Measuring Protein Dynamics in Levitated Microdroplets

VIOLA FIELGEIN, Michael Jacobs, Texas State University

     Abstract Number: 454
     Working Group: Aerosol Chemistry

Abstract
It is increasingly appreciated that the unique physicochemical properties of microdroplets are capable of accelerating a wide array of different chemistries compared to reactions in macroscale solutions. While much has been made about the increasing importance of surface reactions in microdroplets, we still lack a fundamental understanding of the molecular mechanisms driving accelerated chemistry in microdroplets. Notably, several recent studies have observed significantly accelerated biochemical reactions in microdroplets, including post-translational modifications and protein digestion. It is well understood that proteins adsorb to the air-water interface and denature, but the extent and nature of this process in microdroplets and its impact on reaction kinetics such as enzymatic reactions, remain unclear.

To develop a more fundamental understanding of how confinement in microdroplets can lead to altered enzymatic kinetics, we are using single droplet levitation techniques to study the dynamics and reaction kinetics of proteins in individual microdroplets with well-defined compositions. Here, we describe our recent work examining the dynamics of a model protein, green fluorescent protein (GFP), in levitated microdroplets of different compositions. Microdroplets are levitated within a quadrupole electrodynamic trap (QET), and the folded state of GFP is assessed in situ by monitoring changes in fluorescence intensity over time. Our preliminary results show that GFP intensity can significantly decrease in microdroplets in second to minute timescales, suggesting the protein’s structure is perturbed in microdroplets. Because similar changes in fluorescence intensity are not observed in macroscale solutions with the same compositions, we believe that partitioning to the air-water interface is the main driving force altering protein dynamics in microdroplets. Ultimately, by studying protein dynamics in microdroplets of different size and composition, we aim to tease out whether the rate acceleration of biochemical reactions in microdroplets is a surface driven process or if there is some other driving force.