Publications

Trifluoromethylation via broken C-F bonds Trifluoromethyl substituents are widely used in pharmaceutical research to tune the properties of drug candidates. Generally, they are introduced intact through the formation of carbon-carbon bonds. Levin et al. discovered an unusual alternative mechanism, in which borane abstracts fluoride from the CF 3 group in a gold complex. The activated CF 2 fragment can then bond to a wide variety of other carbon substituents added to the same gold center. Return of the fluoride liberates a trifluoromethylated compound from the metal. This mechanism could be useful for the introduction of radioactive fluoride substituents for positron emission tomography applications. Science , this issue p. 1272

Route instability is an important contributor to data plane unreliability on the Internet and also incurs load on the control plane of routers. In this paper, we study how route selection schemes can avoid these changes in routes. Modifying route selection implies a tradeoff between stability, deviation from operators' preferred routes, and availability of routes. We develop algorithms to lower-bound the feasible points in these tradeoff spaces. We also propose a new approach, Stable Route Selection (SRS), which uses flexibility in route selection to improve stability without sacrificing availability and with a controlled amount of deviation. Through large-scale simulation, a software-router implementation, and an emulation with real-world BGP update feeds, we demonstrate that SRS is a promising approach to safely stabilize route selection.

Domesticated microalgae hold great promise for the sustainable provision of various bioresources for human domestic and industrial consumption. Efforts to exploit their potential are far from being fully realized due to limitations in the know-how of microalgal engineering. The associated technologies are not as well developed as those for heterotrophic microbes, cyanobacteria and plants. However, recent studies on microalgal metabolic engineering, genome editing and synthetic biology have helped immensely to enhance transformation efficiencies and are bringing new insights into this field. Therefore, this article summarizes recent developments in microalgal biotechnology and examines the prospect of generating specialty and commodity products through the processes of metabolic engineering and synthetic biology. After a brief examination of empirical engineering methods and vector design, the article focuses on quantitative transformation cassette design, elaborates on target-editing methods and emerging digital design of algal cellular metabolism to arrive at high yields of valuable products. These advances have enabled a transition of manners in microalgal engineering from single-gene and enzyme-based metabolic engineering to systems-level precision engineering, from cells created with genetically modified (GM) tags to those without GM tags, and ultimately from proof of concept to tangible industrial application. Finally, future trends are proposed in microalgal engineering, aiming to establish individualized transformation systems in newly identified species for strain-specific specialty and commodity products, while developing sophisticated universal toolkits in model algal species.

We integrated text-mined synthesis data with chemical reaction network analysis to reveal nitrite-bridging dimerization driving BiFeO 3 phase formation.

Here, we present a fabrication procedure that can produce large-area, size-tunable, periodic silicon nanopillar arrays, using metal templates that are created via nanosphere lithography. The size of the silicon nanopillars can be systematically controlled by an oxidation and etching process. The smallest size of nanopillars fabricated via this method is ∼9 nm, and the area covered with nanopillars is >1 cm2. Using this approach and nanoimprint lithography, it is possible to pattern sub-10-nm metal nanoparticles with a particle density as high as 1 × 109 particles/cm2.

Catalyst platforms that promote multielectron charge delocalization offer an attractive approach to achieving the CO2 reduction reaction (CO2RR) with selectivity over the competing hydrogen evolution reaction (HER). Here, we show the importance of metal-ligand exchange coupling as an example of charge delocalization that can determine efficiency for photocatalytic CO2RR. A comparative evaluation of iron and cobalt complexes supported by the redox-active ligand tpyPY2Me establishes that the two-electron reduction of [Co(tpyPY2Me)]2+ ([Co]2+) occurs at potentials 770 mV more negative than the [Fe(tpyPY2Me)]2+ ([Fe]2+) analog by maximizing exchange coupling in the latter compound. The positive shift in reduction potential promoted by metal-ligand exchange coupling drives [Fe]2+ to be among the most active and selective molecular catalysts for photochemical CO2RR reported to date, maintaining up to 99% CO product selectivity with total turnover numbers (TON) and initial turnover frequencies (TOF) exceeding 30,000 and 900 min–1, respectively. In contrast, [Co]2+ shows much lower CO2RR activity, reaching only ca. 600 TON at 83% CO product selectivity under similar conditions accompanied by rapid catalyst decomposition. Spin density plots of the two-electron reduced [Co]0 complex implicate a paramagnetic open-shell doublet ground state compared to the diamagnetic open-shell singlet ground state of reduced [Fe]0, rationalizing the observed negative shift in two-electron reduction potentials from the [M]2+ species and lowered CO2RR efficiency for the cobalt complex relative to its iron congener. This work emphasizes the contributions of multielectron metal-ligand exchange coupling in promoting effective CO2RR and provides a starting point for the broader incorporation of this strategy in catalyst design.