Date(s) - 03/08/2010
5:00 pm - 6:00 pm
Direct electron transfer is a highly distance-dependent, voltage-dependent process that is essential for key biological processes such as photosynthesis, respiration, and neutralization of reactive oxygen species (ROS). The physical chemistry of direct electron transfer in redox enzyme-protein systems has been the focus of intensive investigations for over twenty years, and has led to increased understanding of how protein structure determines redox potential. This new information, along with emerging nanotechnologies, allows for the rational design of materials and proteins for controlled electron transfer with biomolecules. In this presentation, I show two examples of designed electron transfer processes and their potential uses for basic science, environmental engineering, and medicine.
The first example is the use of conjugated semiconductor nanoparticles (quantum dots or QDs) for targeted toxicity in cancer cells and pathogenic bacteria. Any molecule capable of transferring electrons to QDs can be used as a photosensitizing agent, creating a charge-separated state that leads to the production of singlet oxygen and hydroxyl radicals. Many simple, common molecules with high solubility, low toxicity to healthy cells, and targeted distribution in tumors have this property, allowing for rational design of a large number of possible agents. The electron transfer suppresses the QD fluorescence, creating a visible signal of action.
Second, I discuss how fluorescent proteins might be used as components of bioelectronic devices. Electron-transfer processes between a donor, sensitizer (the fluorescent protein) and acceptor may be carefully tailored to produce the most efficient current generation, or to make the current sensitive to environmental conditions. Two specific applications are discussed: light harvesting for alternative energy applications, and development of voltage sensors for optical recording from excitable cells.