Professor Alex Sessions (Caltech) - "The hydrogen isotope fingerprints of life."


Wednesday, October 17, 2018, 4:00pm to 5:30pm


Haller Hall, Geological Museum, 24 Oxford Street




Most biologic processes exhibit significant deuterium isotope effects, which can measurably alter the abundances of stable hydrogen isotopes (1H and 2H) in biomolecules. A longstanding hope is that different organisms, reactions, or environments will result in characteristic 2H/1H ratios that we can learn to interpret. In this seminar I will summarize our efforts to understand the biochemical mechanisms that control H-isotopic fractionation in lipids, molecules that are well preserved in the sedimentary record and potentially offer insight into ancient metabolism and environments. In contrast to C and N isotopes, H-isotope signals arise from a combination of effects distributed across central metabolism, particularly those that conserve reducing power as NADPH. Both depletions and enrichments of 2H in the same environment are simultaneously possible, and provide a potential biosignature. We will conclude by considering the likelihood of such fingerprints being preserved in rocks from the early Earth, or in extraterrestrial materials.