Reactive oxygen species (ROS) are conventionally classified as toxic consequences of aerobic life. Although oxidative stress is implicated in a variety of diseases, mammals have evolved mechanisms to utilize at least one ROS, hydrogen peroxide (H2O2), for beneficial purposes. A comprehensive understanding of the balance between the pathology and physiology of H2O2 has remained elusive, due in large part to a dearth of tools that report specifically on this ROS. We developed a new class of small molecule tools for tracking H2O2 in living specimens. These probes were used to illuminate biological roles of this important ROS, including uncovering the first role for endogenous H2O2 signaling in healthy brain function.
In separate work, we sought to address two fundamental questions about evolutionary biology at the protein level: (i) If identical enzyme populations are subjected to distinct selection pressures before converging at a common evolutionary goal, will they evolve a common set of amino acid changes? (ii) How reproducible are the evolved similarities or differences? We combined phage-assisted continuous evolution (PACE) with high-throughput sequencing to analyze evolving protein populations over hundreds of rounds of evolution under varied conditions. This model system reveals, in molecular detail, how protein adaptation to different environments can influence future evolutionary outcomes, driven by interactions between mutations.