Influence of Voltage Rate on the Diffusion of Organic Ions Through Bilayer Lipid Membranes

Document Type

Student Presentation

Presentation Date



College of Arts and Sciences


Department of Physics

Faculty Sponsor

Dr. Daniel Fologea


Tetraphenylphosphonium chloride(TPP) and Sodium Tetraphenylborate(TPB) are organic ions that are able to passively move across the membrane down the electrochemical gradient. To further investigate the transport of organic ions through the lipid partition of a membrane, we employed artificial planar bilayer membrane bathed by electrolyte solutions. The bilayer membrane integrity was assessed from capacitance and conductance measurements. Changes in membrane permeability upon organic ion addition were monitored by recording the ionic currents in response to variable voltage ramps. Besides expected changes in membrane permeability we observed that the linearity of the I-V plots is strongly influenced by the rate of the voltage change. This is a good indication that the transmembrane transport is a diffusion limited process. In conclusion, these ions are good experimental models for helping us understand similar ionic transport processes through biological membranes.

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