Bio-based and Biodegradable Electrospun Fibers Composed of Poly(L-lactide) and Polyamide 4

Novel bio-based and biodegradable block copolymers were synthesized by "click" reaction between poly(L-lactide)(PLLA) and polyamide 4(PA4). Upon tuning the molar mass of PLLA block, the properties of copolymers and electrospun ultrafine fibers were investigated and compared with those of PLLA and PA4 blends. PLLA and PA4 were found incompatible and formed individual crystalline regions, along with reciprocal inhibition in crystallization. Electrospun fibers were highly hydrophobic, even if hydrophilic PA4 was the rich component. The crystallinity of either PLLA or PA4 decreased after electrospinning and PLLA-rich as-spun fibers were almost amorphous. Immersion tests proved that fibers of block copolymers were relatively homogeneous with micro-phase separation between PLLA and PA4. The fibrous structures of copolymers were different from those of the fibers electrospun from blends, for which sheath-core structure induced by macro-phase separation between homopolymers of PLLA and PA4 was confirmed by TEM, EDS, and XPS.     

Hydrophobic Shielding of Outer Surface: Enhancing the Chemical Stability of Metal–Organic Polyhedra

Metal–organic polyhedra (MOP) are a promising class of crystalline porous materials with multifarious potential applications. Although MOPs and metal–organic frameworks (MOFs) have similar potential in terms of their intrinsic porosities and physicochemical properties, the exploitation of carboxylate MOPs is still rudimentary because of the lack of systematic development addressing their chemical stability. Herein we describe the fabrication of chemically robust carboxylate MOPs via outer‐surface functionalization as an a priori methodology, to stabilize those MOPs system where metal–ligand bond is not so strong. Fine‐tuning of hydrophobic shielding is key to attaining chemical inertness with retention of the framework integrity over a wide range of pH values, in strong acidic conditions, and in oxidizing and reducing media. These results are further corroborated by molecular modelling studies. Owing to the unprecedented transition from instability to a chemically ultra‐stable regime using a rapid ambient‐temperature gram‐scale synthesis (within seconds), a prototype strategy towards chemically stable MOPs is reported.     

Boron‐Containing Probes for Non‐optical High‐Resolution Imaging of Biological Samples

Boron has been employed in materials science as a marker for imaging specific structures by electron energy loss spectroscopy (EELS) or secondary ion mass spectrometry (SIMS). It has a strong potential in biological analyses as well; however, the specific coupling of a sufficient number of boron atoms to a biological structure has proven challenging. Herein, we synthesize tags containing closo‐1,2‐dicarbadodecaborane, coupled to soluble peptides, which were integrated in specific proteins by click chemistry in mammalian cells and were also coupled to nanobodies for use in immunocytochemistry experiments. The tags were fully functional in biological samples, as demonstrated by nanoSIMS imaging of cell cultures. The boron signal revealed the protein of interest, while other SIMS channels were used for imaging different positive ions, such as the cellular metal ions. This allows, for the first time, the simultaneous imaging of such ions with a protein of interest and will enable new biological applications in the SIMS field.     

Interfacing Formate Dehydrogenase with Metal Oxides for the Reversible Electrocatalysis and Solar‐Driven Reduction of Carbon Dioxide

The integration of enzymes with synthetic materials allows efficient electrocatalysis and production of solar fuels. Here, we couple formate dehydrogenase ( FDH ) from Desulfovibrio vulgaris Hildenborough (DvH) to metal oxides for catalytic CO₂ reduction and report an in‐depth study of the resulting enzyme–material interface. Protein film voltammetry (PFV) demonstrates the stable binding of FDH on metal‐oxide electrodes and reveals the reversible and selective reduction of CO₂ to formate. Quartz crystal microbalance (QCM) and attenuated total reflection infrared (ATR‐IR) spectroscopy confirm a high binding affinity for FDH to the TiO₂ surface. Adsorption of FDH on dye‐sensitized TiO₂ allows for visible‐light‐driven CO₂ reduction to formate in the absence of a soluble redox mediator with a turnover frequency (TOF) of 11±1 s^?1. The strong coupling of the enzyme to the semiconductor gives rise to a new benchmark in the selective photoreduction of aqueous CO₂ to formate.     

Acyl‐Phosphide Anions via an Intermediate with Carbene Character: Reactions of K[PtBu2] and CO

The analogy of the reactivity of group 1 phosphides to that of FLPs is further demonstrated by reactions with CO, affording a new synthetic route to acyl‐phosphide anions. The reaction of [K(18‐crown‐6)][PtBu₂] ( 1 ) with CO affords [(18‐crown‐6)K?THF₂][Z‐tBuP=C(tBu)O] ( 2?THF₂ ) as the major product, and the minor product [K₆(18‐crown‐6)][(tBu₂PCO)₂]₃ ( 3 ). Species 2 reacts with either BPh₃ or additional CO to give [K(18‐crown‐6)][(Ph₃B)tBuPC(tBu)O] ( 4 ) and [K(18‐crown‐6)][(OCtBu)₂P] ( 5 ), respectively. The acyl‐phosphide anion 2 is thought to be formed by a photochemically induced radical process involving a transient species with triplet carbene character, prompting 1,2‐tert‐butyl group migration. A similar process is proposed for the subsequent reaction of 2 with CO to give 5 .     

Concise Synthesis of Potassium Acyltrifluoroborates from Aldehydes through Copper(I)‐Catalyzed Borylation/Oxidation

Potassium acyltrifluoroborates (KATs) were prepared through copper(I)‐catalyzed borylation of aldehydes and subsequent oxidation. This synthetic route is characterized by the wide range of aldehydes accessible, favorable step economy, mild reaction conditions, and tolerance of various functional groups, and it enables the facile generation of a range of KATs, for example, bearing halide, sulfide, acetal, or ester moieties. Moreover, this method was applied to the three‐step synthesis of various α‐amino acid analogues that bear a KAT moiety on the C‐terminus by using naturally occurring amino acids as the starting material.     

Channel‐Rich RuCu Nanosheets for pH‐Universal Overall Water Splitting Electrocatalysis

Channel‐rich RuCu snowflake‐like nanosheets (NSs) composed of crystallized Ru and amorphous Cu were used as efficient electrocatalysts for oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and overall water splitting in pH‐universal electrolytes. The optimized RuCu NSs/C‐350 °C and RuCu NSs/C‐250 °C show attractive activities of OER and HER with low overpotentials and small Tafel slopes, respectively. When applied to overall water splitting, the optimized RuCu NSs/C can reach 10 mA cm^?2 at cell voltages of only 1.49, 1.55, 1.49 and 1.50 V in 1 m KOH, 0.1 m KOH, 0.5 m H₂SO₄ and 0.05 m H₂SO₄, respectively, much lower than those of commercial Ir/C∥Pt/C. The optimized electrolyzer exhibits superior durability with small potential change after up to 45 h in 1 m KOH, showing a class of efficient functional electrocatalysts for overall water splitting.     

Characterization of a Citrulline 4‐Hydroxylase from Nonribosomal Peptide GE81112 Biosynthesis and Engineering of Its Substrate Specificity for the Chemoenzymatic Synthesis of Enduracididine

The GE81112 tetrapeptides are a small family of unusual nonribosomal peptide congeners with potent inhibitory activity against prokaryotic translation initiation. With the exception of the 3‐hydroxy‐l ‐pipecolic acid unit, little is known about the biosynthetic origins of the non‐proteinogenic amino acid monomers of the natural product family. Here, we elucidate the biogenesis of the 4‐hydroxy‐l ‐citrulline unit and establish the role of an iron‐ and α‐ketoglutarate‐dependent enzyme (Fe/αKG) in the pathway. Homology modelling and sequence alignment analysis further facilitate the rational engineering of this enzyme to become a specific 4‐arginine hydroxylase. We subsequently demonstrate the utility of this engineered enzyme in the synthesis of a dipeptide fragment of the antibiotic enduracidin. This work highlights the value of applying a bioinformatics‐guided approach in the discovery of novel enzymes and engineering of new catalytic activity into existing ones.