High-resolution electron microscopy of microstructure of MnF2 subjected to shock compression at 4.4 GPa

Microstructure of MnF₂ subjected to by shock compression at 4.4 GPa was examined using transmission electron microscopy (TEM). Lamellar structure consisting of twin-related domains of rutile-structure and intergrowth of α- PbO₂-type phase is observed in the electron diffraction pattern and TEM images. The crystallographic relationship between rutile and α- PbO₂-type phases can be expressed as and .     

The Sixth Painlevé Equation as Similarity Reduction of $${\widehat{\mathfrak{gl}}_3}$$ Generalized Drinfel’d–Sokolov Hierarchy

Scaling symmetry of -type Drinfel’d–Sokolov hierarchy is investigated. Applying similarity reduction to the hierarchy, one can obtain the Schlesinger equation with (n + 1) regular singularities. Especially in the case of n = 3, the hierarchy contains the three-wave resonant system and the similarity reduction gives the generic case of the Painlevé VI equation. We also discuss Weyl group symmetry of the hierarchy.      

Facile Synthesis of Dibenzopentalene Dianions and Their Application as New π‐Extended Ligands

Reduction of phenyl(silyl)ethynes with potassium followed by quenching with iodine gave dibenzopentalenes in moderate yields. The intermediates of the reactions, dipotassium dibenzopentalenides, were isolated. The first dibenzopentalene–transition‐metal complex was successfully synthesized. The ruthenium atoms are located above the six‐membered rings. However, X‐ray diffraction analysis and theoretical calculations revealed that the aromatic nature of the five‐membered rings was retained. The cyclic voltammetry of the Ru complex revealed two oxidation waves with relatively large separation.     

Selective Generation of Formamides through Photocatalytic CO2 Reduction Catalyzed by Ruthenium Carbonyl Compounds

The selective formation of dialkyl formamides through photochemical CO₂ reduction was developed as a means of utilizing CO₂ as a C₁ building block. Photochemical CO₂ reduction catalyzed by a [Ru(bpy)₂(CO)₂]²⁺ (bpy: 2,2′‐bipyridyl)/[Ru(bpy)₃]²⁺/Me₂NH/Me₂NH₂⁺ system in CH₃CN selectively produced dimethylformamide. In this process a ruthenium carbamoyl complex ([Ru(bpy)₂(CO)(CONMe₂)]⁺) formed by the nucleophilic attack of Me₂NH on [Ru(bpy)₂(CO)₂]²⁺ worked as the precursor to DMF. Thus Me₂NH acted as both the sacrificial electron donor and the substrate, while Me₂NH₂⁺ functioned as the proton source. Similar photochemical CO₂ reductions using R₂NH and R₂NH₂⁺ (R=Et, nPr, or nBu) also afforded the corresponding dialkyl formamides (R₂NCHO) together with HCOOH as a by‐product. The main product from the CO₂ reduction transitioned from R₂NCHO to HCOOH with increases in the alkyl chain length of the R₂NH. The selectivity between R₂NCHO and HCOOH was found to depend on the rate of [Ru(bpy)₂(CO)(CONR₂)]⁺ formation.     

Exploiting the Potential of Meroterpenoid Cyclases to Expand the Chemical Space of Fungal Meroterpenoids

Fungal meroterpenoids are a diverse group of hybrid natural products with impressive structural complexity and high potential as drug candidates. In this work, we evaluate the promiscuity of the early structure diversity-generating step in fungal meroterpenoid biosynthetic pathways: the multibond-forming polyene cyclizations catalyzed by the yet poorly understood family of fungal meroterpenoid cyclases. In total, 12 unnatural meroterpenoids were accessed chemoenzymatically using synthetic substrates. Their complex structures were determined by 2D NMR studies as well as crystalline-sponge-based X-ray diffraction analyses. The results obtained revealed a high degree of enzyme promiscuity and experimental results which together with quantum chemical calculations provided a deeper insight into the catalytic activity of this new family of non-canonical, terpene cyclases. The knowledge obtained paves the way to design and engineer artificial pathways towards second generation meroterpenoids with valuable bioactivities based on combinatorial biosynthetic strategies.     

A new method for estimating the relative binding free energy,derived from a free energy variational principle for the Pim-1-kinase–ligand and FKBP–ligand systems

Journal of Computer-Aided Molecular Design - In this study, a new method is proposed for calculating the relative binding free energy between a ligand and a protein, derived from a free energy...     

An “OFF–ON–OFF” fluorescence protein-labeling probe for real-time visualization of the degradation of short-lived proteins in cellular systems

The ability to monitor proteolytic pathways that remove unwanted and damaged proteins from cells is essential for understanding the multiple processes used to maintain cellular homeostasis. In this study, we have developed a new protein-labeling probe that employs an ‘OFF–ON–OFF’ fluorescence switch to enable real-time imaging of the expression (fluorescence ON) and degradation (fluorescence OFF) of PYP-tagged protein constructs in living cells. Fluorescence switching is modulated by intramolecular contact quenching interactions in the unbound probe (fluorescence OFF) being disrupted upon binding to the PYP-tag protein, which turns fluorescence ON. Quenching is then restored when the PYP-tag–probe complex undergoes proteolytic degradation, which results in fluorescence being turned OFF. Optimization of probe structures and PYP-tag mutants has enabled this fast reacting ‘OFF–ON–OFF’ probe to be used to fluorescently image the expression and degradation of short-lived proteins.

An “OFF–ON–OFF” fluorescence probe for real-time imaging of the expression (fluorescence ‘OFF’) and degradation (fluorescence ‘ON’) of short lived PYP-tag proteins in cellular systems.     

An Ultrastable,Small {Ag7}5+ Nanocluster within a Triangular Hollow Polyoxometalate Framework

Small Ag_n nanoclusters (n<10) have been emerging as promising materials as sensing, biolabeling, and catalysis because of their unique electronic states and optical properties. However, studying synthesis, structure determination, and exploration of their properties remain major challenges as a result of the low stability of small Ag nanoclusters. Herein, we synthesized an atomically precise face‐centered‐cubic‐type small {Ag₇}⁵⁺ nanocluster supported by a novel triangular hollow polyoxometalate (POM) framework [Si₃W₂₇O₉₆]^18?. The cluster showed unique {Ag₇}⁵⁺‐to‐POM charge transfer bands in both visible and UV light regions. Furthermore, this small {Ag₇}⁵⁺ nanocluster exhibited an unprecedented ultrastability in solution, despite having exposed Ag sites that can be accessed by small molecules, such as O₂, water, and solvents.