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Updated: Aug 18, 2026

Immuno-fluorescence Assay of Leptospiral Surface-exposed Proteins
Published on: July 1, 2011
Membrane surface potential of Spiroplasma floricola
1Institut für Medizinische Mikrobiologie, Klinikum der Justus Liebig Universität, Giessen, FRG.
Abstract:
Anionic charges, cytochemically identified as lipid phosphate groups, cover the outer membrane surface of Spiroplasma floricola. They induce a negative membrane surface potential which affects the distribution of ions, including protons. Accordingly, the pH at the interface differs from the bulk pH. By using the fluorescent lipoid pH indicator 4-heptadecyl-7-hydroxycoumarin, the pH at the membrane surface was determined. From the difference of the bulk and the interfacial pH the membrane surface potential of S. floricola was calculated to be phi = -118 mV.
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