ParaHydrogen Polarized Ethyl-[1-13C]pyruvate in Water,a Key Substrate for Fostering the PHIP-SAH Approach to Metabolic Imaging

An efficient synthesis of vinyl-[1-¹³C]pyruvate has been reported, from which ¹³C hyperpolarized (HP) ethyl-[1-¹³C]pyruvate has been obtained by means of ParaHydrogen Induced Polarization (PHIP). Due to the intrinsic lability of pyruvate, which leads quickly to degradation of the reaction mixture even under mild reaction conditions, the vinyl-ester has been synthesized through the intermediacy of a more stable ketal derivative. ¹³C and ¹H hyperpolarizations of ethyl-[1-¹³C]pyruvate, hydrogenated using ParaHydrogen, have been compared to those observed on the more widely used allyl-derivative. It has been demonstrated that the spin order transfer from ParaHydrogen protons to ¹³C, is more efficient on the ethyl than on the allyl-esterdue to the larger J-couplings involved. The main requirements needed for the biological application of this HP product have been met, i. e. an aqueous solution of the product at high concentration (40 mM) with a good ¹³C polarization level (4.8 %) has been obtained. The in vitro metabolic transformation of the HP ethyl-[1-¹³C]pyruvate, catalyzed by an esterase, has been observed. This substrate appears to be a good candidate for in vivo metabolic investigations using PHIP hyperpolarized probes.     

Elucidating the Influence of Electrical Potentials on the Formation of Charged Oligopeptide Self-Assembled Monolayers on Gold

Self-assembled monolayers (SAMs) based on oligopeptides have garnered immense interest for a wide variety of innovative biomedical and electronic applications. However, to exploit their full potential, it is necessary to understand and control the surface chemistry of oligopeptides. Herein, we report on how different electrical potentials affect the adsorption kinetics, stability and surface coverage of charged oligopeptide SAMs on gold surfaces. Kinetic analysis using electrochemical surface plasmon resonance (e-SPR) reveals a slower oligopeptide adsorption rate at more positive or negative electrical potentials. Additional analysis of the potential-assisted formed SAMs by X-ray photoelectron spectroscopy demonstrates that an applied electrical potential has minimal effect on the packing density. These findings not only reveal that charged oligopeptides exhibit a distinct potential-assisted assembly behaviour but that an electrical potential offers another degree of freedom in controlling their adsorption rate.     

Feasible Tuning of Surface OVs on (001) TiO2 for Superior Photocatalytic Nitrogen Fixation Activity

A feasible tuning method for oxygen vacancies was realized by annealing under 3 atm H₂ with (001)-exposed TiO₂ nanosheets. The colored TiO₂ sample exhibits an excellent N₂ photo-fixation rate owing to the abundant oxygen vacancies (OVs) thus demonstrating that annealing with high pressure H₂ is exceedingly efficient for tuning surface OVs.     

CRISPR-Cas12a System for Biosensing and Gene Regulation

Clustered regularly interspaced short palindromic repeats (CRISPR) is a promising technology in the biological world. As one of the CRISPR-associated (Cas) proteins, Cas12a is an RNA-guided nuclease in the type V CRISPR-Cas system, which has been a robust tool for gene editing. In addition, due to the discovery of target-binding-induced indiscriminate single-stranded DNase activity of Cas12a, CRISPR-Cas12a also exhibits great promise in biosensing. This minireview not only gives a brief introduction to the mechanism of CRISPR-Cas12a but also highlights the recent developments and applications in biosensing and gene regulation. Finally, future prospects of the CRISPR-Cas12a system are also discussed. We expect this minireview will inspire innovative work on the CRISPR-Cas12a system by making full use of its features and advantages.     

Chiral Interlocked Corrole Dimers Directly Linked at Inner Carbon Atoms of Confused Pyrrole Rings

A facile synthetic strategy towards conformationally stable chiral chromophores based on dimeric porphyrinoids has been established. A peculiar class of face-to-face intramolecularly interlocked corrole dimers were formed by the oxidative C−C coupling linked at the inner carbon sites upon simple treatment of copper(II) ions. Their intrinsic electronic structures were modulated by the peripheral corrole ring annulations, which lead to distinct optical properties and redox profiles. The stereogenic carbon centers implemented in the confused corrole skeleton provided a rationale for designing novel chiral materials.     

Recent Advances of Freestanding Cathodes for Li-S Batteries

Lithium-sulfur batteries (LSBs) with high energy density and low cost have been recognized as one of the most promising next-generation energy storage systems. Although it has taken decades of development, the practical application of LSBs has been hindered by several inherent obstacles, particularly the severe shuttle effect and sluggish reaction kinetics in the sulfur cathode. Various strategies have been proposed to address these problems via rational design of electrode materials and configurations. Freestanding sulfur cathode could be a promising strategy to improve the sulfur mass loading at the cathode level and energy density of LSBs. This minireview will briefly summary the recent advances in freestanding cathodes for LSBs. The advantages and disadvantages of various freestanding cathodes are discussed and the prospects for the development of flexible cathodes are envisioned.     

Natural Cellulose Substance Based Energy Materials

Natural cellulose substances have been proven to be ideal structural templates and scaffolds for the fabrication of artificial functional materials with designed structures, psychochemical properties and functionalities. They possess unique hierarchically porous network structures with flexible, biocompatible, and environmental characteristics, exhibiting great potentials in the preparation of energy-related materials. This minireview summarizes natural cellulose-based materials that are used in batteries, supercapacitors, photocatalytic hydrogen generation, photoelectrochemical cells, and solar cells. When natural cellulose substances are employed as the structural template or carbon sources of energy materials, the three-dimensional porous interwoven structures are perfectly replicated, leading to the enhanced performances of the resultant materials. Benefiting from the mechanical strengths of natural cellulose substances, wearable, portable, free-standing, and flexible materials for energy storage and conversion are easily obtained by using natural cellulose substances as the substrates.     

Heavier Tetrylenes as Single Site Catalysts

An overview of the development of compounds with heavier low-valent group 14 elements (known as tetrylenes) as single component catalyst for organic transformation has been provided. Compounds with heavier group 14 elements possess stereochemically active lone pairs and energetically accessible π-antibonding orbitals, thereby resembling the electronic configuration of transition-metal compounds. Such compounds with low-valent group 14 elements has been known for small molecule activation since Power's report of dihydrogen activation by a digermyne, but their utilization in catalysis remained as a “Holy Grail” in main group chemistry. In recent years, numerous methodologies have been discovered epitomizing the use of Si(II), Ge(II) and Sn(II) compounds as single site catalysts for hydroboration of aldehydes, ketones, pyridines, cyanosilylation of aldehydes and ketones, N-formylations aromatic amines, dehydrocoupling reactions. This mini-review highlights these significant developments with an emphasis on the mechanistic investigation.     

pH-Sensitive Oscillatory Motion of a Urease Motor on the Urea Aqueous Phase

A self-propelled object coupled with an enzyme reaction between urease and urea was investigated at the air/aqueous interface. A plastic object that was fixed to a urease-immobilized filter paper was used as a self-propelled object, termed a urease motor, placed on an aqueous urea solution. The driving force of the urease motor is the difference in the surface tension around the object. Oscillatory motion or no motion was triggered depending on the initial pH of the urea solution. Both the frequency and maximum speed of the oscillatory motion varied depending on the initial pH of the water phase. The mechanisms underlying the oscillatory motion and no motion were discussed in relation to the bell-shaped enzyme activity of urease in the enzyme reaction and the surface tension around the urease motor.     

Nickel-Catalyzed Cross-Coupling of Ethyl Chlorofluoroacetate with Aryl Bromides

A combinatorial nickel-catalyzed monofluoroalkylation of aryl bromides with the industrial raw regent ethyl chlorofluoroacetate has been developed. The two key factors to successful conversion are the combination of nickel with readily available nitrogen and phosphine ligands and the using of a mixture of different solvents. Mechanistic investigations indicated a new zinc regent might generated in situ and be involved in the reaction process.