O6‐Alkylguanine‐DNA Alkyltransferase‐Mediated Repair of O4‐Alkylated 2′‐Deoxyuridines

O⁶‐Alkylguanine‐DNA alkyltransferases (AGTs) are responsible for the removal of O⁶‐alkyl 2′‐deoxyguanosine (dG) and O⁴‐alkyl thymidine (dT) adducts from the genome. Unlike the E. coli OGT (O⁶‐alkylguanine‐DNA‐alkyltransferase) protein, which can repair a range of O⁴‐alkyl dT lesions, human AGT (hAGT) only removes methyl groups poorly. To uncover the influence of the C5 methyl group of dT on AGT repair, oligonucleotides containing O⁴‐alkyl 2′‐deoxyuridines (dU) were prepared. The ability of E. coli AGTs (Ada‐C and OGT), human AGT, and an OGT/hAGT chimera to remove O⁴‐methyl and larger adducts (4‐hydroxybutyl and 7‐hydroxyheptyl) from dU were examined and compared to those relating to the corresponding dT species. The absence of the C5 methyl group resulted in an increase in repair observed for the O⁴‐methyl adducts by hAGT and the chimera. The chimera was proficient at repairing larger adducts at the O⁴ atom of dU. There was no observed correlation between the binding affinities of the AGT homologues to adduct‐containing oligonucleotides and the amounts of repair measured.     

Large‐Scale Synthesis of Vertically Aligned ZnO Hexagonal Nanotube‐Rod Hybrids Using a Two‐Step Growth Method

Zn‐polar (0001) surfaces are more chemically reactive than other surfaces of ZnO crystals and drive preferential anisotropic and asymmetric growth along the [0001] direction, which facilitates growth of c‐axis oriented, one‐dimensional ZnO nanostructures. Accordingly, capping the top (0001) surface of ZnO crystals can impede c‐axis growth and thus serve to modulate growth habits. In this study, we generated vertically aligned ZnO hexagonal nanotube‐rod (h‐NTR) hybrids by modulating growth habits during a second‐stage process. Electron microscopy studies revealed the formation of very thin (10–20 nm) single‐crystalline nanotube walls along the edges of underlying hexagonal rod tops capped with Si. In addition, spatially resolved investigation of ZnO h‐NTR indicated an abrupt increase in the measured bandgap across rod‐tube junctions, which was ascribed to a quantum confinement effect and Burstein–Moss effect of carriers within the very thin nanotube walls.     

One‐Step Fast Synthesis of Li4Ti5O12 Particles Using an Atmospheric Pressure Plasma Jet

A one‐step process to fabricate crystalline Li₄Ti₅O₁₂(LTO) particles directly from solution using an atmospheric pressure plasma jet (APPJ) is reported. This process uses Ti and Li ions‐containing salt solutions as the precursor, which is ultrasonically nebulized and then transported to the downstream of the APPJ using a carrier gas. With an extremely short contact time (<0.1 s) between the precursor droplets and the plasma jet, crystalline LTO can be fabricated in one step without additional rinse and postannealing steps. The LTO particle size can be effectively controlled using a preheater, the precursor solution composition and concentration, and the carrier gas flow rate. By properly adjusting the operating condition, particles of diameters from 100 nm to few μm with various morphologies can be obtained. When used as an electrode material, the resulting LTO powders fabricated under selected conditions show specific capacities over 100 mAh/g even at 50 C rate.     

Multivalent Display and Receptor‐Mediated Endocytosis of Transferrin on Virus‐Like Particles

The structurally regular and stable self‐assembled capsids derived from viruses can be used as scaffolds for the display of multiple copies of cell‐ and tissue‐targeting molecules and therapeutic agents in a convenient and well‐defined manner. The human iron‐transfer protein transferrin, a high affinity ligand for receptors upregulated in a variety of cancers, has been arrayed on the exterior surface of the protein capsid of bacteriophage Qβ. Selective oxidation of the sialic acid residues on the glycan chains of transferrin was followed by introduction of a terminal alkyne functionality through an oxime linkage. Attachment of the protein to azide‐functionalized Qβ capsid particles in an orientation allowing access to the receptor binding site was accomplished by the Cu^I‐catalyzed azide–alkyne cycloaddition (CuAAC) click reaction. Transferrin conjugation to Qβ particles allowed specific recognition by transferrin receptors and cellular internalization through clathrin‐mediated endocytosis, as determined by fluorescence microscopy on cells expressing GFP‐labeled clathrin light chains. By testing Qβ particles bearing different numbers of transferrin molecules, it was demonstrated that cellular uptake was proportional to ligand density, but that internalization was inhibited by equivalent concentrations of free transferrin. These results suggest that cell targeting with transferrin can be improved by local concentration (avidity) effects.     

The Synthesis of Ba‐ and Fe‐ Substituted CsAlSi2O6 Pollucites

Barium‐substituted CsAlSi₂O₆ pollucites, Cs_xBa_(1?x)/2AlSi₂O₆, and barium‐ and iron‐substituted pollucites, Cs_xBa_(1?x)/2Al_xFe_1?xSi₂O₆ and Cs_xBa_1?xAl_xFe_1?xSi₂O₆ were synthesized with 1 ≥ x≥ 0.7 using a hydrothermal synthesis procedure. Rietveld analysis of X‐ray diffraction data confirmed the substitution of Ba for Cs and Fe for Al, respectively. The crystallographic analysis also describes the effects of three different types of pollucite substitutions on the pollucite unit cell: Ba²⁺ for Cs¹⁺ cation results in little effect on cell dimensions, intermediate concentrations of Ba²⁺ and Fe³⁺ substitution result in net minor expansion due to Fe³⁺ addition, and large Ba and Fe substitutions result in overall framework contraction. Elemental analysis combined with microscopy further supports the phase purity of these new phases. These materials can be used to study the stability of CsAlSi₂O₆ as a durable ceramic waste form, which could accommodate with time Cs and its decay product, Ba. Furthermore, success in iron substitution for aluminum into the pollucite lattice predicts that redox charge compensation for Cs cation decay is possible.     

Synthesis of Small‐Scale Boron‐Rich Nano‐Size Particles

The synthesis times required to produce high energy density compounds (C₂B₄H₂)_n and (C₂B₁₀H₄)_n by gas phase pyrolysis of the carboranes C₂B₄H₆ and C₂B₁₀H₁₂, respectively, have been measured at 1150–2000 K and carborane pressures of (0.3–3.0)⋅10⁻³ MPa. Kinetic model simulations of the synthesis have been performed. The temperatures, carborane pressures, and synthesis times required to produce small‐scale (C₂B₄H₂)_n and (C₂B₁₀H₄)_n particles of 10 to 30 nm diameter are determined.     

Enantioselective Synthesis of Azaflavanones Using Organocatalytic 6‐endo Aza‐Michael Addition

A method to prepare highly enantioenriched azaflavanones using an organocatalytic 6‐endo aza‐Michael addition has been described. A variety of 2‐aryl‐, 2‐vinyl‐ and 2‐methylazaflavanones were prepared in good yields (53–84%) and excellent enantioselectivities (97.6:2.4 to 99.3:0.7 er).

     

A Sucrose‐Mediated Sol–Gel Technique for the Synthesis of MgO–Y2O3 Nanocomposites

A sucrose‐mediated aqueous sol–gel procedure was developed to synthesize MgO–Y₂O₃ nanocomposite ceramics for potential optical applications. The synthesis involves the generation of a precursor foam containing Mg²⁺ and Y³⁺ cations via the chemical and thermal degradation of sucrose molecules in aqueous solution. Subsequent calcination and crushing of the foam gave MgO–Y₂O₃ nanocomposites in the form of thin mesoporous flake‐like powder particles with uniform composition and surface areas of 27–85 m² g ^{? 1}, depending on calcination conditions. The flakes exhibited a homogeneous microstructure comprising intimately mixed nanoscale grains of the cubic MgO and Y₂O₃ phases. This microstructure was resistant to grain coarsening with average grain sizes of less than 100 nm for calcination temperatures of up to 1200°C. The results indicate that the sucrose‐mediated sol–gel process is a simple effective method for making nanoscale mixed oxides.     

Numerical Investigation on Granular Flow from a Wedge‐Shaped Feed Hopper Using the Discrete Element Method

The discharge process of granular material from a wedge‐shaped feed hopper was numerically simulated using a 3D discrete element method. The effects of particle size, feed pipe, side and rear wedge angle on the discharge performance were investigated in terms of flow pattern, discharge rate, and stability. The results show that with larger particle size the granular flow pattern gradually transforms from mass flow to edge flow where the flow rate decreases and the discharging integrity and stability become worse. The presence of the feed pipe reduces the discharge rate and stability. The increase of the feed pipe diameter will diminish the discharge rate and enhance the discharge stability. Both the side and the rear wedge angle have a certain effect on the discharge performance. The effects of feed pipe, side and rear wedge angle on the discharge stability become more significant with larger particle size.     

Two‐step Synthesis of Platelike Potassium Sodium Niobate Template Particles by Hydrothermal Method

Two‐step hydrothermal synthesis of platelike potassium sodium niobate (K, Na)NbO₃ (KNN) template particles was investigated. Platelike K₄Na₄Nb₆O₁₉·9H₂O (KNN‐hydrate) particles were synthesized in 4 mol/L aqueous alkali at 150°C by the sodium dodecyl benzene sulfonate (SDBS) surfactant‐assisted hydrothermal method, which were used as crystal nucleus in the second step of hydrothermal synthesis. The two‐step synthesized KNN‐hydrate particles with 0.6 μm thickness and 7 μm width were prepared at 80°C after 10 h of the second step. After calcination of the KNN‐hydrate particle at 600°C, platelike KNN particles were obtained, which were used as templates for textured ceramics. Particles obtained by the two‐step synthesis showed regular morphology and uniform distribution, with a marked improvement in grain size.     

Low‐Temperature Synthesis of CoNb2O6 Microwave Dielectric Ceramics

Low‐fired cobalt niobate (CoNb₂O₆) microwave dielectric ceramics were prepared through a developed sol–gel process using Nb₂O₅·nH₂O as starting source. A metal‐dioxo‐bridged complex precursor was described on the basis of FT‐IR spectrum. The crystalline phases of calcined powders were characterized by X‐ray diffraction. Nanosized CoNb₂O₆ particles with orthorhombic α‐PbO₂‐type structure were obtained above 750°C. There was no subsequent phase change upon sintering, and all compounds sintered to at least 94% of theoretical density. At 1000°C/4 h, CoNb₂O₆ ceramics exhibited ε_r ~ 21.9, Q × f ~ 66 140 GHz (at 8.9 GHz) and τ_f ~ ?39.7 ppm/°C, having a good potential for low‐temperature cofired ceramic applications.     

Seed‐Free Synthesis and Characterization of Zeolite Faujasite Aluminosilicate Coating on α‐Alumina Supports

NaY zeolite was synthesized by a simple sol–gel technique. NaY zeolite membrane was formed on the alumina substrate using optimized solution composition and synthesis conditions. The formation of the NaY zeolite was ascertained by X‐ray powder diffraction, which showed that the crystallinity improved with annealing. The high‐resolution transmission electron microscopy images of samples annealed at 300°C showed the formation of cubic structure corresponding to NaY zeolite. Brunauer–Emmett–Teller analysis revealed that the synthesized zeolite is a well crystallized NaY zeolite. The SEM images revealed the formation of fine structure NaY zeolite membrane on α‐alumina substrate.     

One‐Pot Synthesis of Submicrometer‐Sized Ce:YAG Spherical Particles by Solvothermal Process Using Alcohol Solvents

A rapid synthesis method for preparing homogeneous and submicrometer‐sized cerium‐doped yttrium aluminum garnet (Ce:YAG) particles was proposed in this work. Instead of precipitating the YAG amorphous precursor prior to the solvothermal process, cerium, yttrium, and aluminum nitrates were dissolved in alcoholic solvents to form transparent and clear solutions that were directly transferred into the stainless autoclave to undergo the solvothermal reaction. Four different alcohol solvents, that is, ethanol, 2‐propanol, 2‐butanol, and tert‐butanol, were used as the reaction medium. The crystallization mechanisms in correlation with the alcohol solvent properties, such as the supercritical point and the dielectric constant, were discussed. The interaction between the alcohol solvent and the precursor salts were also investigated. Well‐dispersed and spherical Ce:YAG particles in size ranging from 200 to 350 nm were obtained in one pot via solvothermal reaction at 285°C from 5 to 8 h.     

Adsorbed O2 on the Graphite‐Induced Growth of Ultra‐Long Single‐Crystalline 6H–SiC Nanowires

Large‐scale ultra‐long 6H–SiC nanowires were in situ synthesized on the as‐prepared SiC–Si ceramic substrate using graphite as the carbon source and substrate as the silicon source via improving the adsorbed O₂ content on the graphite precursors using milling technology. The as‐grown nanowires were typical single crystal of hexagonal 6H–SiC with diameters of 50–100 nm and lengths of up to several millimeters (or even centimeters). Vapor‐solid mechanism was proposed for the growth mode of the as‐grown ultra‐long 6H–SiC nanowires. This study not only provided new insight into the growth mode for in situ synthesizing 6H–SiC nanowires on silicon‐based ceramics, but also suggested a new design methodology for synthesizing ultra‐long nanowires.     

Expanding the Scope of Sortase‐Mediated Ligations by Using Sortase Homologues

Sortase‐catalyzed transacylation reactions are widely used for the construction of non‐natural protein derivatives. However, the most commonly used enzyme for these strategies (sortase A from Staphylococcus aureus) is limited by its narrow substrate scope. To expand the range of substrates compatible with sortase‐mediated reactions, we characterized the in vitro substrate preferences of eight sortase A homologues. From these studies, we identified sortase A enzymes that recognize multiple substrates that are unreactive toward sortase A from S. aureus. We further exploited the ability of sortase A from Streptococcus pneumoniae to recognize an LPATS substrate to perform a site‐specific modification of the N‐terminal serine residue in the naturally occurring antimicrobial peptide DCD‐1L. Finally, we unexpectedly observed that certain substrates (LPATXG, X=Nle, Leu, Phe, Tyr) were susceptible to transacylation at alternative sites within the substrate motif, and sortase A from S. pneumoniae was capable of forming oligomers. Overall, this work provides a foundation for the further development of sortase enzymes for use in protein modification.     

Synthesis of C‐H‐O Symbiosis Networks

The concept of synthesizing carbon, hydrogen, and oxygen (C‐H‐O) SYmbiosis Networks (CHOSYNs) for the design of eco‐industrial parks is introduced. Within a CHOSYN, compounds containing C‐H‐O are exchanged, converted, separated, mixed, and allocated. The use of C‐H‐O as the basis for integration creates numerous opportunities for synergism because C, H, and O are the primary building blocks for many industrial compounds that can be exchanged and integrated. A particularly attractive feature of the CHOSYN framework is its ability to use atomic‐based targets to establish benchmarks for the design of macroscopic systems involving multiple processes. Several structural representations, benchmarking, and optimization formulations are developed to embed potential CHOSYN configurations of interest and to synthesize cost‐effective networks. A case study with several scenarios is solved to demonstrate the new concept and tools. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1242–1262, 2015     

Laccase and Laccase‐Mediated Systems in the Synthesis of Organic Compounds

Laccase, a blue multicopper oxidase, has recently received considerable attention because of its usefulness in oxidizing phenolic and non‐phenolic compounds, as well as its suitability for organic synthesis, environmental pollutant treatment, and other biotechnological applications. This review covers recent studies on the structural properties, occurrence, reaction mechnisms, redox mediators of laccases and their application in organic synthesis procedures, such as dimerization, polymerization, oxidation, and amination. We also present a brief discussion on laccase activity in non‐aqueous media. Given that the development of green protocols for the synthesis of pure compounds is one of the main goals of sustainable chemistry, the exploitation of laccases is expected to remain one of the most popular directions in future biocatalysis research.