295 Energy Transduction in Vesicles

Thursday, November 5, 2009: 11:20 AM
Ballroom C+D (Camino Real Hotel)
David P. Summers, Ph. D., MIT , Carl Sagan Center, SETI Institute, Moffett Field, CA
Juan Noveron , Department of Chemistry, University of Texas at El Paso, El Paso, TX
Ranor Basa, AA, Foothill College , Dept. of Chemistry, Foothill College, Los Altos, CA
Amphiphilic bilayer membrane structures (vesicles) have been postulated to have been abiotically formed and spontaneously assemble on the prebiotic Earth to provide compartments for early cellular life. These vesicles are similar to modern cellular membranes and can serve to contain water-soluble species, protect against dilution, and have the potential to catalyze reactions. The origin of the use of photochemical energy to drive metabolism (ie. energy transduction) is one of the central issues in our attempts to understand the origin and evolution of life. When did energy transduction and photosynthesis begin? What was the original system for capturing photochemical energy? How simple can such a system be? It has been postulated that vesicle structures developed the ability to capture and transduce light, providing energy for reactions. It has been shown that pH gradients can be photochemically created, but it has been found difficult to couple these to drive chemical reactions.
It is known that colloidal semiconducting mineral particles can drive redox chemistry. We show that encapsulation of these particles has the potential to provide a source of energy transduction inside vesicles, and thereby drive protocellular chemistry and represent a model system for early photosynthesis. TiO2 particles, in size range of ~20 nm, can be incorporated into vesicles and retain their photoactivity through dehydration/rehydration cycles that have been shown to be able concentrate species inside a vesicle.  It is shown that these can be used to produce biochemical species such as NADH in such structures.