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1.
Colloids Surf B Biointerfaces ; 61(1): 10-6, 2008 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-17869071

RESUMO

In the present work, Pb(II) and Cd(II) ion adsorption onto inert organic matter (IOM) obtained from ground dried plants: Euphorbia echinus, Launea arborescens, Senecio anthophorbium growing in semi-arid zones of Morocco and Carpobrotus edulis as the Mediterranean plant has been studied. A suspension of plant deroed micro-particles adsorbs lead and cadmium present as ionic species, with a higher affinity for Pb(II). The kinetics and the maximum capacity adsorption depend on the type of plant as well as on the metal ions (atomic weight, ionic radius and electronegativity). The adsorption process is affected by various parameters such as contact time, solution volume to mass of plant particles ratio (m/V), particle size, solution pH and metal concentration. A dose of 25 g/l of adsorbent was optimal to obtain maximum adsorption of both metal ions. The maximum metal uptake was obtained with particles of organic matter of <50 microm. As to classical ionic adsorption phenomena, the adsorption of both metal ions increases with the increase of the initial concentration in the solution. For the two metal cations, the uptake efficiency of the studied plants ranged from: C. edulis>E. echinus>S. anthophorbium>L. arborescens, however, the differences are rather small. Two different waste water types (domestic and industrial) were tested and good results were obtained for removal of Pb(II) and Cd(II) at more than 90%. The removal of the metal and mineral ions waste water was observed for PO(4)(3-) at 88%, for NO(3)(-) at 96.5% and for metal ions (Pb(II), Cd(II), Cu(II) and Zn(II)) at about 100%, using IOM as absorbent.


Assuntos
Cádmio/isolamento & purificação , Chumbo/isolamento & purificação , Purificação da Água/métodos , Adsorção , Asteraceae , Caryophyllaceae , Cátions Bivalentes/isolamento & purificação , Dessecação , Euphorbia , Concentração de Íons de Hidrogênio , Tamanho da Partícula , Senécio , Eliminação de Resíduos Líquidos , Poluentes Químicos da Água/isolamento & purificação
2.
Sci Total Environ ; 349(1-3): 56-66, 2005 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-16198669

RESUMO

Electrokinetic extraction has been tested to remove lead from an Algerian contaminated soil ([Pb] = 4.432 +/- 0.275 mg g(-1)) sited near a battery plant. The effect of EDTA at various concentrations (0.05-0.20 M) on the enhancement of lead transport has been studied by applying a constant voltage corresponding to a nominal electric field strength of 1 V cm(-1) (duration: 240 h). Results of contaminant distribution across the experimental cell have shown efficient transport of lead toward the anode despite the presence of calcite (25%) and the high acid/base buffer capacity of the soil. To avoid ligand loss, which would be anodically oxidized, the cell was modified by adding extra compartments and inserting cation exchange membranes (Neosepta CMX). Thus, simultaneous recovery of EDTA and lead from their chelated solutions has been made possible using the same set-up and by controlling fluids chemistry.


Assuntos
Quelantes/química , Ácido Edético/química , Chumbo/isolamento & purificação , Poluentes do Solo/isolamento & purificação , Gerenciamento de Resíduos/métodos , Resinas de Troca de Cátion , Quelantes/isolamento & purificação , Ácido Edético/isolamento & purificação , Eletroquímica , Resíduos Industriais , Cinética , Chumbo/química , Solo/análise
3.
Chemphyschem ; 2(2): 109-14, 2001 Feb 16.
Artigo em Inglês | MEDLINE | ID: mdl-23696436

RESUMO

The particular chromophoric structure of C(70)Ph(10), which consists of two cage-centered π-electron systems, makes its photophysical properties an exception to those found for other phenylated [70]fullerenes C(70)Ph(2n) (n=2-4). For these other C(70)Ph(2n) species, their intrinsic photophysical properties undergo smooth transitions as a function of n.


Assuntos
Fulerenos/química , Teoria Quântica , Benzeno/química , Espectrofotometria Ultravioleta , Estereoisomerismo
4.
J Colloid Interface Sci ; 218(2): 377-387, 1999 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-10502369

RESUMO

Carboxylic true ionophores were previously demonstrated to have efficient antimalarial activity against the human parasite Plasmodium falciparum, with a 50% inhibitory concentration around nM and generally high selectivity as compared to their toxic effects against mammalian cell lines. The decreased molecular packing of the erythrocyte membrane outer leaflet after malarial infection could explain the preferential ionophore interaction with infected erythrocytes. Monolayer penetration experiments using different phospholipid films showed strong incorporation of true carboxylic ionophores, from classes 1 (nigericin) and 2 (lasalocid), up to a surface pressure close to film collapse. The interaction was slightly higher with PC (phosphatidylcholine) monolayers than with monolayers composed of cholesterol-containing total lipid extracts from either malaria-infected or normal erythrocytes, and the two latter induced identical interactions with 5-bromo lasalocid. Surface pressure-area isotherms for pure ionophores on water and surface tension of ionophore aqueous solutions clearly highlighted the surface-active characteristics of these ionophores and allowed determination of their molecular area in compact monolayers. The estimated ionophore concentration in the mixed interfacial layers indicates that higher amounts (threefold more) of ionophores might be integrated in infected erythrocyte membrane due to their impaired molecular packing as compared to normal erythrocytes. This infection-enhanced penetration efficiency does not appear directly related to the change in erythrocyte membrane lipid composition, but it could be the basis of ionophore selectivity for infected erythrocytes. Copyright 1999 Academic Press.

5.
Bioorg Med Chem ; 2(3): 181-5, 1994 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-7922130

RESUMO

Bilirubin, biliverdin and their serum albumin complexes were tested as oxyradical scavengers (superoxide generated by the xanthine/xanthine oxidase system and peroxyl radical-trapping antioxidant ability). As superoxide scavengers the free bile pigments showed activities near to that of serum albumin, higher than the water soluble vitamin E analog Trolox and lower than ascorbic acid. The peroxyl radical-trapping antioxidant abilities of the tested bile pigments were much higher than those of the serum albumin and of the same order as their serum albumin complexes. This interaction with peroxyl radicals showed different stoichiometric factors for bilirubin (approximately 2) and biliverdin (approximately 4).


Assuntos
Antioxidantes/farmacologia , Pigmentos Biliares/farmacologia , Animais , Antioxidantes/química , Pigmentos Biliares/química , Bilirrubina/química , Bilirrubina/farmacologia , Biliverdina/química , Biliverdina/farmacologia , Bovinos , Sequestradores de Radicais Livres , Humanos , Técnicas In Vitro , Oxirredução , Albumina Sérica/química , Superóxidos/química
6.
Photochem Photobiol ; 54(1): 123-6, 1991 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-1946689

RESUMO

Under light excitation transmembrane electron transfer is observed when a stacked Zn-Cu-Zn triporphyrin is incorporated in a bilayer between aqueous redox phases. The electric polarization of the membrane due to the photoinduced transmembrane charge flux drives ion transport. This effect increases the net charge transfer across the system, giving rise to an amplification similar to a field effect transistor. Thus this system can be considered an organic phototransistor.


Assuntos
Bicamadas Lipídicas , Metaloporfirinas/química , Radiossensibilizantes/química , Transporte de Elétrons , Potenciais da Membrana , Modelos Biológicos , Oxirredução , Fotoquímica
7.
Chem Biol Interact ; 48(1): 91-101, 1984 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-6229346

RESUMO

The use of bimolecular lipid membranes (BLM) as model membrane allows the analysis of the transport of mercury compounds across the lipidic barriers of biological membranes. The results of flux measurements show that two mercury compounds--HgCl2 and CH3HgCl--cross the BLM but the overall permeabilities are dependent on the pH of the aqueous media, and are not apparently influenced by the different phospholipid constituents of the bilayers. On the other hand, electrical measurements show that, function of the chemical speciation, the transport of this metal is done essentially in the neutral form.


Assuntos
Cloretos/metabolismo , Bicamadas Lipídicas/metabolismo , Lipídeos de Membrana/metabolismo , Mercúrio/metabolismo , Compostos de Metilmercúrio/metabolismo , Transporte Biológico/efeitos dos fármacos , Concentração de Íons de Hidrogênio , Cloreto de Mercúrio
8.
Eur J Biochem ; 133(3): 689-95, 1983 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-6861750

RESUMO

Proteolipid apoproteins have been isolated from a whole bovine brain homogenate by chloroform/methanol extraction, and fractionated by chromatography on modified (lipophilic) Sephadex, followed by ion-exchange chromatography on CM-Trisacryl. The various final, highly hydrophobic, fractions are homogeneous (sodium dodecyl sulfate/polyacrylamide gel electrophoresis). Transmembrane ion transfers were studied by 22Na + flux and electrical conductance measurements. Single channel events were observed at low protein concentrations, in particular with one of the final homogeneous apoproteolipids of molecular mass 24 kDa.


Assuntos
Química Encefálica , Permeabilidade da Membrana Celular , Lipídeos de Membrana/isolamento & purificação , Proteolipídeos/isolamento & purificação , Aminoácidos/isolamento & purificação , Animais , Bovinos , Fenômenos Químicos , Química , Eletroforese em Gel de Poliacrilamida , Lipídeos de Membrana/fisiologia , Proteolipídeos/fisiologia
9.
Biochem Biophys Res Commun ; 113(3): 765-71, 1983 Jun 29.
Artigo em Inglês | MEDLINE | ID: mdl-6870888

RESUMO

Voltage jump studies of planar bilayers doped with colicin A revealed two classes of time and voltage dependent conductance induced by colicin A. The first type of conductance, asymmetrically voltage dependent, measured as a time dependent process, was in agreement with previously described conductances of bilayers doped with colicin A or colicin E1. The second class of conductance appeared as a voltage dependent instantaneous conductance. The significance of this new type of conductance is discussed.


Assuntos
Colicinas , Bicamadas Lipídicas , Condutividade Elétrica , Eletroquímica , Fatores de Tempo
11.
Biochim Biophys Acta ; 591(1): 37-52, 1980 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-7388016

RESUMO

The photo response of bacteriorhodopsin adsorbed on a bimolecular lipid membrane has been investigated using short-circuit current measurements. The results revealed a biphasic current vs. time curve for the photocurrent at pH values of approx. 7. This phenomenon could be modified by altering either the value of the external applied electrical field or the proton concentration differences. The observed effects of the external applied voltage, pH gradient and lipophilic proton carriers enabled us to conclude that the bacteriorhodopsin can be adsorbed in two different states, which give rise to a pumping effect and a flux of protons in opposite directions. A theoretical analysis of the photocycle in relation to the electrical field which acts on the proton uptake and release is proposed. The main effect of this field is to diminish the pumping rate due to the proton motive force resulting from the creation of space-charge in the vicinity of purple membrane fragments.


Assuntos
Bacteriorodopsinas , Carotenoides , Bicamadas Lipídicas , Bacteriorodopsinas/fisiologia , Carbonil Cianeto m-Clorofenil Hidrazona , Carotenoides/fisiologia , Estimulação Elétrica , Halobacterium , Concentração de Íons de Hidrogênio , Fosfatidilcolinas , Fotoquímica
12.
Biochim Biophys Acta ; 511(3): 499-508, 1978 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-28761

RESUMO

The influence of the pH on the stability and stoichiometry of the complexes formed by carboxylic-antibiotics such as grisorixin, alborixin and monensin with alkaline and alkaline earth cations has been investigated. The maximum values of bimolecular lipid membrane conductance are obtained with grisorixin and potassium ion. The conductance-pH curves show a very pronounced maximum in the neutral pH range. The results are analysed on the basis of a dimeric form of the ionophore in the complex and the possibility of having several charged complexes resulting from an heterogeneous reaction, the number of each complexed form depending on the pH of the bulk solutions.


Assuntos
Antibacterianos , Cátions , Furanos , Lipídeos , Membranas Artificiais , Monensin , Nigericina , Antibacterianos/análogos & derivados , Cálcio , Césio , Fenômenos Químicos , Físico-Química , Condutividade Elétrica , Concentração de Íons de Hidrogênio , Ionóforos , Lítio , Nigericina/análogos & derivados , Potássio , Piranos , Sódio
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