Capillary electrophoresis separation of vinpocetine and related compounds: prediction of electrophoretic mobilities in partly aqueous media

Offord's equation, a relationship between electrophoretic mobility and charge, size and shape of peptides, has been extended to quantitate the electrophoretic mobility of vinca alkaloids. Partly aqueous protonation constants and the derived theoretical mobilities have been proven to be able to predict experimental electrophoretic mobilities. In practice, seven vincamine derivatives of very low water-solubility were separated by capillary electrophoresis. Buffer total concentration, apparent pH and methanol content, the three most important parameters of the running buffer, were used in triangular resolution mapping to characterize separation. Even though electrophoresis is well known to slow down in partly aqueous media, under our optimized circumstances a baseline separation was achieved within 8 min in each case.     

The impact of time on the heat resistance of self-compacting high-performance concrete incorporated with recycled martials

The influence of time on the mechanical behavior of concrete after exposure to elevated temperatures has been studied. Twenty-one self-compacting high-performance concrete mixtures with different incorporation amounts of coarse recycled concrete aggregate (RCA) and three unprocessed waste powder materials have been tested at age of 270 days for residual compressive and flexural strength after exposure to fire. The results have been compared to the results for the same concrete, which have been studied at age of 90 days. A new parameter has been introduced for comparing the responses of concrete to elevated temperatures at different ages; this parameter was the “heat resistance” which expresses the total area under the curve of the relative residual strength (compressive or flexural) after exposing to six temperature degrees (20, 150, 300, 500, 600, and 800 °C). The results showed that the age of concrete has an influence on the response of concrete to elevated temperatures. The heat resistance of compressive strength enhanced with age but the concrete behaved with a tendency different to that at the age of 90 days. The heat resistance of flexural strength has not been affected or slightly decreased but not with more than 10% to that at the age of 90 days. The used waste powder materials were unprocessed waste fly ash, waste cellular concrete powder and waste perlite powder; they proved that using any of them up to 15% as a replacement for cement with 0% or 25% of RCA enhanced the concrete resistance for the fire with time. The main two reasons for changing of residual strength with the time were the changing of water content and the proceeding of hydration of the binder. In general, long ages testing properties of concrete simulate the real behavior of concrete structures accurately.

     

Biomolecular Imaging with a C60-SIMS/MALDI Dual Ion Source Hybrid Mass Spectrometer: Instrumentation,Matrix Enhancement,and Single Cell Analysis

We describe a hybrid MALDI/C₆₀-SIMS Q-TOF mass spectrometer and corresponding sample preparation protocols to image intact biomolecules and their fragments in mammalian spinal cord, individual invertebrate neurons, and cultured neuronal networks. A lateral spatial resolution of 10 μm was demonstrated, with further improvement feasible to 1 μm, sufficient to resolve cell outgrowth and interconnections in neuronal networks. The high mass resolution (>13,000 FWHM) and tandem mass spectrometry capability of this hybrid instrument enabled the confident identification of cellular metabolites. Sublimation of a suitable matrix, 2,5-dihydroxybenzoic acid, significantly enhanced the ion signal intensity for intact glycerophospholipid ions from mammalian nervous tissue, facilitating the acquisition of high-quality ion images for low-abundance biomolecules. These results illustrate that the combination of C₆₀-SIMS and MALDI mass spectrometry offers particular benefits for studies that require the imaging of intact biomolecules with high spatial and mass resolution, such as investigations of single cells, subcellular organelles, and communities of cells. Graphical Abstract

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Environment induced quantum Zeno effect in coupled microwave cavities

We model a feasible experiment involving two interacting microwave cavities with very different quality factors. An excitation is initially present in the high Q cavity. Modeling the environment as linearly coupled oscillators, we find a Zeno-like behavior which should occur when the dissipation constant is large enough as compared to the unitary coupling.     

Synthesis and cyclizations of 1-azapolyene derivatives

Imminium salts of enaminonitriles with polyenals gave stable 1-azapolyenes, which could be readily transformed to benzo- and indoloquinolizines in 1,6-electrocyclizations. Azatrienes and azatetraenes with formaldehyde and primary amines afforded pyrimido[6,1-a]isoquinolines.     

Bricks and mortar of the epidermal barrier

A specialized tissue type, the keratinizing epithelium, protects terrestrial mammals from water loss and noxious physical, chemical and mechanical insults. This barrier between the body and the environment is constantly maintained by reproduction of inner living epidermal keratinocytes which undergo a process of terminal differentiation and then migrate to the surface as interlocking layers of dead stratum corneum cells. These cells provide the bulwark of mechanical and chemical protection, and together with their intercellular lipid surroundings, confer water-impermeability. Much of this barrier function is provided by the cornified cell envelope (CE), an extremely tough protein/lipid polymer structure formed just below the cytoplasmic membrane and subsequently resides on the exterior of the dead cornified cells. It consists of two parts: a protein envelope and a lipid envelope. The protein envelope is thought to contribute to the biomechanical properties of the CE as a result of cross-linking of specialized CE structural proteins by both disulfide bonds and N(epsilon)-(gamma-glutamyl)lysine isopeptide bonds formed by transglutaminases. Some of the structural proteins involved include involucrin, loricrin, small proline rich proteins, keratin intermediate filaments, elafin, cystatin A, and desmosomal proteins. The lipid envelope is located on the exterior of and covalently attached by ester bonds to the protein envelope and consists of a monomolecular layer of omega-hydroxyceramides. These not only serve of provide a Teflon-like coating to the cell, but also interdigitate with the intercellular lipid lamellae perhaps in a Velcro-like fashion. In fact the CE is a common feature of all stratified squamous epithelia, although its precise composition, structure and barrier function requirements vary widely between epithelia. Recent work has shown that a number of diseases which display defective epidermal barrier function, generically known as ichthyoses, are the result of genetic defects of the synthesis of either CE proteins, the transglutaminase 1 cross-linking enzyme, or defective metabolism of skin lipids.     

Effect of intrinsic degrees of freedom on the quantum tunneling of a collective variable

The effect of intrinsic degrees of freedom on tunneling through a potential barrier is discussed using a BKW-like approximation. In the present work intrinsic degrees of freedom are represented by a single harmonic oscillator. The theory leads to a formula for the effect of the coupling on the decay width Γ of a metastable state. When the frequency ω of the intrinsic degree of freedom is large, then Γ → Γ_ad where Γ_ad is the decay width calculated with the adiabatic barrier. An inequality Γ ≤ Γ_ad is proved for any form of the coupling hamitonian. Corrections are discussed and are shown to be of order $\text{1}\text{M}$ where M is the mass of the tunneling coordinate. An application to fission is considered. The generalization of our formula for Γ to the case of many intrinsic degrees of freedom is given explicitly.     

The force field and rz structure of Ketene

Recently determined Coriolis coupling constants for H₂ and D₂ Ketene, centrifugal distortion constants for H₂, HD, and D₂ Ketene have enabled 16 of the 19 parameters in the general force field of Ketene to be determined with significance, the ambiguity between the choice of two sets of A₁ and B₁ species force constants being removed. The r₀ structure has been redetermined using the latest values of the rotational constants of H₂, HD, and D₂ Ketene and an r_z structure has been determined for the first time.     

The use of a germene for the synthesis of esters of alpha-germyl-substituted alpha-amino acid and alpha-aminophosphonic acid

The first alpha-germyl-substituted alpha-amino ester and alpha-germyl-substituted alpha-aminophosphonic ester have been synthesized by a one-pot reaction between the germene Mes2Ge=CR2 (CR2 = fluorenylidene) and the iminoester or iminophosphonate Ph(H)C=NCH2-Y (Y = COOMe, P(O)(OEt)2).