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Titolo:
TRANSPORT OF COMPETING NA AND K IONS BY (222)C-10-CRYPTAND, AN IONIZABLE MOBILE CARRIER - EFFECTS OF PH AND TEMPERATURE
Autore:
LOISEAU A; MAX H; RENECORAIL L; CASTAING M;
Indirizzi:
INSERM,U426,BP 416 F-75870 PARIS 18 FRANCE INSERM,U426 F-75870 PARIS 18 FRANCE UNIV PARIS 11,FAC SCI ORSAY,BIOENERGET MEMBRANAIRE LAB F-91405 ORSAY FRANCE
Titolo Testata:
Biochimica et biophysica acta. Biomembranes
fascicolo: 2, volume: 1238, anno: 1995,
pagine: 107 - 117
SICI:
0005-2736(1995)1238:2<107:TOCNAK>2.0.ZU;2-J
Fonte:
ISI
Lingua:
ENG
Soggetto:
LIPID BILAYER-MEMBRANES; MEDIATED TRANSPORT; CRYPTATE COMPLEXES; SODIUM-TRANSPORT; VALINOMYCIN; ALKALI; SELECTIVITY; DEPENDENCE; ACTIVATION; IONOPHORE;
Keywords:
IONIZABLE MOBILE CARRIER; ALKALI CATION TRANSPORT KINETICS; COMPETITIVE TRANSPORT SELECTIVITY; PH; TEMPERATURE; LIPID MEMBRANE;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
44
Recensione:
Indirizzi per estratti:
Citazione:
A. Loiseau et al., "TRANSPORT OF COMPETING NA AND K IONS BY (222)C-10-CRYPTAND, AN IONIZABLE MOBILE CARRIER - EFFECTS OF PH AND TEMPERATURE", Biochimica et biophysica acta. Biomembranes, 1238(2), 1995, pp. 107-117

Abstract

The kinetics of the electroneutral exchange of competing sodium and potassium with protons across the membrane of large unilamellar vesicles (LUV) were determined at two pH values when transport was induced bythe simultaneous presence of (222)C-10-cryptand and FCCP (proton carrier) at various temperatures. The aim of the present work was to quantify the pH-dependent enthalpies of an ionizable mobile carrier affinities for competing alkali cations, and to focus on the effects of pH and temperature on the competitive transport selectivity of the carrier for K+ over Na+ ions. At any given temperature and pH, the apparent pH-dependent affinity of (222)C-10 was higher for K+ than for Na+. The enthalpy of this affinity for K+ was significantly lower than that for Na+, whereas it varied similarly with the pH(Delta H(K-mK(pH)) = 32.8 and 37.0 kJ/mol, and Delta H(K-mNa(pH)) = 47.9 and 52.9 kJ/mol at pH 7.8 and 8.8, respectively). When using a kinetic model, the pH effect on these parameters was discriminated (Delta H(K-mK) = 37.9 kJ/mol and Delta H(K-mNa) = 53.9 kJ/mol). The pH-dependence of the Delta H(K-m(pH) of the cations could therefore theoretically be shown to arise from the temperature-induced changes in the ionization of the buffer dissolved in the aqueous phases and of the amine groups of the binding cavity of the carrier. The K/Na competitive transport selectivity (S-c(K/Na)) of (222)C-10 increased linearly with the K+ concentration. It decreased hyperbolically with increasing concentration of Na+ while being independent of pH at any given temperature. In equimolecular ionic mixtures, S-c(K/Na) varied from 2.2 to 3.0 when temperature rose from 20 degrees C to 35 degrees C (Delta H(S-c(K/Na)) = 15.6 +/- 0.5 kJ/mo]). The results are discussed in terms of the structural, physico-chemical and electrical characteristics of carriers and complexes.

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Documento generato il 20/01/21 alle ore 15:42:12