Enzymatic metabolons dramatically enhance metabolic fluxes of low-efficiency biochemical reactions.

In this work, we investigate how spatial proximity of enzymes belonging to the same pathway (metabolon) affects metabolic flux. Using off-lattice Langevin dynamics simulations in tandem with a stochastic reaction-diffusion protocol and a semi-analytical reaction-diffusion model, we systematically explored how strength of protein-protein interactions, catalytic efficiency, and protein-ligand interactions affect metabolic flux through the metabolon. Formation of a metabolon leads to a greater speedup for longer pathways and especially for reaction-limited enzymes, whereas, for fully optimized diffusion-limited enzymes, the effect is negligible. Notably, specific cluster architectures are not a prerequisite for enhancing reaction flux. Simulations uncover the crucial role of optimal nonspecific protein-ligand interactions in enhancing catalytic efficiency of a metabolon. Our theory implies, and bioinformatics analysis confirms, that longer catalytic pathways are enriched in less optimal enzymes, whereas most diffusion-limited enzymes populate shorter pathways. Our findings point toward a plausible evolutionary strategy where enzymes compensate for less-than-optimal efficiency by increasing their local concentration in the clustered state.

Different states and the associated fates of biomolecular condensates.

Biomolecular condensates are functional assemblies, which can enrich intrinsically disordered proteins (IDPs) and/or RNAs at concentrations that are orders of magnitude higher than the bulk. In their native functional state, these structures can exist in multiple physical states including liquid-droplet phase, hydrogels, and solid assemblies. On the other hand, an aberrant transition between these physical states can result in loss-of-function or a gain-of-toxic-function. A prime example of such an aberrant transition is droplet aging-a phenomenon where some condensates may progressively transition into less dynamic material states at biologically relevant timescales. In this essay, we review structural and viscoelastic roots of aberrant liquid-solid transitions. Also, we highlight the different checkpoints and experimentally tunable handles, both active (ATP-dependent enzymes, post-translational modifications) and passive (colocalization of RNA molecules), that could alter the material state of assemblies.

Tether-free photothermal deep-brain stimulation in freely behaving mice via wide-field illumination in the near-infrared-II window.

Neural circuitry is typically modulated via invasive brain implants and tethered optical fibres in restrained animals. Here we show that wide-field illumination in the second near-infrared spectral window (NIR-II) enables implant-and-tether-free deep-brain stimulation in freely behaving mice with stereotactically injected macromolecular photothermal transducers activating neurons ectopically expressing the temperature-sensitive transient receptor potential cation channel subfamily V member 1 (TRPV1). The macromolecular transducers, ~40 nm in size and consisting of a semiconducting polymer core and an amphiphilic polymer shell, have a photothermal conversion efficiency of 71% at 1,064 nm, the wavelength at which light attenuation by brain tissue is minimized (within the 400-1,800 nm spectral window). TRPV1-expressing neurons in the hippocampus, motor cortex and ventral tegmental area of mice can be activated with minimal thermal damage on wide-field NIR-II illumination from a light source placed at distances higher than 50 cm above the animal's head and at an incident power density of 10 mW mm-2. Deep-brain stimulation via wide-field NIR-II illumination may open up opportunities for social behavioural studies in small animals.

Designing Copper-Based Catalysts for Efficient Carbon Dioxide Electroreduction.

The electroreduction of carbon dioxide (CO2 ) has been emerging as a high- potential approach for CO2 utilization using renewables. When copper (Cu) based catalysts are used, this platform can produce multi-carbon (C2+ ) fuels and chemicals with almost net-zero emission, contributing to the closure of the anthropogenic carbon cycle. Nonetheless, the rational design and development of Cu-based catalysts are critical toward the realization of highly selective and efficient CO2 electroreduction. In this review, first the latest advances in Cu-catalyzed CO2 electroreduction in the product selectivity and electrocatalytic activity are briefly summarized. Then, recent theoretical and mechanistic studies of CO2 electroreduction on Cu-based catalysts are investigated, which serve as programs to design catalysts. Strategies for devising Cu catalysts that aim at promoting different key elementary steps for hydrocarbon and C2+ oxygenates production are further summarized. Moreover, challenges in understanding the mechanism, operando investigation of Cu catalysts and reactions, and systems' influences are also presented. Finally, the future prospects of CO2 electroreduction are discussed.

Fast cooling induced grain-boundary-rich copper oxide for electrocatalytic carbon dioxide reduction to ethanol.

Electrochemical CO2 reduction with rationally designed copper-based electrocatalysts is a promising approach to reduce CO2 emission and produce value-added products. Grain boundaries and micron-strains inside catalysts have been proposed as active catalytic sites, while the controlled formation of these sites has remained highly challenging. In this work, we developed a strategy of creating high-density grain boundaries and micron-strains inside CuO electrocatalysts by fast cooling with liquid nitrogen. Compared to samples with slower cooling rates, the fast cooled CuO showed clear difference in their crystal domain sizes, micro-strain densities, and the chemisorption capacities of CO2 and CO. This micro-strain-rich CuO electrocatalyst exhibited a high total current density over 300 mA·cm-2, and an outstanding Faradaic efficiency for C2 products (with a majority to ethanol) at -1.0 V vs. reversible hydrogen electrode. Our work suggests a facile approach of tuning grain boundaries and micro-strains inside Cu-based electrocatalysts to scale up electrochemical CO2 reduction for high value-added products.

Sono-optogenetics facilitated by a circulation-delivered rechargeable light source for minimally invasive optogenetics.

Optogenetics, which uses visible light to control the cells genetically modified with light-gated ion channels, is a powerful tool for precise deconstruction of neural circuitry with neuron-subtype specificity. However, due to limited tissue penetration of visible light, invasive craniotomy and intracranial implantation of tethered optical fibers are usually required for in vivo optogenetic modulation. Here we report mechanoluminescent nanoparticles that can act as local light sources in the brain when triggered by brain-penetrant focused ultrasound (FUS) through intact scalp and skull. Mechanoluminescent nanoparticles can be delivered into the blood circulation via i.v. injection, recharged by 400-nm photoexcitation light in superficial blood vessels during circulation, and turned on by FUS to emit 470-nm light repetitively in the intact brain for optogenetic stimulation. Unlike the conventional "outside-in" approaches of optogenetics with fiber implantation, our method provides an "inside-out" approach to deliver nanoscopic light emitters via the intrinsic circulatory system and switch them on and off at any time and location of interest in the brain without extravasation through a minimally invasive ultrasound interface.

Efficient solar-driven electrocatalytic CO2 reduction in a redox-medium-assisted system.

Solar-driven electrochemical carbon dioxide (CO2) reduction is capable of producing value-added chemicals and represents a potential route to alleviate carbon footprint in the global environment. However, the ever-changing sunlight illumination presents a substantial impediment of maintaining high electrocatalytic efficiency and stability for practical applications. Inspired by green plant photosynthesis with separate light reaction and (dark) carbon fixation steps, herein, we developed a redox-medium-assisted system that proceeds water oxidation with a nickel-iron hydroxide electrode under light illumination and stores the reduction energy using a zinc/zincate redox, which can be controllably released to spontaneously reduce CO2 into carbon monoxide (CO) with a gold nanocatalyst in dark condition. This redox-medium-assisted system enables a record-high solar-to-CO photoconversion efficiency of 15.6% under 1-sun intensity, and an outstanding electric energy efficiency of 63%. Furthermore, it allows a unique tuning capability of the solar-to-CO efficiency and selectivity by the current density applied during the carbon fixation.

Tuning of CO2 Reduction Selectivity on Metal Electrocatalysts.

Climate change, caused by heavy CO2 emissions, is driving new demands to alleviate the rising concentration of atmospheric CO2 levels. Enlightened by the photosynthesis of green plants, photo(electro)chemical catalysis of CO2 reduction, also known as artificial photosynthesis, is emerged as a promising candidate to address these demands and is widely investigated during the past decade. Among various artificial photosynthetic systems, solar-driven electrochemical CO2 reduction is widely recognized to possess high efficiencies and potentials for practical application. The efficient and selective electroreduction of CO2 is the key to the overall solar-to-chemical efficiency of artificial photosynthesis. Recent studies show that various metallic materials possess the capability to play as electrocatalysts for CO2 reduction. In order to achieve high selectivity for CO2 reduction products, various efforts are made including studies on electrolytes, crystal facets, oxide-derived catalysts, electronic and geometric structures, nanostructures, and mesoscale phenomena. In this Review, these methods for tuning the selectivity of CO2 electrochemical reduction of metallic catalysts are summarized. The challenges and perspectives in this field are also discussed.