Electrochemical Study of Ion Transfer of Acetylcholine Across the Interface of Water and a Lipid-Modified 1,2-Dichloroethane

Abstract

The ion transfer of acetylcholine (AcH + ) ions across the unmodified and phospholipid-modified water|1,2-dichloroethane (DCE) interface has been studied by means of square-wave and cyclic voltammetry, as well as by electrochemical impedance spectroscopy. After being transferred in the organic phase, the AcH + ions undergo chemical reactions with the phospholipids. The overall behavior of the experimental system studied in the presence of phospholipids has been compared with the theoretical results of an ECrev reaction. The kinetic parameters of the chemical interactions between AcH + and the phospholipids have been determined from the voltammetric and impedance measurements. Additional characterization of those interactions has been made by using the surface tension measurements.

Coupling of Cyclic Voltammetry and Electrochemical Impedance Spectroscopy for Probing the Thermodynamics of Facilitated Ion Transfer Reactions Exhibiting Chemical Kinetic Hindrances

“…The solutions of the differential equations (1)(2)(3), under the relevant boundary conditions, have been obtained by using the Laplace's transformations, combined with the numerical integration methodology. 20 The solutions for the concentrations of c(M (w) ) x)0 and c(M (o) ) x)0 are identical with those obtained for an EC rev diffusion reaction of the type …”

“…The main reason for this anomalous behavior of such systems is the simultaneous effect on the kinetics (via chemical kinetic parameter ) and thermodynamics (via K) by the ligand concentration. 20,22,34,35 Both phenomena shift the mid-peak potential by about the same values but in opposite directions. The outcome of this is the absence of the mid-peak potential shifting at the cyclic voltammograms.…”

“…If this holds true, then the facilitated ion transfer processes can be thought to take place according to an EC mechanism, where the ion transfer is the electrochemical (E) step, and the consecutive complexation of the ion by the ionophore is a chemical step (C). 5,6,20,21 It is worth mentioning that, beside this EC consideration, cases exist where the CE mechanism is also proposed as an adequate model for describing the facilitated ion transfer reactions. 21 In that case, usually the ligand (ionophore) is partitioned from the organic in the water phase, while forming there a charged complex with the metal ions (C step).…”

Evaluation of the lipophilic properties of opioids, amphetamine-like drugs, and metabolites through electrochemical studies at the interface between two immiscible solutions

“…In addition, a more comprehensive study currently being developed will consider the modification of the liquidjliquid interface with phospholipids [32], mimicking in that way the double-layer living cell membranes.…”

“…However, n-octanol cannot be used as an organic medium for assessing the lipophilicity data of ions by voltammetry at the ITIES due to the nonpolarizable nature of the interface with water [1][2][3][4][5]. This methodology has been applied to the study of cation transfer using DCE as solvent, which usually is noted as a good alternative for n-octanol [3][4][5][30][31][32][33], although both solvents have a different nature. A schematic representation of the electrochemical cell used in the current work is depicted in Fig.…”