The Journal of Membrane Biology

, Volume 65, Issue 1–2, pp 13–17 | Cite as

Ionophore-mediated transmembrane movement of divalent cations in small unilamellar liposomes: An evaluation of the chlortetracycline fluorescence technique and correlations with black lipid membrane studies

  • M. K. Mathew
  • R. Nagaraj
  • P. Balaram
Articles
Received:
Revised:

Summary

Conceptual advances in the field of membrane transport have, in the main, utilized artificial membranes, both planar and vesicular. Systems of biological interest,viz., cells and organelles, resemble vesicles in size and geometry. Methods are, therefore, required to extend the results obtained with planar membranes to liposome systems. In this report we present an analysis of a fluorescence technique, using the divalent cation probe chlortetracycline, in small, unilamellar vesicles, for the study of divalent cation fluxes. An ion carrier (X537 A) and a pore former (alamethicin) have been studied. The rate of rise of fluorescence signal and the transmembrane ion gradient have been related to transmembrane current and potential, respectively. A second power dependence of ion conduction-including the electrically silent portion thereof — on X537 A concentration, has been observed. An exponential dependence of “current” on “transmembrane potential” in the case of alamethicin is also confirmed. Possible errors in the technique are discussed.

Key words

Membrane-transport fluorescence chlortetracycline X537 A alamethicin ionophore liposome 
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Copyright information

© Springer-Verlag New York Inc 1982

Authors and Affiliations

  • M. K. Mathew
    • 1
  • R. Nagaraj
    • 1
  • P. Balaram
    • 1
  1. 1.Molecular Biophysics UnitIndian Institute of ScienceBangaloreIndia

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