A blue light receptor that mediates RNA binding and translational regulation

Sensory photoreceptor proteins underpin light-dependent adaptations in nature and enable the optogenetic control of organismal behavior and physiology. We identified the bacterial light-oxygen-voltage (LOV) photoreceptor PAL that sequence-specifically binds short RNA stem loops with around 20 nM affinity in blue light and weaker than 1 µM in darkness. A crystal structure rationalizes the unusual receptor architecture of PAL with C-terminal LOV photosensor and N-terminal effector units. The light-activated PAL–RNA interaction can be harnessed to regulate gene expression at the RNA level as a function of light in both bacteria and mammalian cells. The present results elucidate a new signal-transduction paradigm in LOV receptors and conjoin RNA biology with optogenetic regulation, thereby paving the way toward hitherto inaccessible optoribogenetic modalities

Intraligand Charge Transfer Enables Visible‐Light‐Mediated Nickel‐Catalyzed Cross‐Coupling Reactions

We demonstrate that several visible‐light‐mediated carbon−heteroatom cross‐coupling reactions can be carried out using a photoactive NiII precatalyst that forms in situ from a nickel salt and a bipyridine ligand decorated with two carbazole groups (Ni(Czbpy)Cl2). The activation of this precatalyst towards cross‐coupling reactions follows a hitherto undisclosed mechanism that is different from previously reported light‐responsive nickel complexes that undergo metal‐to‐ligand charge transfer. Theoretical and spectroscopic investigations revealed that irradiation of Ni(Czbpy)Cl2 with visible light causes an initial intraligand charge transfer event that triggers productive catalysis. Ligand polymerization affords a porous, recyclable organic polymer for heterogeneous nickel catalysis of cross‐coupling reactions. The heterogeneous catalyst shows stable performance in a packed‐bed flow reactor during a week of continuous operation

Photocatalyst-free, visible-light-mediated nickel catalyzed carbon–heteroatom cross-couplings

Metallaphotocatalysis typically requires a photocatalyst to harness the energy of visible-light and transfer it to a transition metal catalyst to trigger chemical reactions. The most prominent example is the merger of photo- and nickel catalysis that unlocked various cross-couplings. However, the high reactivity of excited photocatalyst can lead to unwanted side reactions thus limiting this approach. Here we show that a bipyridine ligand that is subtly decorated with two carbazole groups forms a nickel complex that absorbs visible-light and promotes several carbon–heteroatom cross-couplings in the absence of an exogenous photocatalysts. The ligand can be polymerized in a simple one-step procedure to afford a porous organic polymer that can be used for heterogeneous nickel catalysis in the same reactions. The material can be easily recovered and reused multiple times maintaining high catalytic activity and selectivity