Local morphological and dimensional changes of enzyme-degraded cellulose materials measured by atomic force microscopy

A study of the degradation effects of enzyme treatment on the dimensional changes of cellulose aggregate fibrils (CAFs) with dimensions of ∼100,000 × 3,000 × 300 nm from fully bleached kraft fiber was performed. CAFs were incubated with cellulase for up to 32 h. The insoluble CAFs fragments remaining after enzymatic hydrolysis were then subjected to variable relative humidity (RH). Each sample was imaged by an atomic force microscope (AFM) in tapping mode. The images were analyzed to determine the dimensional changes of the insoluble CAFs. Enzymatic hydrolysis continuously depolymerized the CAFs over 32 h, ultimately causing 20% of the CAFs to become soluble. Compared to initial dimensions of the reference CAFs with no enzymatic treatment, the dimensions of the enzyme treated CAFs were generally more responsive to humidity and exhibited an increased frequency of plastic deformations.     

Review of Acetic Acid Synthesis from Various Feedstocks Through Different Catalytic Processes

Acetic acid (AA) has been largely used with a wide range of applications such as a raw material for a synthesis of vinyl acetate monomer, cellulose acetate or acetate anhydrate, acetate ester and a solvent for a synthesis of terephthalic acid and so on. The present paper briefly summarizes the commercialized chemical processes with their Rh or Ir-based catalytic systems in a liquid-phase carbonylation reaction such as Monsanto, Cativa and Acetica processes. In addition, some alternative catalytic systems such as heterogeneous catalysts to produce AA by direct oxidation or indirect carbonylation of dimethyl ether through BP-SaaBre process in a gas-phase reaction to solve some problems such as a difficult separation of homogeneous catalysts in a corrosive reaction medium. Some home-made heterogeneous catalysts such as a rhodium incorporated graphitic carbon nitride (Rh-g-C₃N₄) and some heterogenized homogeneous catalysts using the supports of tungsten carbide, iron oxide or graphitic carbon nitride containing rhodium complexes were also introduced for the synthesis of AA through a liquid-phase methanol carbonylation reaction to effectively solve the leaching problem of active rhodium metal as well as to mitigate the separation problem of homogeneous catalysts.     

Unusually Stable Triazine‐based Organic Superstructures

Solid‐state reactions have been rapidly gaining popularity in organic chemistry owing to their simplicity, efficiency, and selectivity compared to liquid‐phase reactions. Herein, we describe the formation of superstructures through the solid‐state reaction of an organic single‐crystal. The superstructure of 5,5′,5′′‐(1,3,5‐triazine‐2,4,6‐triyl)triisophthalonitrile (TIPN) can be formed by cyclotrimerization of 1,3,5‐tricyanobenzene (TCB) single crystals. The TIPN superstructure was confirmed by single crystal X‐ray diffraction and visualized by transmission electron microscopy. The superstructure has hexagonally packed 1‐dimensional (1D) channels along the crystal axis. Furthermore, the superstructure arises from interdigitated nitrile interactions in the crystal lattice, and thus has electron‐beam tolerance and very high thermal stability.     

An anion receptor with NH and OH groups for hydrogen bonds

An anion receptor with NH and OH groups as hydrogen bond donors has been prepared, and both groups are simultaneously involved in hydrogen bonding with anions.     

A designed metal-organic framework based on a metal-organic polyhedron

A C(3) symmetric ligand with three 1,3-benzenedicarboxylate units has been used to construct a metal-organic framework with a (3,24)-connected network topology, where the nanometre-sized metal-organic cuboctahedra (MOCs) have been incorporated solely into a cubic close packing (CCP) arrangement, which led to superoctahedral and supertetrahedral cavities.     

Photodissociation of Hydrated Hydrogen Iodide Clusters

Using high‐level ab initio calculations and excited state ab initio molecular dynamics simulations, we show that hydrated iodic acids release hydrogen radicals and/or hydrogen molecules as well as iodine radicals upon excitation. Its photoreaction process involving charge transfer to the solvent takes place in four steps: 1) hydration of the acid, 2) charge transfer to water upon excitation of hydrated acid, 3) detachment of the neutral iodine atom, and 4) detachment of the hydrogen radical. The iodine detachment process from excited hydrated hydro–iodic acids is exothermic and the detachment of hydrogen radicals from hydrated hydronium radicals is spontaneous if the initial kinetic energy of the cluster is high enough to get over the activation barrier of the detachment. The complete release of the radicals can be understood in terms of kinetics. This study shows how the hydrogen and halogen radicals are dissociated and released from their hydrated acids. Simple experiments corroborate our predicted mechanism for the release of hydrogen molecules from iodic acid in water by ultraviolet light.     

Comparison of photophysical properties of the hemicyanine dyes in ionic and nonionic solvents

The fluorescence properties of 4-[4-(dimethylamino)styryl]-1-n-alkylpyridinium bromide (hemicyanine) dissolved in solvents of different polarities and viscosities (methanol, ethylene glycol, tetra-ethylene glycol, glycerol, benzyl alcohol, pyridine, and two ionic liquids, 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIM]BF4, and 1-butyl-3-methylimidazolium hexafluorophosphate, [BMIM]PF6) were investigated. Significant increase in the fluorescence quantum yield and the fluorescence decay lifetime was observed with the increase in the viscosity of the solvent medium. It is because the intramolecular rotational motion of the molecule becomes more difficult in viscous liquid, which leads to a decrease in the nonradiative decay processes. The fluorescence quantum yields for all of the solutions followed a semiempirical law that depends only on the solvent viscosity. The correlation function C(t) was obtained for each solution by joining fluorescence decay curves measured at different wavelengths. From the fitted results of C(t), we observed the distinctive feature unique to the ionic liquids, in which the correlation functions for ionic liquid solutions are fitted to be biphasic, while they are monophasic for other solvents. The fluorescence maximum of hemicyanine dissolved in these ionic liquids red-shifted following the increase in the excitation wavelength.     

Synthesis and characterization of a bis-μ,η-carboxylate-bridged dinuclear manganese(II) complex containing a tetradentate tripodal ligand, N-(benzimidazol-2-ylmethyl)iminodiacetic acid

The dinuclear Mn(II) complex, [Mn₂(Hbida)₂(H₂O)₂], was prepared using a tetradentate tripodal ligand, N-(benzimidazol-2-ylmethyl)iminodiacetic acid (H₃bida) which has two carboxylate and one benzimidazole groups. The manganese ions are doubly bridged using μ,η¹-bridging monodentate carboxylate oxygen atoms. The Mn–Mn bond distance of 3.446 Å in the complex is comparable to that observed in the active site of the native manganese arginase enzyme (3.30 Å). The geometry of the complex with four carboxylates in two different types of binding modes, non-bridging monodentate and μ,η¹-type bridging monodentate, mimics the active site structure of manganese arginase. The magnetic properties of the complex show a coupling constant of J = −0.471(1) cm⁻¹, which is consistent with weakly coupled antiferromagnetic Mn^II (S = 5/2) centers. The cyclic voltammograms of the Mn(II) complex in DMF show irreversible oxidation occurring around 570 mV (versus Ag/AgCl).     

The 'hybrid cell': a new compensated infinity cell for larger radius ion excitation in Fourier transform ion cyclotron resonance mass spectrometry

A new 'hybrid' ion cyclotron resonance (ICR) trap is proposed and analyzed by computer simulations. The trap is basically a hybrid of a segmented end cap (Infinity) and capacitively coupled cylindrical cell, with additional electrodes placed at the center of each end cap. The new trap produces an on-axis electric field z-profile similar to that of the Infinity cell or capacitively coupled open cylindrical cell during ion excitation. Simion simulations demonstrate that, during detection, appropriate changes of the potentials applied to the two new sets of electrodes produce a radial electric field z-profile that more closely approaches that for an ideal axial three-dimensional quadrupolar potential at high post-excitation ICR orbital radius, for improved signal-to-noise ratio and resolving power, and minimal m/z-discrimination.