A Chemical Model for the Prebiotic Origins of Tetrapyrrole Macrocycles

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With this award, the Chemistry of Life Processes Program in the Chemistry Division is funding Dr. Jonathan S. Lindsey from North Carolina State University to probe the formation and possible photochemical properties of tetrapyrrole macrocycles under plausible prebiotic conditions. The formation entails a multistage process beginning with simple acyclic reactants and proceeds through a reactive pyrrole on to porphyrinogens, which upon oxidation yield porphyrins. Combinatorial reactions afford a complex mix of tetrapyrrole macrocycles that spontaneously partition among aqueous and membrane vesicles. A key objective is to understand the scope and robustness of this self-organizing chemistry, particularly where reactions may proceed in parallel. A second theme is to employ quantitative analytical methods that place this rich chemistry on a firm physical basis. The knowledge gained will provide a chemical model for the possible origins and function of a potent set of catalysts (tetrapyrroles) supporting proto-metabolism and proto-photosynthetic processes.The origin of life is an enduring and unmet scientific challenge. Tetrapyrrole macrocycles (e.g., chlorophylls) play a central role in all living organisms and have been proposed to play a central role in the origin of life, yet their prebiotic origin has remained obscure. While the exact origins may never be known, the development of a viable chemical model, bounded by constraints of early earth conditions, could provide insight into the possible origins of tetrapyrrole molecules. The proposed research engages undergraduate and graduate students in scientific research with an inherently interdisciplinary flavor (synthesize starting materials, perform chemical reactions, analyze complex mixtures of chemical compounds, assess the prebiotic implications in coordination with earth sciences considerations). A companion course (Molecular Origins of Life), taught by Professor Lindsey annually for senior undergraduates as well as graduate students, addresses fundamental chemical principles in the context of the fascinating field of prebiotic chemistry.