CHEMICALLY-MODIFIED FIELD-EFFECT TRANSISTORS - THE EFFECT OF ION-PAIRASSOCIATION ON THE MEMBRANE-POTENTIALS

A theoretical model has been developed which relates physically access ible parameters to the formation of a membrane potential. The descript ion is an extension of a theoretical description presented previously by our group, now including divalent cations and ion-pair association. Simulations of the overall membrane potential reveal several factors that may lead to non-Nernstian response curves. For monovalent and div alent cations a reduction in the slope of the response curve (sub-Nern stian response) should virtually always be expected when ion-pair asso ciation takes place in the membrane. Ion-pair association of divalent cations and sample anions can lead to a super-Nernstian response. A di ffusion potential generally reduces the Nernstian slope of the respons e curve. In addition, several experimental results are described which illustrate and confirm our theoretical model.