CPOS Seminar: "Determining How Water Structure in Biologically Inspired Condensates Affect Redox Thermodynamics and Kinetics"
Speaker: Gala Rodriguez, Graduate Student Researcher , Sepunaru Group, Department of Chemistry, UC Santa Barbara
Both biochemical and electrochemical reactions are characterized by tuning microenvironments in confined spaces to control reaction kinetics and thermodynamics such as the active site and electrode double layer. Typical features of microenvironments include ionic concentration, electrolyte identity, local dielectrics, and pH. Electrochemistry is uniquely suited to quantitatively study these complex environments with simple outer-sphere redox probes due to their sensitivity to the aforementioned characteristics. I propose using a well defined redox probe to study coacervates, a liquid-liquid phase separation between two opposingly charged polymers creating an electrostatically rich environment. Coacervates have recently garnered interest due to their capacity to dictate biochemical pathways and accelerate both biological and non biological chemical reactions. While these phenomena have been previously reported, insight into how reactant, transition state, and product energies are altered within the droplet remains an active area of research. In other words: my work focuses on how coacervates alter microenvironments to perform as catalysts akin to primordial enzymes.
The first part of my talk discusses how a mixture of poly-L-lysine and poly-uridylic acid alter the reaction thermodynamics of ferri/ferrocyanide, a well-behaved redox couple that has been proposed to be an essential oxidizing agent in prebiotic Earth. By performing temperature dependent electrochemistry on a film of these droplets we quantify changes in the electron transfer Gibbs energy, enthalpy, and entropy within the dense phase. Which we attribute to water’s highly structured hydrogen-bonding network within the droplets and, subsequently, around the redox probe. Further, we reveal via spatially resolved in situ Raman measurements that the change in reaction enthalpy is due to the destabilization of the product, ferrocyanide, within the ionic coacervate phase. The second part of my talk focuses on determining changes in electron transfer kinetics within these dense films relative to the bulk. Utilizing techniques such as Koutecký-Levich analysis and Butler-Volmer kinetics to quantify the electron transfer rate constant inside and outside of the coacervate. Together understanding redox thermodynamics and kinetics we hope to lend insight into whether coacervates could act as biological catalysts for primordial life.
