Sequential fractionation procedure for the identification of potentially cytochrome P4501A-inducing compounds

A multistep fractionation procedure for the separation of nonpolar aromatic compounds with respect to cytochrome P4501A induction is presented. Normal-phase HPLC on nitrophenylpropyl silica and cyanopropyl silica was tested for group-specific separation as a first fractionation step. Subsequent individual compound-specific PAH fractionation was done by means of reversed-phase HPLC. Electron-donor-acceptor HPLC and size-exclusion chromatography were applied to separate PAHs, PCBs, PCNs and PCDD/Fs according to their number of aromatic carbon atoms, their hydrophobicity, their degree of chlorination, their planarity and their molecular size. The method was validated for complex environmental mixtures on the basis of two sediment extracts.     

Protein-cation interactions: structural and thermodynamic aspects

Cations are specifically recognized by numerous proteins. Cations may play a structural role, as cofactors stabilizing their binding partners, or a functional role, as cofactors activating their binding partners or being themselves involved in enzymatic reactions. Despite their small size, their charge density and their specific interaction with highly charged residues allow them to induce significant conformational changes on their binding proteins. The protein conformational change induced by cation binding may be as large as to account for the complete folding of a protein (as evidenced in Hepatitis C NS3 protease, or human rhinovirus 2A protease), and they may also trigger oligomerization (as in calcium-binding protein 1). Especially intriguing is the ability of cation-binding proteins of discriminating between very similar cations. In particular, calcium and magnesium are recognized by proteins with markedly different binding affinities and cause significantly different conformational changes and stabilization effects in the binding proteins (as in the fifth ligand binding repeat of the LDL receptor binding domain, calcium-binding protein 1, or parvalbumin). This article summarizes recent findings on the structural and energetic impact of cation binding to different proteins. A general framework can be envisaged in which cations can be considered as a special type of allosteric effectors able to modulate the functional properties of proteins, in particular the ability to interact with biological targets, by altering their conformational equilibrium.     

卟啉及其光电化学研究进展

卟啉及金属卟啉在自然界中广泛存在,其光学、电化学等特性可通过分子结构中多个反应位点进行调控. 随着全球能源环境问题日益凸显,卟啉在太阳能电池、光催化制氢领域的研究成为热点. 本文简介了作者课题组近年来通过国内外合作开展的D-π-A结构卟啉分子结构改性及其对光电化学性质和器件光伏特性影响的进展,并对未来卟啉光电化学研究的发展进行了简要的探讨.     

Column purification and HPLC determination of teicoplanin and A40926

Summary A simple HPLC method for quali- and quantitative determination of teicoplanin and A40926 in fermentation broths and in biological fluids is described. The sample is purified on affinity chromatography and then analyzed on a reverse phase column using a gradient phosphate buffer-acetonitrile as mobile phase and UV detection at 254 nm. No interference from endogenous sources has been observed. The analytical method, with partial modifications, was also used to isolate on semipreparative scale the single components of these antibiotics, in order to investigate their structure and their biological activity.     

A Study On Air Pollution by Asphalt Fumes

Abstract

A TLC/HPLC procedure for the determination of polycyclic aromatic hydrocarbons (PAH), occuring in asphalt fumes (adsorbed on particular matter), is described. The method is based on extraction of asphalt fume particles, collected on glass fibre filters, using CCK₄. Following a clean up step by the aid of a TLC procedure on Al₂ O₃ thinlayer plates, using a mixture of cyclohexane/acetone/ether as the mobile phase. Under UV-light, occuring PAH are indicated as fluorescent spots. A separation of the collected PAH into individual components and their identification is performed by the aid of a HPLC procedure. Futher-more, an approach was made to verify the separated PAH by their fluorescence spectra and their mass spectra.     

Materials design for perovskite SOFC cathodes

Abstract  

This article focuses on perovskite materials for application as cathode material in solid oxide fuel cells. In order to develop new promising materials it is helpful to classify already known perovskite materials according to their properties and to identify certain tendencies. Thereby, composition-dependent structural data and materials properties are considered. Structural data under consideration are the Goldschmidt tolerance factor, which describes the stability of perovskites with respect to other structures, and the critical radius and lattice free volume, which are used as geometrical measures of ionic conductivity. These calculations are based on the ionic radii of the constituent ions and their applicability is discussed. A potential map of perovskites as a tool to classify simple ABO₃ perovskite materials according to their electrical conduction behavior is critically reviewed as a structured approach to the search for new cathode materials based on more complex perovskites with A and/or B-site substitutions. This article also covers the approaches used to influence electronic and the ionic conductivity. The advantage of mixed ionic electronic conductors in terms of the oxygen exchange reaction is addressed and their important properties, namely the oxygen-exchange coefficient and the oxygen diffusion coefficient, and their effect on the oxygen reduction reaction are presented.     

Immobilizing sulfotransferase 1A1 on magnetic microparticles and their evaluation using capillary electrophoresis

Sulfotransferases are categorized as phase II metabolic enzymes. Human sulfotransferase 1A1 (SULT1A1) is involved in the sulfonation of xenobiotics with aid from the cofactor 3'‐phosphoadenosine‐5'‐phosphosulfate that acts as a sulfonate donor. In this study, we have attempted to immobilize SULT1A1 on magnetic microparticles (MMs). Different functionalized MMs were used to immobilize SULT1A1 and their enzyme activity was compared to the control (enzyme in solution). Paracetamol was used as model substrate. Separation of paracetamol and paracetamol sulfate by CE‐UV was optimized and validated. MMs with epoxy based immobilization of SULT1A1 showed better enzyme activity. Hence, they were tested for repeated usage to allow their implementation for the development of a CE immobilized micro enzyme reactor.     

Recent studies on small molecular and polymeric hole-transporting materials for high-performance perovskite solar cells

A decade of significant research has led to the emergence of photovoltaic solar cells based on perovskites that have achieved an exceptionally high-power conversion efficiency of 26.08%. A key breakthrough in perovskite solar cells (PSCs) occurred when solid hole-transporting materials (HTMs) replaced liquid electrolytes in dye-sensitized solar cells (DSSCs), because HTMs play a crucial role in improving photovoltaic performance as well as cell stability. This review is mainly focused on the HTMs that are responsible for hole transport and extraction in PSCs, which is one of the crucial components for efficient devices. Here, we have reviewed small molecular as well as polymeric HTMs that have been reported in the last two years and discussed their performance based on the analysis of their molecular architectures. Finally, we include a perspective on the molecular engineering of new functional HTMs for highly efficient stable PSCs.     

Acid–Base‐Responsive Intense Charge‐Transfer Emission in Donor–Acceptor‐Conjugated Fluorophores

Herein we report on the synthesis and acid‐responsive emission properties of donor–acceptor (D–A) molecules that contain a thienothiophene unit. 2‐Arylthieno[3,2‐b]thiophenes were conjugated with an N‐methylbenzimidazole unit to form acid‐responsive D–A‐type fluorophores. The D–A‐conjugated fluorophores showed intense intramolecular charge‐transfer (ICT) emission in response to acid. The effect of the substitution on their photophysical properties as well as their solvent‐dependence indicated non‐twisting ICT emission in protonated D–A molecules. The quinoidal character of 2‐arylthienothiophene as a donor part is discussed, as it is assumed that it contributes to suppression of the molecular twisting in the excited state, therefore decreasing the nonradiative rate constant, thereby resulting in the intense ICT emission. Acid–base‐sensitive triple‐color emission was also achieved by the introduction of a base‐responsive phenol group in the donor part.     

Mass spectrometric study of six cyclic esters

A series of cyclic esters, which are optically active as a consequence of their helical structures, were synthesized to investigate the relationships between their structures and their optical activities. This paper reports the electron impact fragmentation mechanisms of these six cyclic esters. Accurate mass measurements and mass analyzed ion kinetic energy spectrometry confirmed fragmentation patterns. The stability of the fragment ions has a great influence on the fragmentation pathways, but no correlation with the optical activity was found.     

Anti-inflammatory and analgesic activity of Alkanna bracteosa and Alkanna tricophila

Alkanna bracteosa and Alkanna tricophila, Boraginaceae, have been reported to be useful for their anti-inflammatory and wound-healing effects in traditional medicine. Methanol extracts of A. bracteosa and A. tricophila were evaluated for their potential analgesic and anti-inflammatory properties. Alkanna bracteosa was observed to produce a maximum of 42% reduction of hind paw licking in acute as well as 68% alleviation in inflammatory phase of formalin test in mice and about 30% declination of carrageenan-induced rats paw swelling at doses 100-400?mg?kg?1 in comparison to negative control; on the other hand, A. tricophila required at least 200?mg?kg?1 to exhibit a significant reduction in paw licking or oedemas at the early phase of formalin test and the late phase of carrageenan test, respectively. Our results suggest that the extracts may be of use for their analgesic and anti-inflammatory effects.     

Differential diffusion effects on buoyancy-driven instabilities of acid-base fronts: the case of a color indicator

Buoyancy-driven hydrodynamic instabilities of acid-base fronts are studied both experimentally and theoretically in the case where an aqueous solution of a strong acid is put above a denser aqueous solution of a color indicator in the gravity field. The neutralization reaction between the acid and the color indicator as well as their differential diffusion modifies the initially stable density profile in the system and can trigger convective motions both above and below the initial contact line. The type of patterns observed as well as their wavelength and the speed of the reaction front are shown to depend on the value of the initial concentrations of the acid and of the color indicator and on their ratio. A reaction-diffusion model based on charge balances and ion pair mobility explains how the instability scenarios change when the concentration of the reactants are varied.     

Cell aggregation by scaffolded receptor clusters

The aggregation of cells by lectins or antibodies is important for biotechnological and therapeutic applications. One strategy to augment the avidity and aggregating properties of these mediators is to maximize the number of their ligand binding sites. The valency of lectins and antibodies, however, is limited by their quaternary structures. To overcome this limitation, we explored the use of polymers generated by ring-opening metathesis polymerization (ROMP) as scaffolds to noncovalently assemble multiple copies of a lectin, the tetravalent protein concanavalin A (Con A). We demonstrate that complexes between Con A and multivalent scaffolds aggregate cells of a T cell leukemia line (Jurkat) more effectively than Con A alone. We anticipate that synthetic scaffolds will offer a new means of facilitating processes that rely on cell aggregation, such as pathogen clearance and immune recognition.     

Phaeophytin analogues from Ligularia knorringiana

A new phaeophytin, ligulariaphytin A, together with five known phaeophytins, were isolated from the aerial parts of Ligularia knorringiana. The structure of ligulariaphytin A was elucidated as 131-hydroxy-131,132-peroxyphaeophorbide A ethyl ester, and the five known compounds were identified as 132-hydroxyphaeophorbide A ethyl ester, 173-ethoxyphaeophorbide A, phaeophytin B, phaeophytin A, and phaeophorbide B ethyl ester, respectively, based on spectroscopic analysis and by comparison of their spectral data with those reported previously in the literature. All compounds were evaluated for their in vitro cytotoxic activities against cultured Hela cell, and were found to show only very weak cytotoxicity.     

Amino sulfonic acids,peptidosulfonamides and other related compounds

A review with 636 references. The literature on saturated amino sulfonic acids with primary/secondary amino group and their derivatives from XIX century to 2016 is surveyed, focusing mainly on results published in the last two decades. Synthesis of saturated amino sulfonic acids and their derivatives, their occurrence among natural products, as well as their use for design of peptidomimetics, conjugates with various molecules of practical significance, applications as building blocks for drug discovery and for other reasons are discussed.     

Synthetic study on the relationship between structure and sweet taste properties of steviol glycosides

The structure activity relationship between the C??-C?? methylene double bond on the aglycone of steviol glycosides and the corresponding impact on their sweet taste has been reported here for the first time. It has been observed that converting stevioside and rebaudioside A to their corresponding ketones by switching the doubly bonded methylene on C-17 for a ketone group actually removes the sweet taste properties of these molecules completely. Regenerating the original molecules tends to restore the sweet taste of both the steviol glycosides. Thus this C??-C?? methylene double bond in rebaudioside A and stevioside can be regarded as a pharmacophore essential for the sweetness property of these molecules.     

Comparison of thermodynamic and rheological properties of binary polymer mixtures

The dependence of viscosity on concentration for a series of binary mixtures of polymers differing in their chemical nature and for mixtures of polymer homologues was compared with the peculiarities of their phase diagrams as well as with the concentration dependence of their thermodynamic interaction parameters. A definite correlation was found between the composition dependence of the viscosity and the thermodynamic state of the system in the melt at a given temperature. The universal character of this correlation was shown both for the mixtures of various polymers and for those of the polymer homologues.     

Biomimetic Synthesis of Complex Flavonoids Isolated from Daemonorops “Dragon's Blood”

The dragonbloodins are a pair of complex flavonoid trimers that have been isolated from the palm tree Daemonorops draco, one of the sources of the ancient resin known as “dragon's blood”. We present a short synthesis that clarifies their relative configurations and sheds light on their origin in Nature. This synthesis features biomimetic cascade reactions that involve both ionic and radical intermediates. The biogenetic relationships between dracorhodin, the dracoflavans C, and the dragonbloodins A1 and A2 are discussed.     

Insulated π-conjugated metallopolymers

Recently, there has been a progressive development of insulated π-conjugated metallopolymers with accumulated features of π-conjugated bridging units, transition metal complexes, and encapsulating moieties, as higher-order functionalized materials. A number of insulated conjugated metallopolymers have been successfully synthesized and their fascinating properties have been reported. In addition to the conventional features derived from π-conjugation and transition metals, their insulated structures can compensate for solubility, a disadvantage in conventional metallopolymers, and enhance their functionalities, such as sensing, luminescence, and conduction. In this review, we summarize the synthetic methodologies, structural characteristics, and functionalities of one-dimensional insulated π-conjugated metallopolymers, while focusing on the effect of transition metals and insulation on their properties.     

A Review of Silver Nanoparticles: Research Trends,Global Consumption,Synthesis, Properties,and Future Challenges

Silver nanoparticles (AgNPs) are intensively investigated for their superior physical, chemical, and biological properties. A proper knowledge of these properties is essential to maximizing the potential applications of AgNPs in several areas while minimizing their risks to humans and the environment. This paper aims to critically review AgNPs from the perspectives of research trends, global consumption, synthesis, properties, and future challenges. Generally, AgNPs can be synthesized using three methods, namely physical, chemical, and biological, and the related works as well as their numerous advantages and disadvantages are presented in this review. In addition, AgNPs can be potentially explored for various applications. Future challenges on (AgNP) synthesis, their release into the environment, and scaling up production, as presented in the review, suggest that several potential topics for future works are available to promote a safer and more efficient use of these nanoparticles. Studies on AgNPs in Malaysia have increased since the Malaysian government officially established a directorate for nanotechnology development. This calls for a proper set of policies on AgNPs starting from their production to utilization as well as their effects on various related industries and the environment.