Does the chromatomembrane cell improve the quality of environmental analysis?

With the intention of combining partition chromatography and membrane techniques, we succeeded in developing the chromatomembrane cell which has proved to be reliable as an extraction and preconcentration manifold in flow injection analysis. With this technique, two immiscible phases can be induced to flow independently through a block of biporous (macro and micro) PTFE in order to promote analyte exchange. Consequently, the application of chromatomembrane cells in environmental analysis resolves all problems of sample pretreatment simply and effectively whenever a preconcentration step by gas/liquid or liquid/liquid solvent extraction is included. The link-up with analyzers (AAS, UV–Vis photometry, GC, IC, HPLC, voltammetry, ion selective electrodes, etc.) makes possible computer aided automization for environmental monitoring.     

Improvement of the stability of NiO–YSZ anode material for solid oxide fuel cell

Improvement of long-term stability of 40vol.%NiO–60vol.% yttria-stabilized zirconia (YSZ) anode material in reducing atmosphere and under exposure to thermal shock through the modification of vacancy concentration and pore shape has been investigated for a solid oxide fuel cell. We varied the amount of Y₂O₃ additives from 8 to 10 mol% in YSZ and the type of carbon pore former, from plated activated carbon to spherical carbon black, to improve the strength and the stability of porous NiO–YSZ anode materials. Modifications by varying the amount of Y₂O₃ additives and carbon pore former result in a highly stable anode, even upon exposure to a reducing atmosphere for 1,200 h. In particular, the strengths of the new anode materials are markedly improved at the same porosity level. Higher strengths do not degrade during a longtime durability test in a reducing atmosphere or upon thermal shock testing. The relatively smaller degradation of electrical conductivity of the new anode material is discussed in terms of the possibility of suppression of the disconnectivity of Ni phases during operation of a solid oxide fuel cell.     

Synthesis of an external β-turn based on the GLDV motif of cell adhesion proteins

The (3S,6S,10S)-7/5 bicyclic lactam 4, designed as an external turn constraint, was synthesised by a new stereoselective route involving Eschenmoser condensation. Calculated preferred conformations compare well with the preferred solid state conformation, obtained by X-ray crystallography. The lactam 4 was not a turn mimic in its own right but could be used as an external constraint to prepare the cyclic peptide 29 containing the integrin recognition motif GLDV. High-resolution NMR measurements were consistent with this compound having a single backbone conformation.     

Tetrameric RGD induces clustering of integrin αvβ3 on the melanoma cell surface and decreases cell viability

The recombinant hybrid protein SR15 composed of streptavidin fused with RGD peptide is obtained. The ability of this protein to recognize human melanoma cells (MeWo line) is demonstrated. Types of expressed RGD-binding integrins in the cells of this line are identified. It is found that the recombinant hybrid protein SR15 binds to integrin αvβ3 on the surface of human melanoma cells. The binding to the protein SR15 results in clustering of αvβ3 receptors on the surface of MeWo cells, internalization of the recombinant protein, and an almost twofold decrease in cell viability.     

Synthesis of Nafion~-stabilized Pt nanoparticles to improve the durability of proton exchange membrane fuel cell

Nafion-stabilized Pt nanoparticle colloidal solution is synthesized through ethylene glycol reduction.Pt/Nafion added with carbon black as electric conduction material(labeled Pt/Nafion-XC72) shows excellent electrochemical property compared with Pt/C.After a 300-cycle discharging durability test,the cell performance of membrane electrode assembly(MEA) with the Pt/Nafion-XC72 and Pt/C catalysts indicates a 29.9% and 92.2% decrease,respectively.The charge transfer resistances of Pt/Nafion-XC72 and Pt/C increase by 27.2% and 101.9%,respectively.The remaining electrochemically active surface area of Pt is about 61.7% in Pt/Nafion-XC72 and about 38.1% in Pt/C after the durability test.The particle size of Pt/C increases from about 5.1 nm to about 10.8 nm but only from 3.6 nm to 5.8 nm in the case of Pt/Nafion-XC72.These data suggest that Pt/Nafion-XC72 as a catalyst can enhance the durability of PEMFCs compared with Pt/C.     

Does the nanometre scale topography of titanium influence protein adsorption and cell proliferation?

To investigate the influence of titanium films with nanometre scale topography on protein adsorption and cell growth, three different model titanium films were utilized in the present study. The chemical compositions, surface topographies and wettability were investigated by using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and water contact angle measurement, respectively. The films share the same surface chemistry but exhibit different topographies on a nanometre scale. Thus, they act as model systems for biological studies regarding surface topography effects. The films were obtained by varying the deposition rate and the film thickness, respectively. These films displayed nanometre scale surface roughness (root mean square roughness, R_rms) from 2 to 21 nm over areas of 50 μm × 50 μm, with different grain sizes at their surfaces. Albumin and fibrinogen adsorption on these model titanium films were performed in this study. Bicinchoninic acid assay was employed to determine the amount of adsorbed protein on titanium film surfaces. No statistically significant differences, however, were observed for either albumin or fibrinogen adsorption between the different groups of titanium films. No statistically significant influence of surface roughness on osteoblast proliferation and cell viability was detected in the present study.     

A multivariate insight into the in vitro antitumour screen database of the National Cancer Institute: classification of compounds, similarities among cell lines and the influence of molecular targets

A multivariate insight into the in vitro antitumour screen database of the NCI by means of the SIMCA package allows to propose hypotheses on the mechanism of action of novel anticancer compounds. As an example, the application of multivariate analysis to the NCI standard database provided clues to the classification of drugs whose mechanism is either unknown or controversial. Moreover, the influence of intrinsic biochemical cell line properties (molecular targets) on the sensitivity to drug treatment could be evaluated simultaneously for classes of compounds which act by the same mechanism. Interestingly, the present approach can also provide a correlation between the molecular targets and the therapeutical fingerprint of novel active compounds thus suggesting specific biochemical studies for the investigation of new mechanisms of drug action and resistance. The statistical approach reported here represents a valuable tool for handling theenormous data sets deriving from recent genome-wide investigations of gene expression in the NCI cell lines.     

Synthesis of the fragment GlcNAc-α(1→p→6)-GlcNAc of the cell wall polymer of staphylococcus lactis having repeating N-acetyl-D-glucosamine phosphate units

The monofunctional phosphitylating reagents chloro-β-cyanoethyl-N,N-diisopropylamino-phosphoramidite ($\text{3}$) and salicylchlorophosphite ($\text{4}$) have been applied towards the introduction of an α(1→6) interglycosidic phosphodiester bond between two properly-protected N-acetyl-D-glucosamine units. Evidence will be presented to show that $\text{4}$ gives a higher yield of the required dimer than $\text{3}$.     

Synthesis of a flavonoid fluorescent probe for the detection of sulfur dioxide derivatives and cell imagingEI北大核心CSCD

A novel fluorescent probe HMQC was synthesized for HSOf detection by coupling flavonoid derivatives with 3-quinoline salt. In PBS buffer solution, the probe showed high selectivity, good sensitivity (58 nmol/L) and rapid response (150 s) for the detection of HSO3−. The possible sensing mechanism of the probe was discussed by nuclear magnetic hydrogen spectroscopy, mass spectrometry and theoretical calculation, indicating that the addition reaction between HSO3− and the C=C bond of the probe led to the fluorescence enhancement. The probe HMQC could be used for the detection of HSO3− in living cells, making it to be a promising tool for delecting HSO3−. © 2023, Youke Publishing Co.,Ltd. All rights reserved.     

Computer aided simulation of hydrogen–oxygen (air) fuel cell with regard to the degradation mechanism of platinum catalyst on the cathode

A mathematical model of a hydrogen–oxygen (air) fuel cell that takes into account the phenomena of degradation of the cathodic platinum catalyst is presented. For potential cycling from 0.6 to 1.1 V with a scan rate of 0.1 V/s, depending on the platinum loadings, the following factors are found to prevail in the mechanism of electroactive surface degradation: the coalescence of platinum nanoparticles at large loadings and the platinum dissolution/redeposition and diffusion to the membrane at medium and low loadings. Based on mathematical simulation, the data on the discharge curves are calculated. The observed decrease in the discharge characteristics is attributed to the degradation of the catalyst active surface and the increased transport losses during accelerated stress testing.     

Evaluating membrane cell e.m.f.ś from different schems of integration of the relevant nernstian equations

Computing the e.m.f. E (and the related membrane potential E_M) of the general concentration cell: electrode J ¦ IJ (m₁) in S ¦ membrane I ¦ IJ (m₂) in S ¦ electrode J (where the membrane perm-selective to counterion I separates two solutions of molalities m₁ and m₂ of the same electrolyte IJ, one mole of which forms n_I moles of I of valency z_I and n_J moles of coion J of valency z_J, with n=n_I+n_J) requires integration between limits m₁ and m₂ of the differential equation: dE=[nRT/Fn_J|z_J|] [τ_Iz_I, - mτ_sM_s]dln(mγ)_IJ, where the transference numbers τ_I of I and τ_s of the solvent S through the membrane are customarily taken as constant. The key point is the integration of the term mdln(mγ), which in the current practice is oversimplified to give [(m₁ + m₂)/2] in (m₂γ₂/m₁γ₁), and may cause large overestimation of the solvent-transfer contribution, with unreliable results for E and E_M. The procedure recommended here is instead that of splitting

mdln(mγ) into the “ideal part”

mdlnm=m₂-m₁ and the “non-ideal part”

mdlnγ, the latter being safely integrable putting lnγ as an explicit function of m in terms of the extended Debye-Hückel equation. Alternative and equally reliable procedures are described.     

Carbothermal reduction of the YSZ–NiO solid oxide fuel cell anode precursor by carbon-based materials

The thermal behavior of the yttria-stabilized zirconia (YSZ) and nickel oxide (YSZ–NiO) composite mixtures with the addition of graphite, multiwall carbon nanotubes and functionalized multiwall carbon nanotubes was studied. The YSZ–NiO composite is the precursor of the YSZ–Ni anode of solid oxide fuel cells. The anode exhibits a porous structure, which is usually obtained by the addition of carbon containing pore formers. Thermal analysis and X-ray diffraction evidenced that the properties of carbonaceous materials (C) and atmosphere have a strong influence on the thermal evolution of the reactions taking place upon heating the anode precursor. The dependence of both the carbon content and the chemical nature of the ceramic matrix on the thermal behavior of the composite were investigated. The discussed results evidenced important features for optimized processing of the anode.     

Synthesis of 4-hetero-16α,17α-cyclohexanopregnanes and evaluation of their cytotoxicity against the HeLa cell line

Russian Chemical Bulletin - The oxidation of the ring A of 16α,17α-cyclohexanoprogesterone gave 5-oxo-A-nor-3,5-secopregnan-3-oic acid. The subsequent ring A closure in the latter...     

Aluminum enhances the toxic effects of amyloid β-peptide on cell membranes and a molecular model

Abstract  

The amyloid β-peptide (Aβ) and aluminum are found, among other components, in the senile plaques of patients with Alzheimer’s disease. Aggregated Aβ and aluminum are toxic to neurons but the mechanism of accumulation and toxicity remains poorly understood. It has been proposed that Aβ and aluminum toxicity results from Aβ– and aluminum–membrane interactions. It was therefore of interest to study the effect that Aβ and aluminum could have on cell membranes. Thus, the interactions of Aβ(1-40), Aβ(1-42), and Al(III) with the human erythrocyte membrane and a molecular model of the erythrocyte membrane were examined by electron microscopy and X-ray diffraction, respectively. The molecular model consisted of bilayers built up of dimyristoylphosphatidylcholine and dimyristoylphosphatidylethanolamine, phospholipid classes located in the outer and inner monolayers of most cell membranes, respectively. Aβ(1-40) and Aβ(1-42) in the presence of Al(III) altered the erythrocyte membrane morphology and the structure of dimyristoylphosphatidylcholine bilayers, effects that were different and stronger than those induced by Aβ and Al(III) separately.     

Anionic polymerization of ϵ-caprolactam-lix effect of the ratio of reacting components,of the medium and of the ring size on the initial stage of the anionic polymerization of lactams

Effects of the concentrations and ratio of reacting components and of temperature on the kinetics of reaction of N-propionyllactam (I) with potassium salt of lactam (KL) were studied for derivatives of ϵ-caprolactam, 8-octanelactam and 12-dodecanelactam. For ϵ-caprolactam, the initial rates of propagation, acylation of open-chain amide groups and condensation of growth centres were estimated. At the ratio of the starting components [I]₀/[KL]₀ = 0.5-3, the participation of the polymerization reaction is constant, amounting to ca 45% of the overall consumption of 1. The condensation reaction is 14–36% of the total consumption of I; its initial rate passes through a maximum at [I]₀/[KL]₀ = 2. With increasing permittivity of the medium, the total rate of consumption of I increases; in two media with the same bulk permittivity, however, the rates may differ by as much as one order of magnitude.     

Construction of the Skeleton of Phthalascidin, Mechanism of the Formation of the Key Tricyclic Lactam Intermediate

Phthalascidin is a structurally simplified version of Et-743, which is a potent anti-tumor marine natural product isolated from Ecteinascidia turbinata. Its antiproliferative activity is greater than that of the agents taxol, camptothecin, adriamycin, mitomycin C, cisplatin, bleomycin, and etoposide by 1-3 orders of magnitude. An elegant synthesis of Et-743 and phthalascidin has been reported by E. J. Corey and co-workers1,2. As part of our continuing program, we have also engaged in dev…     

Synthesis of two peptides of α-bungarotoxin and the participation of the amino acid residue Trp-28 of the neurotoxin in the antigenicity of the molecule

Using the method of solid-phase peptide synthesis, two peptides have been synthesized, one of which corresponds to the central ring structure of -bungarotoxin (-BTX), while the second has in position 28 a Gly residue in place of the Trp in the first peptide, and their interrelationship with antitoxin antibodies has been investigated. It has been shown that the amino acid residue Trp-28 of -BTX, which is the contact residue in binding with the acetylcholine receptor, also participates directly in binding with the active centers of antibodies to -BTX.Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 628–631, July–August, 1997.     

Studies of the dissociation and the protonation of TB-chlorosulphophenol

The dissociation constant of each step for TB-chlorosulphophenol has been determined by potentiometric method, and the thermodynamic constants, △G°, △H° and △S°, of the dissociation process have been calculated. The protonation constants were measured by the spectrophotometric method. The pH values of various forms of anions of the chromogenic reagent at their concentrations were also calculated.     

Biosynthesis of β-sitosterol and stigmasterol proceeds exclusively via the mevalonate pathway in cell suspension cultures of Croton stellatopilosus

Cell suspension cultures of Croton stellatopilosus were fed with [1-¹³C]glucose and [2-¹³C]sodium acetate and cultured under control conditions. β-Sitosterol and stigmasterol were isolated and their ¹³C-labeling patterns examined using quantitative NMR spectroscopy. Analysis of the patterns of ¹³C-enrichment revealed that all the isoprene units in the molecules of both phytosterols originated exclusively from the mevalonate pathway. These results were in contrast with our previous study using callus cultures of C. stellatopilosus, which showed that the isoprene units of β-sitosterol and stigmasterol were supplied equally from both the deoxyxylulose phosphate (DXP) pathway and the mevalonate pathway. Observation by transmission electron microscopy of sub-cellular structures of both cell types revealed that the callus cells contained partially differentiated chloroplasts, whereas the suspension cultured cells did not. Since the DXP pathway is known to be located in the chloroplasts, it was suggested that the presence of chloroplasts is essential for expression of the DXP pathway. Therefore, the sole operation of the phytosterol biosynthesis by the mevalonate pathway observed in this study was likely to be the result of non-expression of the DXP pathway in the chloroplast-free cell suspension cultures of C. stellatopilosus.