When lithium-oxygen batteries discharge, O2 is reduced at the cathode to form solid Li2O2. Understanding the fundamental mechanism of O2 reduction in aprotic solvents is therefore essential to realizing their technological potential. Two different models have been proposed for Li2O2 formation, involving either solution or electrode surface routes. Here, we describe a single unified mechanism, which, unlike previous models, can explain O2 reduction across the whole range of solvents and for which the two previous models are limiting cases. We observe that the solvent influences O2 reduction through its effect on the solubility of LiO2, or, more precisely, the free energy of the reaction LiO2(*) ⇌ Li(sol)(+) + O2(-)(sol) + ion pairs + higher aggregates (clusters). The unified mechanism shows that low-donor-number solvents are likely to lead to premature cell death, and that the future direction of research for lithium-oxygen batteries should focus on the search for new, stable, high-donor-number electrolytes, because they can support higher capacities and can better sustain discharge.

Electrochemical energy storage is one of the main societal challenges to humankind in this century. The performances of classical Li-ion batteries (LIBs) with non-aqueous liquid electrolytes have made great advances in the past two decades, but the intrinsic instability of liquid electrolytes results in safety issues, and the energy density of the state-of-the-art LIBs cannot satisfy the practical requirement. Therefore, rechargeable lithium metal batteries (LMBs) have been intensively investigated considering the high theoretical capacity of lithium metal and its low negative potential. However, the progress in the field of non-aqueous liquid electrolytes for LMBs has been sluggish, with several seemingly insurmountable barriers, including dendritic Li growth and rapid capacity fading. Solid polymer electrolytes (SPEs) offer a perfect solution to these safety concerns and to the enhancement of energy density. Traditional SPEs are dual-ion conductors, in which both cations and anions are mobile and will cause a concentration polarization thus leading to poor performances of both LIBs and LMBs. Single lithium-ion (Li-ion) conducting solid polymer electrolytes (SLIC-SPEs), which have anions covalently bonded to the polymer, inorganic backbone, or immobilized by anion acceptors, are generally accepted to have advantages over conventional dual-ion conducting SPEs for application in LMBs. A high Li-ion transference number (LTN), the absence of the detrimental effect of anion polarization, and the low rate of Li dendrite growth are examples of benefits of SLIC-SPEs. To date, many types of SLIC-SPEs have been reported, including those based on organic polymers, organic-inorganic hybrid polymers and anion acceptors. In this review, a brief overview of synthetic strategies on how to realize SLIC-SPEs is given. The fundamental physical and electrochemical properties of SLIC-SPEs prepared by different methods are discussed in detail. In particular, special attention is paid to the SLIC-SPEs with high ionic conductivity and high LTN. Finally, perspectives on the main challenges and focus on the future research are also presented.

Eight proteins, defects in which are associated with Meckel-Gruber syndrome and nephronophthisis ciliopathies, work together as two functional modules at the transition zone to establish basal body/transition zone connections with the membrane and barricade entry of non-ciliary components into this organelle.

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Control of silk fibroin concentration in aqueous solutions via osmotic stress was studied to assess relationships to gel formation and structural, morphological, and functional (mechanical) changes associated with this process. Environmental factors potentially important in the in vivo processing of aqueous silk fibroin were also studied to determine their contributions to this process. Gelation of silk fibroin aqueous solutions was affected by temperature, Ca(2+), pH, and poly(ethylene oxide) (PEO). Gelation time decreased with increase in protein concentration, decrease in pH, increase in temperature, addition of Ca(2+), and addition of PEO. No change of gelation time was observed with the addition of K(+). Upon gelation, a random coil structure of the silk fibroin was transformed into a beta-sheet structure. Hydrogels with fibroin concentrations >4 wt % exhibited network and spongelike structures on the basis of scanning electron microscopy. Pore sizes of the freeze-dried hydrogels were smaller as the silk fibroin concentration or gelation temperature was increased. Freeze-dried hydrogels formed in the presence of Ca(2+) exhibited larger pores as the concentration of this ion was increased. Mechanical compressive strength and modulus of the hydrogels increased with increase in protein concentration and gelation temperature. The results of these studies provide insight into the sol-gel transitions that silk fibroin undergoes in glands during aqueous processing while also providing important insight in the in vitro processing of these proteins into useful new materials.

Targeted genome editing technologies are powerful tools for studying biology and disease, and have a broad range of research applications. In contrast to the rapid development of toolkits to manipulate individual genes, large-scale screening methods based on the complete loss of gene expression are only now beginning to be developed. Here we report the development of a focused CRISPR/Cas-based (clustered regularly interspaced short palindromic repeats/CRISPR-associated) lentiviral library in human cells and a method of gene identification based on functional screening and high-throughput sequencing analysis. Using knockout library screens, we successfully identified the host genes essential for the intoxication of cells by anthrax and diphtheria toxins, which were confirmed by functional validation. The broad application of this powerful genetic screening strategy will not only facilitate the rapid identification of genes important for bacterial toxicity but will also enable the discovery of genes that participate in other biological processes.

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Lithium metal (Li ) rechargeable batteries (LMBs), such as systems with a Li anode and intercalation and/or conversion type cathode, lithium-sulfur (Li-S), and lithium-oxygen (O )/air (Li-O /air) batteries, are becoming increasingly important for electrifying the modern transportation system, with the aim of sustainable mobility. Although some rechargeable LMBs (e.g. Li /LiFePO batteries from Bolloré Bluecar, Li-S batteries from OXIS Energy and Sion Power) are already commercially viable in niche applications, their large-scale deployment is hampered by a number of formidable challenges, including growth of lithium dendrites, electrolyte instability towards high voltage intercalation-type cathodes, the poor electronic and ionic conductivities of sulfur (S ) and O , as well as their corresponding reduction products (e.g. Li S and Li O), dissolution, and shuttling of polysulfide (PS) intermediates. This leads to a short lifecycle, low coulombic/energy efficiency, poor safety, and a high self-discharge rate. The use of electrolyte additives is considered one of the most economical and effective approaches for circumventing these problems. This Review gives an overview of the various functional additives that are being applied and aims to stimulate new avenues for the practical realization of these appealing devices.