Goals and objectives: many forms of energy transduction on early earth have been suggested, perhaps most popularly geothermal and electrical synthesis of organic molecules. However, solar energy was…

This is a grant awarded by the National Aeronautics and Space Administration (NASA) to the Connecticut State University System for research on early Earth energy transduction and carbon fixation using polycyclic aromatic hydrocarbons (PAHs). The goal is to investigate whether a simple form of photosynthesis using PAHs could have produced reduced carbon from carbon dioxide prior to the emergence of life. The $187,388.69 grant supports the development of a proto-cell model with fatty acid membranes and PAHs, and experiments to monitor carbon conversion and proton gradient formation when exposed to light. This research aims to enhance understanding of prebiotic energy transduction processes that could have facilitated abiogenesis, and to inform the search for life elsewhere in the universe. The award does not have a set-aside designation.

Goals and objectives: many forms of energy transduction on early earth have been suggested, perhaps most popularly geothermal and electrical synthesis of organic molecules. However, solar energy was likely more abundant and ubiquitous in surface environments, due to the lack of an ozone layer. Additionally, the availability of photoactive compounds, including polycyclic aromatic hydrocarbons (pahs), is evidenced by their presence in carbonaceous meteorites. We propose that an early form of photosynthesis using pahs would have produced reduced carbon from carbon dioxide, by coupling photo-excitation to transmembrane electron transport and the generation of a proton gradient. If successful, this will represent a simple way to generate usable carbon within a cell, and will further our understanding of proto-biological chemical systems that could have preceded the first living organisms. Approach and methodology the first step is to generate a proto-cell composed of single chain amphiphiles, such as fatty acids, which are considered prebiotic, along with the photosensitizing pahs. Pahs have been shown to spontaneously insert into fatty acid membranes and enhance stability. Carbon dioxide will be used to generate an oxygen free atmosphere, and act as a reactant. Because IT is non-polar, CO2 can easily diffuse through the cell membrane. Lastly, an external electron donor will be added, such as dithiothreitol, less odorous mimic of hydrogen sulfide or other early earth reductants. The proto-cellular construct will be exposed to light, where the CO2 will be converted into organic carbon, likely formate, and be trapped inside of the negatively charged membrane. The interior of these cells can also be loaded with a PH-sensitive DYE to monitor proton gradient formation. The cells will then be separated from the external products using size exclusion chromatography, and the encapsulated products will be evaluated using gas and/or liquid chromatography, and detected with either mass spectrometry, flame ionization, or as charged aerosols. Additionally, changes in both the amphiphiles and pahs can be monitored with these methods. This approach distinguishes itself from other photochemical studies by coupling the following properties: 1) modeling an early earth environment; 2) using simple amphiphiles as opposed to phospholipids; 3) generating usable carbon for the protocelli. If successful, future work will include conversion of products into larger carbon molecules, like amino acids, or sugars. Scope within exobiology this research will enhance our understanding of prebiotic energy transduction including possible molecular processes and chemical conditions that would have promoted abiogenesis. The model proposed is based on experimental and theoretical models of earth prior to the formation of life. Additionally, this study will provide a model for early forms of photosynthesis and experimentally investigate its applications and limitations. The conclusions of this research will also contribute to the search for life elsewhere in the universe by demonstrating alternatives to earth s current bioenergetics.