Temperature-jump method for studying the fast transport of Na+ by (221) C10-cryptand across lipid membranes.
Biophys Chem
; 41(2): 203-15, 1991 Nov.
Article
em En
| MEDLINE
| ID: mdl-1663399
ABSTRACT
The kinetics of Na+ transport by (221)C10-cryptand through thin lipid membranes were determined by performing temperature-jump relaxation experiments on large unilamellar vesicles (L.U.V.) loaded with a fluorescent pH indicator. Applying temperature jumps of 4 to 7 degrees C to liposomes having phosphate as internal buffer and Tris as external buffer resulted in transmembrane delta pH's of about 0.104 to 0.182. After a temperature-jump, a decay in the delta pH was observed which corresponded to a Na+/H+ exchange occurring through membranes in the simultaneous presence of the cryptand and a proton carrier. The transport of Na+ ions by (221)C10 was found to be a fast kinetic process. Its initial rate increased with both the temperature and the cryptand concentrations. In addition, the temperature-induced changes in the apparent rate constants of the translocation of Na+ by (221)C10 were carrier concentration-dependent, and the apparent activation energy required to activate the transport decreased significantly with increasing cryptand concentrations. The results are discussed in terms of the structural, physico-chemical and electrical characteristics of carriers and complexes.
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Base de dados:
MEDLINE
Assunto principal:
Sódio
/
Lipossomos
/
Lipídeos de Membrana
Tipo de estudo:
Prognostic_studies
Idioma:
En
Ano de publicação:
1991
Tipo de documento:
Article