Journal Articles on Category: Chemistry

In the title compound, [Ca(C32H24N3O2P2)2], the 1,3-bis(diphenylphosphinoylimino)isoindoline ligand adopts a tridentate coordination mode. The compound exhibits a distorted octahedral geometry. The Ca atom lies on a twofold rotation axis.

Issn:16005368

Keywords:

Volume: 64

Pages: m160-m160

This study was carried out to identify the conditions of formation of calcium sulphoaluminate (3CaO·3Al2O3·CaSO4) by the sintering of a limestone (CaCO3) and alunite [K2SO4·Al2(SO4)3·4Al(OH)3] mixture with the following reagents: K2SO4, CaCO3, Al(OH)3, CaSO4·2H2O, and SiO2. When K2SO4, CaCO3, Al(OH)3, CaSO4·2H2O were mixed in molar ratios of 1:3:6:3 and sintered at 1,200~1,300 °C, only 3CaO·3Al2O3·CaSO4 and calcium langbeinite (2CaSO4·K2SO4) were generated. With an amount of CaO that is less than the stoichiometric molar ratio, 3CaO·3Al2O3·CaSO4 was formed and anhydrite (CaSO4) did not react and remained behind. With the amount of CaSO4 that is less than the stoichiometric molar ratio, the amounts of 3CaO·3Al2O3·CaSO4 and 2CaSO4·K2SO4 decreased, and that of CaO·Al2O3 increased. In the K2SO4-CaO-Al2O3-CaSO4-SiO2 system, to stabilize the formation of 3CaO·3Al2O3·CaSO4, 2CaSO4·K2SO4, and ß-2CaO·SiO2, the molar ratios of CaO: Al2O3: CaSO4 must be kept at 3:3:1 and that of CaO/SiO2, over 2.0; otherwise, the generated amount of 3CaO·3Al2O3·CaSO4 decreased and that of gehlenite (2CaO·Al2O3·SiO2) with no hydration increased quantitatively. Therefore, if all SO3(g) generated by the thermal decomposition of alunite reacts with CaCO3 (or CaO, the thermal decomposition product of limestone) to form CaSO4 in an alunite- limestone system, 1 mol of pure alunite reacts with 6 mol of limestone to form 1 mol of 3CaO·3Al2O3·CaSO4 and 1 mol of 2CaSO4·K2SO4.

Issn:14248220

Keywords: alunite ; limestone ; calcium sulphoaluminate ; calcium langbeinite

Volume: 9

Pages: 5059-5067

The mitochondrial response to changes of cytosolic calcium concentration has a strong impact on neuronal cell metabolism and viability. We observed that Ca2+ additions to isolated rat brain mitochondria induced in potassium ion containing media a mitochondrial membrane potential depolarization and an accompanying increase ofmitochondrial respiration. These Ca2+ effects can be blocked by iberiotoxin and charybdotoxin, well known inhibitors of large conductance potassium channel (BKCa channel). Furthermore, NS1619 – a BKCa channel opener – induced potassium ion–specific effects on brain mitochondria similar to those induced by Ca2+. These findings suggest the presence of a calcium-activated, large conductance potassium channel (sensitive to charybdotoxin and NS1619), which was confirmed by reconstitution of the mitochondrial inner membrane into planar lipid bilayers. The conductance of the reconstituted channel was 265 pS under gradient (50/450 mM KCl) conditions. Its reversal potential was equal to 50 mV, which proved that the examined channel was cation-selective. We also observed immunoreactivity of anti-b4 subunit (of the BKCa channel) antibodies with ~26 kDa proteins of rat brain mitochondria. Immunohistochemical analysis confirmed the predominant occurrence of b4 subunit in neuronal mitochondria. We hypothesize that the mitochondrial BKCa channel represents a calcium sensor, which can contribute to neuronal signal transduction and survival.

Issn:14220067

Keywords: Mitochondria ; brain ; channel openers ; potassium channel ; iberiotoxin ; NS1619

Volume: 10

Pages: 1104-1120

In order to investigate the physiological effect of transfected cell immobilization in calcium alginate gels, we immobilized electroporated Vero cells in gels shaped either as spherical beads or as thin membrane layers. In addition, we investigated whether serum addition had a positive effect on cell proliferation and viability in either gel configuration. The gels were stored for four weeks in a medium supplemented or not with 20% (v/v) foetal calf serum. Throughout a culture period of four weeks, cell proliferation and cell viability were assayed by optical microscopy after provision of Trypan Blue. Non-elaborate culture conditions (room temperature, non-CO2 enriched culture atmosphere) were applied throughout the experimental period in order to evaluate cell viability under less than optimal storage conditions. Immobilization of electroporated cells was associated with an initially reduced cell viability, which was gradually increased. Immobilization was associated with maintenance of cell growth for the duration of the experimental period, whereas electroporated cells essentially died after a week in suspension culture. Considerable proliferation of immobilized cells was observed in spherical alginate beads. In both gel configurations, addition of serum was associated with increased cell proliferation. The results of the present study could contribute to an improvement of the storability of biosensors based on electroporated, genetically or membrane-engineered cells.

Issn:14248220

Keywords: Calcium alginate ; Cell immobilization ; Electroporation ; Foetal calf serum (FCS) ; Monkey African green kidney (Vero) cells

Volume: 9

Pages: 378-385

The influence of electron and hole scavengers in the photocatalytic digestion of organic matter in the presence of suspended particles of TiO2 was investigated. The process, aiming at the electrochemical determination of traces of heavy metals in water samples, was followed through the recovery of the voltammetric wave of Cd(II) in the presence of EDTA, chosen as model ligand that mimics the complexing effect of natural dissolved organic matter. The accelerating power of O2, acting as electron scavenger, was confirmed. In the absence of O2, a similar function is played by nitrate ions but not, as it seems, by the analyte, Cd(II). On the other hand, CH3OH exhibits an antagonist effect as hole scavenger. This observation may explain why the acetate (from the pH buffer), used to control the medium acidity, leads to a certain reduction in the photocatalytic yield.

Issn:01035053

Keywords: photodigestion ; TiO2 ; scavengers ; voltammetry

Volume: 13

Pages: 441-448

A flow injection system coupled to focused microwave-assisted oven was used for on-line orange juice sample digestion for determination of Ca, Cu, Fe, K, Mg, Mn, Na, P, and Zn by inductively coupled plasma optical emission spectrometry. The reactor coil was a PTFE tube (4.0 m long and 1.6 mm i.d.) positioned into the commercial glass tube of the focused microwave oven. Aliquots of 500 muL of sample and 1000 muL of reagent (80% v/v HNO3) were mixed in a confluence and carried out to the reactor coil by air carrier. The relative standard deviation for five replicates of sample was lower than 5.0%. Good recoveries varying from 91 to 111% were obtained for added concentrations of the interest elements. The results obtained using the proposed digestion system are in agreement with those obtained for total digestion at the 95% confidence level. With this on-line digestion system was possible to carry out 12 samples h-1, minimizing contamination, saving consumption of samples and reagent and low residue generation.

Issn:01035053

Keywords: on-line digestion ; orange juice ; focused microwave oven ; atomic emission

Volume: 14

Pages: 435-441

In this paper a simple and rapid acid digestion method by microwave heating in highpressureTeflon-TFM bombs is reported for the determination of total iron and zinc content infodder yeasts, by flame atomic absorption spectrometry (FAAS). The analytical results wereagreed well, as confirmed by the statistical evaluation, with those obtained after conventionalwet digestion method. This procedure was applied to the determination of Fe and Zn in someRomanian fodder yeasts growth on n-paraffines, methanol and ethanol.

Issn:1220871X

Keywords: Fodder yeasts ; microwave digestion ; iron ; zinc ; FAAS

Volume: XIII

Pages: 117-124

In the work, we developed glycidoxypropyltrimethoxysilane (GLYMO)-modified Fe3O4@SiO2 core and perpendicularly aligned mesoporous SiO2 shell (designated Fe3O4@nSiO2@mSiO2) as the novel substrate forthe immobilization of large amount of trypsin and applied it for fast protein digestion.Firstly, Fe3O4@nSiO2@mSiO2 microspheres were synthesized. Then, the surface of the microspheres was functionalized with GLYMO for enzyme immobilization.The amount of trypsin immobilized on Fe3O4@nSiO2@mSiO2 was about 188 ì g/mg, which was much more than that on the previous magnetic materials. Using the trypsin-immobilized magnetic mesoporous SiO2 microspheres, proteins in samples were fast digested with microwave irradiation. The efficacy of this technique for protein mapping was demonstrated by the massspectral analysis of the peptide fragmentation of three standard proteins, including cytochrome c (Cyt-c), myglobin (MYG), and bovine serum albumin (BSA). The functionalized magnetic microspheres served not only as substrate for enzyme immobilization, but also as excellent microwave absorbers, thus greatly improved the efficiency of protein digestion. It is also worth noting that by using this novel approach, the protein can be effectively digested within seconds, in contrast to hours required by conventional methods. Moreover, the trypsin-immobilized magnetic mesoporous SiO2 microspheres exhibit better stability than conventional methods. Furthermore, the feasibility of using this novel strategy for real sample analysis was demonstrated by applying it to the analysis of human pituitary extraction which opens a route for its further application in large-scale proteomic analysis.

Issn:0974276X

Keywords: Mesoporous SiO2 microspheres ; Peptide mapping analysis ; Microwave-assisted digestion ; MALDI-TOF MS

Volume: 01

Pages: 346-358

Human plasmacytoid dendritic cells secrete high levels of IFNa and are thus implicated in the activation of NK cells. Activated NK cells are characterised by the up-regulation of CD69 and MHC class II DR expression, secretion of IFN g and enhanced cytotoxicity. We show that pDC mediate these processes by different mechanisms, some of which overlap. Human NK cells were analysed after co-culture with immature or CpG-matured blood pDC or with supernatant from these cells. Maximal CD69 expression by NK cells was mediated by supernatant from mature pDC and did not require pDC contact. Up-regulation was due in part to IFNa but also to factors in IFNa negative supernatant from immature DC. HLA-DR expression was independent of secreted molecules but required contact with immature or mature DC. Enhanced NK cytotoxicity, measured by killing of K562 targets and expression of CD107a, was mediated by multiple factors including type I IFN, supernatant from immature pDC cultures and contact with immature or mature pDC. These factors act cumulatively to enhance cytotoxcity. Thus different parameters of pDC mediated NK cell activation are regulated by distinct pathways.

Issn:14248220

Keywords: dendritic cells ; NK cells ; cytokines ; cytotoxicity

Volume: 9

Pages: 386-403

Several extracts of aerial parts of Leonotis nepetaefolia showed anti-inflammatory activity on TPA-induced edema model. The chromatography of the extracts led to the isolation of stigmasterol and leonotinin. Although the presence of leonotinin is in agreement with previous phytochemical studies of this species, this is the first time that its anti-inflammatory activity is determined.

Issn:05837693

Keywords: Leonotis nepetaefolia ; leonotinin ; stigmasterol ; diterpenes ; labdanes ; anti-inflammatory activity.

Volume: 48

Pages: 293-295