St. Elmo Brady Postdoctoral Inclusive Excellence Symposium

Dr. Ivan Moreno-Hernandez received a Bachelor of Science degree with University Honors in Chemistry and Physics from the University of Nebraska-Lincoln. Afterwards, Ivan continued his studies in Chemistry as an NSF Graduate Research Fellow with Prof. Nathan Lewis at the California Institute of Technology. Ivan focused on the study of semiconductor/metal-oxide heterojunctions for photoelectrochemical applications and on the discovery of earth-abundant electrocatalysts for anodic reactions in acidic electrolytes. Since 2019, Ivan has been a postdoctoral fellow with Prof. A. Paul Alivisatos at the University of California, Berkeley and has worked on understanding and controlling the reactive chemical environment created during liquid cell electron microscopy experiments.

Symposium title: Addressing renewable energy challenges through electrocatalyst discovery and in-situ nanoscale observations

Abstract: Electrochemical technologies can couple renewable energy sources with our chemical infrastructure, thereby enabling sustainable energy practices. The implementation of these technologies will rely on both the discovery of new electrochemical materials with improved performance and the development of techniques to understand complex reaction dynamics at the nanoscale. We will first discuss the discovery of an earth-abundant class of electrocatalysts, crystalline transition metal antimonates, that are thermodynamically stable for anodic reactions in acidic electrolytes. Our discussion will then focus on the development of redox-mediated liquid cell electron microscopy, a technique that allows electrochemical reactions to be observed in real time at near-atomic resolution.

Dr. Melanie R. McReynolds is a HHMI Hanna H. Gray postdoctoral fellow and Burroughs Wellcome Fund PDEP awardee at Princeton University, where her research focuses on the intersection of metabolic decline and aging. Melanie holds a B.S. degree in Chemistry and Physics from Alcorn State University. She participated in the NIH funded Alcorn State to Penn State Bridges to the Doctorate Program where she obtained her M.S. degree in Biological Sciences. Dr. McReynolds completed her Ph.D. in Biochemistry, Microbiology and Molecular Biology at the Pennsylvania State University. Melanie was recognized as a Rising Star on the CellPress list of Top 100 Inspiring Black Scientists in America and aims to inspire the next generation of scientists to trust that all things will work together for those who believe. Melanie is on the trajectory to establish her independent research group, where her future lab will shed light on metabolic aging and disease. She will return to Penn State as Dorothy Foehr Huck and J. Lloyd Huck Early Career Chair in Biochemistry and Molecular Biology—effective January 2022.

Symposium Title: NAD⁺ flux is maintained in aged mice

Abstract: NAD⁺ is an essential coenzyme found in all living cells. NAD⁺ concentrations decline during aging, but whether this reflects impaired production or accelerated consumption remains unclear. Here we employed isotope tracing and mass spectrometry to probe NAD⁺ metabolism across tissues in aged mice. In 25-month-old mice, we observe modest tissue NAD⁺ depletion (median decrease ~30%) without significant changes in circulating NAD⁺ precursors. Isotope tracing showed unimpaired synthesis of circulating nicotinamide from tryptophan, and maintained flux of circulating nicotinamide into tissue NAD⁺ pools. Although absolute NAD⁺ biosynthetic flux was maintained in most tissues of aged mice, fractional tissue NAD⁺ labeling from infused labeled nicotinamide was modestly accelerated, consistent with increased activity of NAD⁺ consuming enzymes. Thus, age-related decline in NAD⁺ is relatively subtle and driven by increased NAD⁺ consumer activity rather than impaired production.