INTERACTIONS OF CALCIUM-IONS WITH PHOSPHOLIPID-MEMBRANES - STUDIES ON PI-A ISOTHERMS AND ELECTROCHEMICAL AND QUARTZ-CRYSTAL MICROBALANCE MEASUREMENTS

被引:32
作者
EBARA, Y [1 ]
EBATO, H [1 ]
ARIGA, K [1 ]
OKAHATA, Y [1 ]
机构
[1] TOKYO INST TECHNOL,DEPT BIOMOLEC ENGN,MIDORI KU,YOKOHAMA,KANAGAWA 227,JAPAN
关键词
D O I
10.1021/la00019a040
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Interactions of calcium ions with a monolayer of synthetic phospholipid 1,3-dihexadecylglycero-2-phosphoethanolamine (2C16PE) were investigated with three different methods: surface-pressure (pi-A) isotherms, electrochemical reactions on an electrode, and quartz-crystal microbalance (QCM) measurements. pi-A isotherms showed that the 2C16PE monolayer exists with the most condensed molecular packing at pH 5.8 probably due to intermolecular zwitterionic interactions. Ca2+ ions destroy this interaction and expand the monolayer packing. This behavior can be examined on a bilayer-covered SnO2 electrode in electrochemical methods. Oxidation peak currents of a maker ion (Fe(CN)6(3/4-)) in the aqueous phase through the lipid films were increased by the addition of Ca2+ ions only when the membrane was in a bilayer and in the fluid liquid crystalline state above the T(c). The binding behavior of Ca2+ ions onto the 2C16PE LB films was followed directly from the frequency changes of the LB film-deposited QCM. Ca2+ ions can penetrate into the fluid liquid crystalline LB films, but not into the solid films. From these findings, Ca2+ ions can bind and penetrate into only the fluid liquid crystalline state of a bilayer and disturb or expand the membrane structures.
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页码:2267 / 2271
页数:5
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