Summer Wu
Pronouns: she/her
Research Mentor(s): James Penner-Hahn
Research Mentor School/College/Department: Chemistry and Biophysics / LSA
Program:
Authors: Summer Wu, Alivia Mukherjee, David Cooper, Roseanne Sension, Nicolai Lehnert, James Penner-Hahn
Session: Session 3: 11:00 am – 11: 50 am
Poster: 38
Abstract
Vitamin B12, also known as cobalamin, has recently gained significant attention due to its pivotal role as a light-sensitive cofactor in certain non-photosynthetic bacteria. In these organisms, adenosylcobalamin (AdoCbl) is found in the transcription regulator protein called CarH, where its photosensitivity regulates the production of protective carotenoid pigments. Upon photolysis, light cleaves the chemical bond between the central cobalt atom and the adenosyl group. The dissociated adenosyl radical quenches itself by forming a double bond, making an alkene product. It was previously reported that the presence of a weak base is necessary for the formation of this alkene product from various cobalamin derivatives in organic solvents (West et al., 2020). In our experiments, we synthesized two novel alkylcobalamins, phenylhexylcobalamin (PhHxCbl) and naphthylethylcobalamin (NapEtCbl), as model complexes to investigate the reaction conditions, kinetics, and mechanism behind AdoCbl’s unique role in CarH. Time-resolved and steady-state UV-Vis absorption spectroscopy was performed to characterize the change in cobalt oxidation state caused by photolysis. GC-MS was then performed to identify the organic product after photolysis. Interestingly, we have determined that the alkene product is formed in both basic and neutral conditions. These results further develop our understanding of the kinetics and mechanism behind how CarH regulates carotenoid biosynthesis and raise promise for a controllable, potentially biocompatible method for alkene synthesis.
