Interferences in clinical capillary zone electrophoresis of serum proteins

Capillary zone electrophoresis (CZE) of serum proteins has become a well-accepted method for the separation of serum proteins and for the detection of monoclonal proteins in clinical laboratories. As CZE uses ultraviolet detection for direct protein quantification, exogenous ultraviolet-absorbing substances are a novel challenge, not present in conventional gel-based methods in which protein is quantified by dye binding. This minireview gives a survey of interfering substances, including iodinated contrast agents and antibiotics.     

Synthesis, characterization, and coupling reactions of six-membered cyclic P-chiral ammonium phosphonite-boranes; reactive H-phosphinate equivalents for the stereoselective synthesis of glycomimetics

Stereoselective syntheses of P-chiral ammonium phosphonite-borane complexes in the gluco- and manno-like series have been developed from P(V) phostone derivatives. The coupling reactions of these phostone donors with alcohols have been investigated with particular emphasis on the influence of protecting groups and conditions on stereoselectivity. The phosphonite-borane complexes may be applied directly in the coupling reactions and the products oxidized in situ to give phostone-mimetics of disaccharides. On the basis of these studies, successful protocols were established for the synthesis of β-gluco and α- and β-manno-configured phostones of primary alcohols. Deprotection of the dimeric compounds leads to novel families of α- or β-(1→6)-linked glycomimetics.     

Enthalpic determinations of aliphatic ester-solvent systems with correlations

Calorimetric measurements were carried out on ester-solvent systems where the esters were H(CH₂)_xCOO(CH₂)_yH, with x and y varying from 1 to 5, and the solvents were n-hexane and 1,2-dichloroethane. Calculation of the enthalpies of cavity formation enabled the enthalpies of interaction to be determined. Both enthalpies correlated with number of carbon atoms N, equal to x+y in the esters, giving for 1,2-dichloroethane

“In situ” extraction of essential oils by use of Dean–Stark glassware and a Vigreux column inside a microwave oven: a procedure for teaching green analytical chemistry

One of the principal objectives of sustainable and green processing development remains the dissemination and teaching of green chemistry in colleges, high schools, and academic laboratories. This paper describes simple glassware that illustrates the phenomenon of extraction in a conventional microwave oven as energy source and a process for green analytical chemistry. Simple glassware comprising a Dean-Stark apparatus (for extraction of aromatic plant material and recovery of essential oils and distilled water) and a Vigreux column (as an air-cooled condenser inside the microwave oven) was designed as an in-situ extraction vessel inside a microwave oven. The efficiency of this experiment was validated for extraction of essential oils from 30 g fresh orange peel, a by-product in the production of orange juice. Every laboratory throughout the world can use this equipment. The microwave power is 100 W and the irradiation time 15 min. The method is performed at atmospheric pressure without added solvent or water and furnishes essential oils similar to those obtained by conventional hydro or steam distillation. By use of GC-MS, 22 compounds in orange peel were separated and identified; the main compounds were limonene (72.1%), β-pinene (8.4%), and γ-terpinene (6.9%). This procedure is appropriate for the teaching laboratory, does not require any special microwave equipment, and enables the students to learn the skills of extraction, and chromatographic and spectroscopic analysis. They are also exposed to a dramatic visual example of rapid, sustainable, and green extraction of an essential oil, and are introduced to successful sustainable and green analytical chemistry.     

Characterization of rhinovirus subviral A particles via capillary electrophoresis, electron microscopy and gas-phase electrophoretic mobility molecular analysis: Part I

During infection, enteroviruses, such as human rhinoviruses (HRVs), convert from the native, infective form with a sedimentation coefficient of 150S to empty subviral particles sedimenting at 80S (B particles). B particles lack viral capsid protein 4 (VP4) and the single-stranded RNA genome. On the way to this end stage, a metastable intermediate particle is observed in the cell early after infection. This subviral A particle still contains the RNA but lacks VP4 and sediments at 135S. Native (150S) HRV serotype 2 (HRV2) as well as its empty (80S) capsid have been well characterized by capillary electrophoresis. In the present paper, we demonstrate separation of at least two forms of subviral A particles on the midway between native virions and empty 80S capsids by CE. For one of these intermediates, we established a reproducible way for its preparation and characterized this particle in terms of its electrophoretic mobility and its appearance in transmission electron microscopy (TEM). Furthermore, the conversion of this intermediate to 80S particles was investigated. Gas-phase electrophoretic mobility molecular analysis (GEMMA) yielded additional insights into sample composition. More data on particle characterization including its protein composition and RNA content (for unambiguous identification of the detected intermediate as subviral A particle) will be presented in the second part of the publication.     

Spatial control of p-n junction in an organic light-emitting electrochemical transistor

Low-voltage-operating organic electrochemical light-emitting cells (LECs) and transistors (OECTs) can be realized in robust device architectures, thus enabling easy manufacturing of light sources using printing tools. In an LEC, the p-n junction, located within the organic semiconductor channel, constitutes the active light-emitting element. It is established and fixated through electrochemical p- and n-doping, which are governed by charge injection from the anode and cathode, respectively. In an OECT, the electrochemical doping level along the organic semiconducting channel is controlled via the gate electrode. Here we report the merger of these two devices: the light-emitting electrochemical transistor, in which the location of the emitting p-n junction and the current level between the anode and cathode are modulated via a gate electrode. Light emission occurs at 4 V, and the emission zone can be repeatedly moved back and forth within an interelectrode gap of 500 μm by application of a 4 V gate bias. In transistor operation, the estimated on/off ratio ranges from 10 to 100 with a gate threshold voltage of -2.3 V and transconductance value between 1.4 and 3 μS. This device structure opens for new experiments tunable light sources and LECs with added electronic functionality.     

Nature and structure of aluminum surface sites grafted on silica from a combination of high-field aluminum-27 solid-state NMR spectroscopy and first-principles calculations

The determination of the nature and structure of surface sites after chemical modification of large surface area oxides such as silica is a key point for many applications and challenging from a spectroscopic point of view. This has been, for instance, a long-standing problem for silica reacted with alkylaluminum compounds, a system typically studied as a model for a supported methylaluminoxane and aluminum cocatalyst. While (27)Al solid-state NMR spectroscopy would be a method of choice, it has been difficult to apply this technique because of large quadrupolar broadenings. Here, from a combined use of the highest stable field NMR instruments (17.6, 20.0, and 23.5 T) and ultrafast magic angle spinning (>60 kHz), high-quality spectra were obtained, allowing isotropic chemical shifts, quadrupolar couplings, and asymmetric parameters to be extracted. Combined with first-principles calculations, these NMR signatures were then assigned to actual structures of surface aluminum sites. For silica (here SBA-15) reacted with triethylaluminum, the surface sites are in fact mainly dinuclear Al species, grafted on the silica surface via either two terminal or two bridging siloxy ligands. Tetrahedral sites, resulting from the incorporation of Al inside the silica matrix, are also seen as minor species. No evidence for putative tri-coordinated Al atoms has been found.     

The initial step of silicate versus aluminosilicate formation in zeolite synthesis: a reaction mechanism in water with a tetrapropylammonium template

The initial step for silicate and aluminosilicate condensation is studied in water in the presence of a realistic tetrapropylammonium template under basic conditions. The model corresponds to the synthesis conditions of ZSM5. The free energy profile for the dimer formation ((OH)(3)Si-O-Si-(OH)(2)O(-) or [(OH)(3)Al-O-Si-(OH)(3)](-)) is calculated with ab initio molecular dynamics and thermodynamic integration. The Si-O-Si dimer formation occurs in a two-step manner with an overall free energy barrier of 75 kJ mol(-1). The first step is associated with the Si-O bond formation and results in an intermediate with a five-coordinated Si, and the second one concerns the removal of the water molecule. The template is displaced away from the Si centres upon dimer formation, and a shell of water molecules is inserted between the silicate and the template. The main effect of the template is to slow down the backward hydrolysis reaction with respect to the condensation one. The Al-O-Si dimer formation first requires the formation of a metastable precursor state by proton transfer from Si(OH)(4) to Al(OH)(4)(-) mediated by a solvent molecule. It then proceeds through a single step with an overall barrier of 70 kJ mol(-1). The model with water molecules explicitly included is then compared to a simple calculation using an implicit continuum model for the solvent. The results underline the importance of an explicit and dynamical treatment of the water solvent, which plays a key role in assisting the reaction.