Surface charge density estimation by 9-aminoacridine fluorescence titration: improvements and limitations |
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Authors: | Alajos Bérczi Ian M Møller |
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Institution: | (1) Hungarian Academy of Sciences, Institute of Biophysics, Biological Research Center, P.O.B. 521, H-6701 Szeged, Hungary;(2) Department of Plant Physiology, University of Lund, P.O.B. 7007, S-22007 Lund, Sweden |
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Abstract: | A large number of surface charge density () and surface potential (o) estimations have been based on 1) titrations of the fluorescence of 9-aminoacridine released from the diffuse double layer adjacent to negatively charged membrane surfaces by non-adsorbing monovalent and divalent cations, and 2) calculations using experimental data from the titration curves and the Gouy-Chapman theory of the diffuse double layer. In this paper we discuss the different simplifying approximations employed in the earlier calculations and recommend modified formulas for the calculations. The latter have been derived without any simplifying approximation concerning the ionic (electrolyte) composition of the titration assays. We also show that depends, to some extent, on the concentrations of buffer and vesicles in the assays and present experimental evidence that decamethonium (decane-1,10-bis-trimethylammonium), a bulky organic divalent cation, can be satisfactorily used for the estimation of under well-defined conditions, despite its putative interaction with membranes.Abbreviations 9-AA
9-aminoacridine
- (DeM)2+
decamethonium
- (DiM)2+
dimethonium
- EDTA
ethylenediaminetetraacetic acid
- EGTA
ethylene glyol-bis(-aminoethyl ether) N,N,N,N-tetraacetic acid
- (HeM)2+
hexamethonium
- MES
2-(N-morpholino) ethanesulfonic acid
- MOPS
4-morpholinopropanesulfonic acid
- PM
plasma membrane
- Tris
tris(hydroxymethyl)aminomethane
-
surface charge density
- o
surface potential
Correspondence to: A. Bérczi |
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Keywords: | 9-aminoacridine Fluorescence Membrane vesicles Surface charge density Surface potential |
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