Chemo-electrical energy conversion of Adenosine triphosphate in a Biological Ion Transporter
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Chemo-Electrical Energy Conversion of Adenosine Triphosphate in a Biological Ion Transporter Vishnu Baba Sundaresan, Stephen Andrew Sarles, Brian J Goode, and Donald J. Leo Mechanical Engineering, Virginia Tech, 310 Durham Hall, CIMSS, Mechanical Engineering, Virginia Tech, Blacksburg, VA, 24061-0261 ABSTRACT Ion transport across cell membranes happens through protein channels and pumps expending concentration gradients, electrical gradients and energy from chemical reactions. Ion exchange in cell membranes is responsible for nutrient transport from production sites to where they are broken down to release energy. Sucrose transport is vital for growth in higher plants and recent research has led to the discovery of a class of sugar carriers called SUT4. The SUT4 transporter is a low affinity, high capacity proton-sucrose transporter that participates in long distance sucrose transport in higher plants. We demonstrated the possibility to use purified SUT4 transporter proteins – with the genetic code from Arabidopsis thaliana expressed on yeast cells – for fluid transport driven by pH gradient and from exergonic ATP hydrolysis reaction in the presence of ATP-ase enzyme. The SUT4 proteins were reconstituted on a planar bilayer lipid membrane formed from 1-Palmitoyl-2-Oleoyl-sn-Glycero-3-[Phospho-L-Serine] (Sodium Salt) (POPS), 1-Palmitoyl-2-Oleoyl-sn-Glycero- 3-Phosphoethanolamine (POPE) phospholipids on a porous substrate. This article builds upon our previous work to harness energy from the ATP-ase reaction using SUT4 to produce a proton current through SUT4 and demonstrates the technical feasibility to generate electrical current in an external circuit. The results from our characterization experiments on a single cell demonstrate that the power source behaves like a constant current power source with an internal resistance of 10-22 kΩ and produces a peak power of 150 nW. INTRODUCTION Transport of ions and fluid in plant and animal cells is an essential process for cell regulation, signaling and growth. Cell membranes are selectively permeable to ions at specific sites in the membrane called ion channels and pumps. Ion pumps in a living cell expend Adenosine triphosphate (ATP) to transport charged species and neutral molecules across the cell membrane. Ion transport due to ATP hydrolysis, referred to as an active transport process, regulates ion concentration in cell cytoplasm. The ionic gradient established by active ion transport opens ion channels for balancing potentials across the membrane. This article discusses our concept and initial results to build an energy-conversion prototype device – called a ‘BioCell’ – that uses biological ion transport processes to generate electrical energy from a biochemical reaction. ION TRANSPORT MECHANISM – TEMPLATE FOR ENGINEERING Plants have evolved to transport various ions and salts from the soil to different sites in the shoot. The transport of sucrose synthesized from biological processes occurs together with proton transport [1]. Investigation on proton-sucr
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