Interfacial ionization and partitioning of membrane-bound local anaesthetics

Jinsei Miyazaki, Kálmán Hideg, Derek Marsh

Research output: Article

86 Citations (Scopus)


Consideration of the interfacial protonation equilibria of membrane-associated amphiphiles indicates that the partition coefficients of the protonated and unprotonated species will differe considerably. The partition coefficients of the charged and uncharged forms of spin-labelled myristic acid in dimyristoylphosphatidylcholine bilayer dispersions have been measured by EPR spectroscopy and found to be approximately 140-fold higher for the protonated acid than for the dissociated salt form. This ratio of partition coefficients is found to be in good agreement with that predicted from the interfacial shift in pKa of the fatty acid on its partitioning into the membrane. The latter was determined from the changes in the EPR spectra of the membrane-associated fatty acid with pH and was found to be +2.1 pH units. The interfacial shifts in pKa for a series of spin-labelled analogues of tertiary amine local anaesthetics have been determined from the pH dependence of the partition coefficients in dimyristoylphosphatidylcholine bilayer dispersions and are found mostly to be in the range of approx. -1.0 to -1.5 pH units, corresponding to a 10- to 30-fold higher partition coefficient of the uncharged base compared with that of the charged ammonium form.

Original languageEnglish
Pages (from-to)62-68
Number of pages7
JournalBBA - Biomembranes
Issue number1
Publication statusPublished - jan. 10 1992

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

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