Ca2+-induced lateral phase separations in phosphatidic acid-phosphatidylcholine membranes

https://doi.org/10.1016/0005-2736(74)90176-XGet rights and content

Abstract

The effects of Ca2+ on phosphatidic acid-phosphatidylcholine membranes have been studied using phospholipid spin labels. ESR spectra of spin-labeled phosphatidic acid-phosphatidylcholine membranes and phosphatidic acid-spin-labeled phosphatidylcholine membranes are exchange-broadened immediately upon addition of CaCl2. These changes directly and conclusively indicate Ca2+-induced clustering of spin-labeled phosphatidylcholine and aggregation of spin-labeled phosphatidic acid bridged by Ca2+-chelation in the binary phopholipid membranes. In the Ca2+-chelated aggregates, the motions of the alkyl chains of phosphatidic acid are greatly reduced and the lipid molecules are more closely packed. The clusters and aggregates are formed in patches and the sizes are dependent on the fractions. Ba2+ and Sr2+ induce the lateral phase separations to the same extent as Ca2+. Mg2+ is also effective but to a lesser extent. In acid solutions (pH 5.5), the Ca2+-induced lateral phase separations are of slightly lesser extent than in alkaline solution (pH 7.9). These results are compared with those for phosphatidylserine-phosphatidylcholine membranes reported previously and necessary conditions for the lateral phase separations are discussed.

References (16)

  • S. Ohnishi et al.

    Biochem. Biophys. Res. Commun.

    (1973)
  • S.F. Yang
  • D. Papahadjopoulos

    Biochim. Biophys. Acta

    (1968)
  • M.B. Abramson et al.

    J. Biol. Chem.

    (1964)
  • E.J. Shimshick et al.

    Biochem. Biophys. Res. Commun.

    (1973)
  • A.W. Cuthbert

    Calcium and Cellular Function

    (1970)
  • I. Tasaki

    Nerve Excitation: A Macromolecular Approach

    (1968)
  • M.S. Steinberg
There are more references available in the full text version of this article.

Cited by (0)

View full text