Dynamic analysis of aggregation of methylene blue with polarized optical waveguide spectroscopy

Polarized optical waveguide (POW) spectroscopy permits analysis of the changing molecular state of methylene blue (MB), including aggregate order and orientation at the waveguide surface. Monomer or dimer, dissolved randomly in MB aqueous solution, tends to aggregate at the waveguide surface during air drying. Furthermore, POW spectroscopy dynamically revealed that MB molecules became oriented vertically to the waveguide surface with increasing aggregation order.     

A Cell‐Targeted Non‐Cytotoxic Fluorescent Nanogel Thermometer Created with an Imidazolium‐Containing Cationic Radical Initiator

A cationic fluorescent nanogel thermometer based on thermo‐responsive N‐isopropylacrylamide and environment‐sensitive benzothiadiazole was developed with a new azo compound bearing imidazolium rings as the first cationic radical initiator. This cationic fluorescent nanogel thermometer showed an excellent ability to enter live mammalian cells in a short incubation period (10 min), a high sensitivity to temperature variations in live cells (temperature resolution of 0.02–0.84 °C in the range 20–40 °C), and remarkable non‐cytotoxicity, which permitted ordinary cell proliferation and even differentiation of primary cultured cells.     

Structure Determination of an AgI‐Mediated Cytosine–Cytosine Base Pair within DNA Duplex in Solution with 1H/15N/109Ag NMR Spectroscopy

The structure of an Ag^I‐mediated cytosine–cytosine base pair, C–Ag^I–C, was determined with NMR spectroscopy in solution. The observation of 1‐bond ¹⁵N‐¹⁰⁹Ag J‐coupling (¹J(¹⁵N,¹⁰⁹Ag): 83 and 84 Hz) recorded within the C–Ag^I–C base pair evidenced the N3–Ag^I–N3 linkage in C–Ag^I–C. The triplet resonances of the N4 atoms in C–Ag^I–C demonstrated that each exocyclic N4 atom exists as an amino group (?NH₂), and any isomerization and/or N4–Ag^I bonding can be excluded. The 3D structure of Ag^I–DNA complex determined with NOEs was classified as a B‐form conformation with a notable propeller twist of C–Ag^I–C (?18.3±3.0°). The ¹⁰⁹Ag NMR chemical shift of C‐Ag^I‐C was recorded for cytidine/Ag^I complex (δ(¹⁰⁹Ag): 442 ppm) to completed full NMR characterization of the metal linkage. The structural interpretation of NMR data with quantum mechanical calculations corroborated the structure of the C–Ag^I–C base pair.     

Copolymerization of Ethylene and Polar Monomers by Using Ni/IzQO Catalysts

The replacement of precious metals in catalysis by earth‐abundant metals is currently one of the urgent challenges for chemists. Whereas palladium‐catalyzed copolymerization of ethylene and polar monomers is a valuable method for the straightforward synthesis of functionalized polyolefins, the corresponding nickel‐based catalysts have suffered from poor thermal tolerance and low molecular weight of the polymers formed. Herein, we report a series of neutral nickel complexes bearing imidazo[1,5‐a]quinolin‐9‐olate‐1‐ylidene (IzQO) ligands. The Ni/IzQO system can catalyze ethylene polymerization at 50–100 °C with reasonable activity in the absence of any cocatalyst, whereas most known nickel‐based catalysts are deactivated at this temperature range. The Ni/IzQO catalyst was successfully applied to the copolymerization of ethylene with allyl monomers to obtain the corresponding copolymers with the highest molecular weight reported for a Ni‐catalyzed system.     

Phenol Derivatives Obtained from Grape Seed Extract Show Virucidal Activity against Murine Norovirus

Human noroviruses are the most common pathogens known to cause acute gastroenteritis, a condition that can lead to severe illness among immunocompromised individuals such as organ transplant recipients and the elderly. To date, no safe and effective vaccines or therapeutic agents have been approved for treating norovirus infections. Therefore, we aimed to demonstrate the virucidal activity of grape seed extract (GSE), which contains >83% proanthocyanidins, against murine norovirus (MNV), a surrogate for human norovirus. GSE showed virucidal activity against MNV in a dose- and time-dependent manner. Atomic force microscopic analysis showed viral particle aggregates after treatment of MNV with GSE. MNV treated with 50 µg/mL of GSE for 10 min resulted in the absence of pathogenicity in an animal model of infection, indicating that GSE has irreversible virucidal activity against MNV particles. Thus, GSE may aid in the development of treatments for norovirus infections.     

The Spermine–Bisaryl Conjugate as a Potent Inducer of B‐ to Z‐DNA Transition

DNA containing alternating purine and pyrimidine repeats has the potential to adopt the Z‐DNA structure, one of the well‐studied structures besides A‐ and B‐DNA. Despite a number of molecular models that have been proposed to explain the mechanism for B→Z transition, there is continued discussion on the mechanism and physiological role of this transition. In this study, we have found that the bis(2‐naphthyl)‐maleimide–spermine conjugate ( 3 c ) exhibits a remarkable ability to cause the B→Z transition of d(CGCGCG)₂ at low salt concentrations. Using isothermal titration calorimetry (ITC) we show that the B→Z transition induced by 3 c is both enthalpically and entropically favorable. The ligand might effect the dehydration of B‐DNA, which leads to the B→Z transition. Interestingly, an intermediate CD between the B and Z forms was observed in the pH‐dependent transition in the presence of the ligand. The unique structure and characteristics of the ligand designed in this investigation will be useful for the study of Z‐DNA.     

Synthesis of anionic methylpalladium complexes with phosphine-sulfonate ligands and their activities for olefin polymerization

Reaction of diarylphosphinobenzene-2-sulfonic acids with tertially amines, followed by addition of [PdMeCl(cod)], provided anionic methylpalladium(II) complexes with bidentate phosphine-sulfonate ligands, which show high activity for copolymerization of ethylene with methyl acrylate.     

Hydrated Ionic Liquids: Perspective for Bioscience

Hydrated ionic liquid (IL) is a simple mixture of IL and water. Unique aqueous electrolyte solution can be designed by mixing IL with limited amount of water. In most hydrated ILs, there are no free water and all are strongly interacted with ions. The properties of hydrated ILs, such as polarity, viscosity, ion mobility, and hydrogen bonding ability, can therefore be controlled simply by water content. This mixture is expected to provide similar environment to that of living cell, and is desired to be effective solvents for biomolecules. In this account, we would like to survey the basic properties, recent results, and future aspects of the hydrated ILs.