Photometric and Chemical Kinetic Studies of Singlet Oxygen Quenching by Native and Acid-Blue β-Carotene: Implications for the 515nm Effect in Photosynthesis
Claire Elise Hendrickson, Ashlee Wertz
β–carotene (βC) is an orange pigment present in green plants, where it plays a protective role against the harmful effects of light. It does this by deactivating “singlet oxygen”— a toxic oxidizing species generated during photosynthesis. During photosynthesis, βC temporarily converts from its “native orange βC” state to a “pink βC” state. We hypothesized that pink βC will quench singlet oxygen less efficiently than native orange βC. To test this hypothesis, we chemically modeled pink βC with “blue βC–TCA complexes”, created by reacting βC with trichloroacetic acid (TCA). The singlet oxygen quenching efficiency of native βC and βC–TCA complexes was characterized in two ways. First, in the summer of 2017, we measured the rate of degradation of the singlet oxygen substrate DPBF in the presence of native βC and βC–TCA complexes. Second, in the summer of 2018, we used a near–infrared photometric detector to measure the intensity I1270 near–infrared 1,270 nm light emitted by singlet oxygen in the presence of native orange βC and blue βC–TCA complexes. Surprisingly, our DPBF–based and I1270–based results all indicate that native orange βC and blue βC–TCA complexes quench singlet oxygen with roughly equal efficiency. In the summer of 2019, I will use the Chemistry Department’s computational Gaussian software to characterize the sensitivity of the triplet state of βC (3βC) to the presence of electrically polarized environments such as those present in βC–TCA complexes and in pink βC. Because 3βC likely plays a crucial role in the deactivation of singlet oxygen, and because βC–TCA complexes are structurally similar to pink βC, these studies will provide new insights into the role of pink βC in photosynthesis.
Mark B. Masthay
Primary Advisor's Department
Stander Symposium project
"Photometric and Chemical Kinetic Studies of Singlet Oxygen Quenching by Native and Acid-Blue β-Carotene: Implications for the 515nm Effect in Photosynthesis" (2019). Stander Symposium Projects. 1713.