Abstract
Zeta potential and dipole potential measures are direct operational methodologies to determine the adsorption, insertion and penetration of ions, amphipathic and neutral compounds into the membranes of cells and model systems. From these results, the contribution of charged and dipole groups can be deduced. However, although each method may give apparent affinity or binding constants, care should be taken to interpret them in terms of physical meaning because they are not independent properties. On the base of a recent model in which the lipid bilayer is considered as composed by two interphase regions at each side of the hydrocarbon core, this review describes how dipole potential and zeta potential are correlated due to water reorganization. From this analysis, considering that in a cell the interphase region the membrane extends to the cell interior or overlaps with the interphase region of another supramolecular structure, the correlation of dipole and electrostatic forces can be taken as responsible of the propagation of perturbations between membrane and cytoplasm and vice versa. Thus, this picture gives the membrane a responsive character in addition to that of a selective permeability barrier when integrated to a complex system.
Highlights
CIBAAL), National University of Santiago del Estero and CONICET, Santiago del Estero 4206, Argentina; Abstract: Zeta potential and dipole potential measures are direct operational methodologies to determine the adsorption, insertion and penetration of ions, amphipathic and neutral compounds into the membranes of cells and model systems
The hydration of the lipids is determinant for the thermodynamic stability and structural dynamics and are a clue to understand the response of the membrane to environmental changes and biologically relevant bio-effectors
Zeta potential measurements provide direct evidence of amino acid orientation in a lipid interphase giving consistency to the findings suggested by molecular dynamics (MD) and surface spectroscopic studies, congruent with the proposal that the guanidine group is buried in the membrane in a water environment [28]
Summary
When dry lipids such as phosphatidylcholines are dispersed in water to form bilayers enclosing an aqueous media or spread on the air–water surface to form monolayers, they interact strongly with water. For details see text [8,9,10,11] This model can be sustained in terms of the formalism of Thermodynamics of IrreThus, if properties of the interphase region of lipid and cell membranes lays on the versible the membrane is functional consideredresponse, as an open with respect specific Processes, properties in of which water and its role in its thesystem electrical properties to water exchange. This exchange determines the mechanical changes due to osmotic exderived from the distribution of charges and dipoles in the polar region of Figure 1 should pansion and contraction [2]. An insight on the correlation between the different potentials will be discussed in order to explore cooperative and synergistic phenomena which are the essence of the membrane responsiveness
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