Browsing by Subject "Photochemistry"

Now showing 1 - 2 of 2
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    B12-based photoreceptors: from structure and function to applications in optogenetics and synthetic biology
    (2019-08) Pérez-Castaño, Ricardo; Elías Arnanz, Montserrat; Padmanabhan Iyer, Subramanian; Genética y Microbiología
    Vitamin B12-based photoreceptor proteins sense ultraviolet (UV), blue or green light using 5´-deoxyadenosylcobalamin (AdoCbl). The prototype of this widespread bacterial photoreceptor family, CarH, controls light-dependent gene expression in photoprotective cellular responses. It represses transcription in the dark by binding to operator DNA as an AdoCbl-bound tetramer, whose disruption by light relieves operator binding to allow transcription. Structures of the "dark" (free and DNA-bound) and "light" CarH states and studies on the unusual AdoCbl photochemistry have provided fundamental insights into these photoreceptors. We highlight these, the plasticity within a conserved mode of action among CarH homologs, their distribution, and their promising applications in optogenetics and synthetic biology.
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    Catalysis in the excited state: bringing innate transition metal photochemistry into play
    (American Chemical Society, 2005-03-05) Juliá Hernández, Fabio; Química Inorgánica; Facultad de Química
    Transition metal catalysis is an indispensable tool for organic synthesis that has been harnessed, modulated and perfected for many decades by careful selection of metal centers and ligands, giving rise to synthetic methods with unparalleled efficiency and chemoselectivity. Recent developments have demonstrated how light irradiation can also be recruited as a powerful tool to dramatically alter the outcome of catalytic reactions, providing access to innovative pathways with remarkable synthetic potential. In this context, the adoption of photochemical conditions as a mainstream strategy to drive organic reactions has unveiled exciting opportunities to exploit the rich excited-state framework of transition metals for catalytic applications. This Perspective examines the advances on the application of transition metal complexes as standalone photocatalysts, exploiting the innate reactivity of their excited states beyond the common use as photoredox catalysts. An account of relevant examples is dissected to provide a discussion on the electronic reorganization, the orbitals involved and the associated reactivity of different types of excited states. This analysis aims to provide practitioners with fundamental principles and guiding strategies to understand, design and apply light-activation strategies to homogeneous transition metal catalysis for organic synthesis.