Events Calendar

Environmental Photochemistry of a-Ketocarboxylic Acids

Speaker: Marcelo I. Guzman, Ph.D., Origins Postdoctoral Fellow - Environmental Chemistry Group, School of Engineering and Applied Sciences, Harvard UniversityAbstract: The reductive tricarboxylic acid (rTCA) cycle has been proposed as a candidate mechanism for carbon fixation and energy storage at the time life originated. An intriguing search is for a chemical pathway to start the rTCA cycle from inorganic precursor compounds. In this seminar, the reaction of CO2 with a-ketocarboxylic acids in order to produce metabolites of the rTCA cycle will be presented. The reactions are promoted by irradiated zinc sulfide (200 to 400 nm light) that serves as a model system for colloidal mineral semiconductors present on early Earth. The results describe a plausible production scheme on early Earth for the compounds of the rTCA cycle (i.e., through a series of non-enzymatic cascading reactions starting from CO2).A second focus of the presentation will be on the direct photochemistry of pyruvic acid, a representative a-ketocarboxylic acids present in tropospheric aerosol. Model organic aerosol matter is produced via photoinduced and thermal reactions. The low volatility products have optical and structural properties reminiscent of environmental aerosol samples. The studies aim to understand the daily cycles of aerosol absorption observed in the field, and that may introduce a key feedback in the Earth's radiative balance.

Location: Kaprielian Hall (KAP) - 209 (On Webex. Call for more information)

Audiences: Everyone Is Invited

Contact: Evangeline Reyes