title: Ca2+ action on the stability of egg phosphatidylcholine sonicated vesicles during freeze-thaw cycles.
abstract: The stability of unilamellar vesicles during freeze-thaw cycles strongly depends on the Ca2+ concentration in the aqueous solution. Experiments performed at equal ionic strengths with Na+ and Ca2+ solutions indicate that the effect observed is specific for Ca2+. This is interpreted to be a consequence of the adsorption of Ca2+ on the vesicle bilayers. The variation of lipid and Ca2+ concentrations indicates that stability is achieved at a particular Ca2+/lipid ratio of 8 mol/mol above which vesicles are stable. The stability appears to be mainly conferred by the external Ca2+ in both slow and rapid cycles, independent of the ionic vesicle content. However, internal Ca2+ seems to increase the stability according to the F/T cycle rate to some extent in the absence of Ca2+ in the external solution.
authors.affiliation: Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Argentina.
authors.forename: L S
authors.initials: LS
authors.lastname: Bakás
authors.forename: E A
authors.initials: EA
authors.lastname: Disalvo
mesh_terms: D002118:Calcium; D004355:Drug Stability; D005615:Freezing; D066298:In Vitro Techniques; D008081:Liposomes; D010713:Phosphatidylcholines; D012996:Solutions; D013010:Sonication
chemical_list: D008081:Liposomes; D010713:Phosphatidylcholines; D012996:Solutions; D002118:Calcium