JLE

Magnesium Research

MENU

Biomimetic study of the Ca 2+-Mg 2+ and K +-Li + antagonism on biologically active sites: new methodology to study potential dependent ion exchange Volume 22, numéro 1, March 2009

Auteurs
Faculty of Material Science and Ceramics, AGH-University of Science and Technology, Cracow, Poland, Center for Process Analytical Chemistry and Sensor Technology (ProSens), c/o Process Chemistry Center of Excellence, Åbo Akademi University, FIN-20500 Turku-Åbo, Finland, Department of Chemistry, University of Warsaw, Warsaw, Poland

Competitive divalent (magnesium and calcium) or monovalent (potassium, lithium and sodium) ion exchange and its influence on a membrane potential formation was studied at biological ligands (BL) such as adenosine triphosphate (ATP), asparagine (Asn) and glutamine (Gln) sites. The sites are dispersed electrochemically in membranes made of the conducting polymers (CPs) – poly(N-methylpyrrole) (PMPy) and poly(pyrrole) (PPy). The membranes are made sensitive to calcium and magnesium or to potassium, sodium and lithium by optimized electrodeposition and soaking procedures supported by the study of membrane topography and morphology. Distinctively different electrochemical responses, i.e. electrical potential transients or currents, are observed in the case of “antagonistic” calcium and magnesium or potassium and sodium/lithium ion pairs. Dissimilarity in the responses is ascribed to a difference between on site vs. bulk concentrations of ions, and is dictated by different transport properties of the ions, as shown by using the Nernst-Planck-Poisson (NPP) model and the diffusion-layer model (DLM). The method described allows inspecting potential-dependent competitive ion-exchange processes at the biologically active sites. It is suggested that this approach could be used as an auxiliary tool in study of potential dependent block in realistic membrane channels, such as Mg block in the N-methyl D-aspartate receptor channel (NMDA).