Activation Energy for Permeation of Phosphonium Cations through Phospholipid Bilayer Membrane

Atsushi Ono, Seiji Miyauchi, Naoki Kamo, Makoto Demura, Tetsuo Asakura

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The conductance caused by translocation of various phosphonium cations across phospholipid (from soybean) bilayer membrane was measured. Phosphonium cations used were tetraphenylphosphonium (TPP+) and triphenylalkylphosphonium cations formulated as (Phe)3−P+-(CH2)nCH3 (n = 0–5). The conductance was dependent on voltage applied externally to the membrane in accordance with a theory developed by previous authors. Using the theory, values of βki were determined, where β and ki are a linear partition coefficient and a rate constant of transmembrane ion transport, respectively. Since βki depended on the phosphonium ion concentration, values extrapolated to infinite dilution, (βki)0, were determined. Temperature dependence of (βki)0 allowed us to estimate the activation energy of transport, Ea. For TPP+, thermodynamic values obtained were consistent with values calculated by Flewelling and Hubbell [(1986) Biophys. J. 49, 541–552]. When (Phe)3−P+-(CH2)nCH3 (n = 0–5) were used, Ea depended on the odd or even of n. This “odd and even” pattern was observed in a variety of phenomena such as solubility in water, equivalent ionic conductivity in water, and 31P NMR chemical shift.

Original languageEnglish
Pages (from-to)4312-4318
Number of pages7
Issue number14
Publication statusPublished - Apr 1 1994
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry


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