2024/05/23 by James P. Pidgeon, George A. Sutherland, Pidgeon, James P. +21
Biochemistry, Genetics and Molecular Biology · Medicine · Neuroscience · #Antioxidant Activity and Oxidative Stress #Chemical Physics (physics.chem-ph) #FOS: Physical sciences #Metabolomics and Mass Spectrometry Studies #Photoreceptor and optogenetics research
paper · pdf · doi:10.48550/arxiv.2405.14579
openalex publication_date 2024/05/23 · openalex created_date 2024/05/25 · openalex updated_date 2026/07/28
The orange carotenoid protein (OCP) is the water-soluble mediator of non-photochemical quenching in cyanobacteria, a crucial photoprotective mechanism in response to excess illumination. OCP converts from a dark-adapted inactive state (OCPo) to an active quenching conformation (OCPr) under high-light conditions, resulting in a concomitant redshift in the absorption of the bound carotenoid. Here, we test whether a long-lived carotenoid singlet excited state (S*) is required for this photoconversion. We measured pump wavelength-dependent transient absorption of OCPo trapped in trehalose-sucrose glass films. We found that initial OCP photoproducts are still formed despite the glass preventing completion to OCPr, and that S* is only apparent for <495 nm pumps. By comparison to the pump wavelength-dependence of the OCPo to OCPr conversion in buffer, we show that S* is not required for photoconversion, and that S* likely arises from ground-state heterogeneity within OCPo.