neighboring molecules.     

Design and characterization of endosomal-pH-responsive coiled coils for constructing an artificial membrane fusion system

A weakly acidic pH-responsive polypeptide is believed to have the potential for an endosome escape function in a polypeptide-triggered delivery system. For constructing a membrane fusion device with pH-responsiveness, we have designed novel polypeptides that are capable of forming an α2 coiled coil structure. Circular dichroism spectroscopy reveals that a polypeptide, AP-LZ(EH5), with a Glu and His salt-bridge pair at a staggered position in the hydrophobic core forms a stable coiled coil structure only at endosomal pH values (pH 5.0 to 5.5). On the basis of their endosomal-pH responsiveness, a boronic acid/polypeptide conjugate (BA-H5-St) was also designed as a pilot molecule to construct a pH-responsive, one-way membrane fusion system with a sugarlike compound (phosphatidylinositol: PI)-containing liposome as a target. Membrane fusion behavior was characterized by lipid-mixing, inner-leaflet lipid-mixing, and contents-mixing assays. These studies reveal that membrane fusion is clearly observed when the pH of the experimental system is changed from 7.4 (physiological condition) to 5.0 (endosomal condition).     

Mass spectrometry and inflammation—MS methods to study oxidation and enzyme-induced changes of phospholipids

Many diseases such as arthritis or atherosclerosis are accompanied by inflammatory processes. Inflammation is characterized by the infiltration of cells such as neutrophilic granulocytes and (a) the release of phospholipases [particularly phospholipase A₂ (PLA₂)] and (b) the generation of reactive oxygen as well as nitrogen species (ROS and RNS). While PLA₂ leads to defined lyso products (lacking one acyl residue), lipid oxidation is characterized by much more complex product patterns, including lipid peroxides, aldehydes (by double bond cleavage), and many others. Nevertheless, oxidation processes are highly important under in vivo conditions because molecules with regulatory functions are generated by the oxidation of lipids and/or free fatty acids. Therefore, lipid oxidation products as well as lysolipids are increasingly assumed to represent important disease (bio)markers. Consequently, there is also increasing interest in methods to characterize these products qualitatively and quantitatively. Mass spectrometry (MS) seems to be the method of choice to study (phospho)lipids changed under inflammatory conditions: nowadays, soft ionization MS methods are regularly used to study oxidative lipid modifications because of their high sensitivities and the tremendous mass resolutions that are achievable by using modern mass spectrometers. However, experimental care is required to be able to detect all relevant products. Although electrospray ionization (ESI) MS is so far most popular, applications of matrix-assisted laser desorption and ionization (MALDI) MS are continuously increasing. This review aims to summarize the so far available data on MS analyses of oxidized lipids as well as lysolipids. In addition to model systems, special attention will be paid to the monitoring of oxidized lipids and lysolipids under in vivo conditions. It is the aim of this review to provide a critical survey of the advantages and drawbacks of the different MS methods, with the focus on MALDI and ESI.

Diaminodicyanoquinones: Fluorescent Dyes with High Dipole Moments and Electron‐Acceptor Properties

Fluorescent dyes are applied in various fields of research, including solar cells and light‐emitting devices, and as reporters for assays and bioimaging studies. Fluorescent dyes with an added high dipole moment pave the way to nonlinear optics and polarity sensitivity. Redox activity makes it possible to switch the molecule's photophysical properties. Diaminodicyanoquinone derivatives possess high dipole moments, yet only low fluorescence quantum yields, and have therefore been neglected as fluorescent dyes. Here we investigate the fluorescence properties of diaminodicyanoquinones using a combined theoretical and experimental approach and derive molecules with a fluorescence quantum yield exceeding 90 %. The diaminodicyanoquinone core moiety provides chemical versatility and can be integrated into novel molecular architectures with unique photophysical features.     

Stereoselective Epoxidation of Cyclohexa-Anellated Triquinacenes with Iodine/Silver(I) Oxide As Compared to m-Chloroperbenzoic Acid(1)

Iodine/silver(I) oxide (I(2)/Ag(2)O) reacts highly stereoselectively in the single, double, and triple anti epoxidation of the spherical 1,4,7-triene, 10-methyl-2,3:5,6:8,9-tris(cyclohexano)triquinacene 1. All of the three epoxides 3, 4, and 5 obtained with this reagent contain the epoxy groups at the convex side of the triquinacene framework. The stereochemical course of the epoxidation with I(2)/Ag(2)O is clearly distinct from that observed with m-chloroperbenzoic acid (MCPBA), which gives the same monoepoxide (3) but exclusively anti,syn di- and triepoxides (6-8) bearing at least one epoxy group at the concave side of the triquinacene framework. Epoxidation of the related three-fold 1,4-cyclohexadiene, tris(cyclohexeno)triquinacene 2, with MCPBA occurs similarly to the conversion of 1, whereas I(2)/Ag(2)O reacts with high regioselectivity at the less electron-rich peripheral double bonds of 2 giving triepoxides 12 and 13. The molecular structure of triepoxide 8 has been elucidated in detail by X-ray crystal structure analysis.     

A simple method to identify ether lipids in spermatozoa samples by MALDI-TOF mass spectrometry

Plasmalogens (alkenylacyl glycerophospholipids) are important lipid constituents of many tissues and cells (e.g., selected spermatozoa). Since the molecular weights of plasmalogens overlap with that of diacyl- or alkyl acyl lipids, sophisticated mass spectrometry (MS; including MS/MS) analysis is normally used for the unequivocal identification of plasmalogens. We will show here that a simple matrix-assisted laser desorption/ionization time-of-flight mass spectrometer (without MS/MS capability) in combination with acidic hydrolysis and subsequent derivatization with 2,4-dinitrophenylhydrazine (DNPH) and/or digestion with phospholipase A₂ (PLA₂) is sufficient to determine the contributions of ether lipids in spermatozoa extracts. As neither diacyl nor alkylacyl lipids are sensitive to acids and do not react with DNPH, the comparison of the mass spectra before and after treatment with acids and/or DNPH addition readily provides unequivocal information about the plasmalogen content. Additionally, the released aldehydes are readily converted into the 2,4-dinitrophenylhydrazones and can be easily identified in the corresponding negative ion mass spectra. Finally, PLA₂ digestion is very useful in confirming the presence of plasmalogens. The suggested method was validated by analyzing roe deer, bovine, boar, and domestic cat spermatozoa extracts and comparing the results with isolated phospholipids.

Identification and quantification of cotton-bound,cyclic polycarboxylic acids by means of isocratic HPLC

Cotton fabrics are modified by means of polycarboxylic acids (PCA) in combination with an inorganic catalyst in order to impart durable press properties. To evaluate the effectiveness of cyclic PCA, 100% cotton fabrics were treated with 1,2,3,4,5,6-cyclohexanehexacarboxylic acid (CH-HCA), 1,3,5-cyclohexanetricarboxylic acid (CH-TCA), 1,2,3,4-cyclopentanetetracarboxylic acid (CP-TCA), and 1,2,3,4-tetrahydrofurantetracarboxylic acid (THF-TCA) in combination with sodium hypophosphite (SHP) as catalyst. The amount of PCA that reacted with the cellulosic material was determined by means of isocratic HPLC (Aminex HPX-87-H). The results clearly indicate that the cyclic PCA are less effective in respect of durable press performance. CH-TCA does not react with the cellulosic material thus confirming the assumption that the crosslinking reaction between PCA and the cellulose proceeds via a five-membered cyclic anhydride.