Spatiotemporal fluorescence mapping of redox activity in lipid membranes

AYA SAKAYA; ANDRES M. DURANTINI; TARA SVERKO; VINCENT WIECZNY; GONZALO COSA

Conferencia; 102nd Canadian Chemistry Conference and Exhibition; 2019

Lipid membranes have gained wide attention as assembly scaffolds, owingto their ability to self-assemble into well-defined fluid structures, allowingthe compartmentalization and direct assembly of components of interest in afluid platform. Model lipid membranes offer the opportunity to mimic and studyprocesses occurring across these fluid mosaics such as respiration, transportand signaling. Armed with a spectroelectrochemistry microscopy setup, inthis study we have explored redox reactions within lipid membranes, proof ofconcept experiments intended to address the response of membrane embedded redoxsystems. Experimentally, a supported lipid bilayer was formed on top on anindium tin oxide (ITO)-coated glass. H4ClPrB-PMHC, a redox sensitivefluorogenic probe bearing the chromanol moiety of α-tocopherol (Vitamin E), anda BODIPY tail segment was incorporated within the lipid membrane. The electrochemicaland optical properties were next studied using our total internal reflectionfluorescence (TIRF) microscopy based spectro-electrochemical (SEC) setup, thatenables monitoring emission while minimizing background by virtue of sampling asmall ~ 300 nm region above the glass water interface, while also controllingthe redox potential at the basal leaflet of the lipid membrane. Our results are consistent with oxidation of thechromanol moiety of the probe into a chromanone moiety through an irreversibleprocess that elicits fluorescence, and further thermally induced rearrangementof the newly formed chromanone into a chromoquinone. We will discuss thegeneral methodology, results, and implications of the work in the context ofelectron transport through relay redox systems.