We describe an engineered fluorescent optogenetic sensor, SuperClomeleon, that robustly detects inhibitory synaptic activity in single, cultured mouse neurons by reporting intracellular chloride changes produced by exogenous GABA or inhibitory synaptic activity. Using a cell-free protein engineering automation methodology that bypasses gene cloning, we iteratively constructed, produced, and assayed hundreds of mutations in binding-site residues to identify improvements in Clomeleon, a first-generation, suboptimal sensor. Structural analysis revealed that these improvements involve halide contacts and distant side chain rearrangements. The development of optogenetic sensors that respond to neural activity enables cellular tracking of neural activity using optical, rather than electrophysiological, signals. Construction of such sensors using in vitro protein engineering establishes a powerful approach for developing new probes for brain imaging.

Luminopsins are fusion proteins of luciferase and opsin that allow interrogation of neuronal circuits at different temporal and spatial resolutions by choosing either extrinsic physical or intrinsic biological light for its activation. Building on previous development of fusions of wild-type Gaussia luciferase with channelrhodopsin, here we expanded the utility of luminopsins by fusing bright Gaussia luciferase variants with either channelrhodopsin to excite neurons (luminescent opsin, LMO) or a proton pump to inhibit neurons (inhibitory LMO, iLMO). These improved LMOs could reliably activate or silence neurons in vitro and in vivo. Expression of the improved LMO in hippocampal circuits not only enabled mapping of synaptic activation of CA1 neurons with fine spatiotemporal resolution but also could drive rhythmic circuit excitation over a large spatiotemporal scale. Furthermore, virus-mediated expression of either LMO or iLMO in the substantia nigra in vivo produced not only the expected bidirectional control of single unit activity but also opposing effects on circling behavior in response to systemic injection of a luciferase substrate. Thus, although preserving the ability to be activated by external light sources, LMOs expand the use of optogenetics by making the same opsins accessible to noninvasive, chemogenetic control, thereby allowing the same probe to manipulate neuronal activity over a range of spatial and temporal scales.luciferase | bioluminescence | neural circuitry | substantia nigra | hippocampus

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Numerous efforts in improving the hydrogen evolution reaction (HER) performance of transition metal dichalcogenides mostly focus on active sites exposing, vacancy engineering, and phase engineering. However, little room is left for improvement in these approaches. It should be noted that efficient electron transfer also plays a crucial role in catalytic activity. In this work, by employment of an external vertical magnetic field, ferromagnetic bowl-like MoS 2 flakes can afford electrons transmitting easily from a glassy carbon electrode to active sites to drive HER, and thus perform magnetic HER enhancement. The ferromagnetic bowl-like MoS 2 flakes with an external vertical magnetic field can provide a roughly doubled current density compared to that without an external vertical magnetic field at a constant overpotential of −150 mV. Our work may provide a new pathway to break the bottleneck for further improvement of HER performance and also paves the way to utilize the magnetic enhancement in widely catalytic application.