Distinguished Professor and Chair Department of Chemistry and Biochemistry University of California, San Diego
Surface and Multiphase Chemistry and Photochemistry of Pyruvate
The Grassian group’s research focuses on the chemistry and impacts of environmental interfaces. Current projects in in her lab includes studies of atmospheric aerosol chemistry, geochemical interfaces, nanomaterials in the environment and indoor surface chemistry.
Pyruvate, the deprotonated form of pyruvic acid, serves as an intermediate for both aerobic and anaerobic metabolism and has been proposed to be a promising prebiotic molecule initializing primitive metabolism. This talk will focus on some recent studies of the chemistry and photochemistry of pyruvate, as well as its protonated form, on oxide surfaces (SiO2, Al2O3 and TiO2) and in high ionic strength aqueous environments relevant to sea spray and the sea surface microlayer. Most interesting is the formation of several new compounds detected with mass spectrometry following extraction from two of the oxide surfaces – Al2O3 and TiO2. These compounds include zymonic acid, which is found to be present under both dark and light conditions, and other higher molar mass oligomeric species such as parapyruvic acid, acetolactic acid, and 2,4-dihydroxy-2-methyl-5-oxohexanoic acid (DMOHA) that form only under irradiation. Although this study shows that there are some parallels between aqueous phase photochemistry of pyruvic acid and the photochemistry of adsorbed pyruvic acid in terms of the products that form, there are also distinct differences with several other new photoproducts observed on these two reactive oxide surfaces including lactic acid dimers and trimers as well as a significant amount of even larger oligomeric species not seen in the aqueous phase chemistry. Because of the role of pyruvic acid, the simplest of the alpha-keto acids, in the atmosphere and in metabolic pathways, these results have implications to the chemistry that occurs in both indoor and outdoor environments and during prebiotic Earth conditions.