Dihydrogen Adduct (Co–H2) Complexes Displaying H-Atom and Hydride Transfer

The prototypical reactivity profiles of transition metal dihydrogen complexes (M-H₂) are well-characterized with respect to oxidative addition (to afford dihydrides, M(H)₂) and as acids, heterolytically delivering H⁺ to a base and H⁻ to the metal. In the course of this study we explored plausible alternative pathways for H₂ activation, namely direct activation through H-atom or hydride transfer from the σ-H₂ adducts. To this end, we describe herein the reactivity of an isostructural pair of a neutral S= and an anionic S=0 Co-H₂ adduct, both supported by a trisphosphine borane ligand (P₃^B). The thermally stable metalloradical, (P₃^B)Co(H₂), serves as a competent precursor for hydrogen atom transfer to ^tBu₃ArO^⋅. What is more, its anionic derivative, the dihydrogen complex [(P₃^B)Co(H₂)]¹⁻, is a competent precursor for hydride transfer to BEt₃, establishing its remarkable hydricity. The latter finding is essentially without precedent among the vast number of M-H₂ complexes known.     

Combinatorial diversity of fission yeast SCF ubiquitin ligases by homo- and heterooligomeric assemblies of the F-box proteins Pop1p and Pop2p

Background  

SCF ubiquitin ligases share the core subunits cullin 1, SKP1, and HRT1/RBX1/ROC1, which associate with different F-box proteins. F-box proteins bind substrates following their phosphorylation upon stimulation of various signaling pathways. Ubiquitin-mediated destruction of the fission yeast cyclin-dependent kinase inhibitor Rum1p depends on two heterooligomerizing F-box proteins, Pop1p and Pop2p. Both proteins interact with the cullin Pcu1p when overexpressed, but it is unknown whether this reflects their co-assembly into bona fide SCF complexes.     

Thermophoresis of Cylindrical Particle Immersed in Brinkman Fluid

Colloid Journal - This paper reports an analytical study for the thermophoresis of a circular cylindrical aerosol particle embedded in a porous medium of constant porosity based on the Brinkman...     

On the optimization of Gegenbauer operational matrix of integration

The theory of Gegenbauer (ultraspherical) polynomial approximation has received considerable attention in recent decades. In particular, the Gegenbauer polynomials have been applied extensively in the resolution of the Gibbs phenomenon, construction of numerical quadratures, solution of ordinary and partial differential equations, integral and integro-differential equations, optimal control problems, etc. To achieve better solution approximations, some methods presented in the literature apply the Gegenbauer operational matrix of integration for approximating the integral operations, and recast many of the aforementioned problems into unconstrained/constrained optimization problems. The Gegenbauer parameter α associated with the Gegenbauer polynomials is then added as an extra unknown variable to be optimized in the resulting optimization problem as an attempt to optimize its value rather than choosing a random value. This issue is addressed in this article as we prove theoretically that it is invalid. In particular, we provide a solid mathematical proof demonstrating that optimizing the Gegenbauer operational matrix of integration for the solution of various mathematical problems by recasting them into equivalent optimization problems with α added as an extra optimization variable violates the discrete Gegenbauer orthonormality relation, and may in turn produce false solution approximations.     

Formulation of Risperidone as Self-Nanoemulsifying Drug Delivery System in Form of Effervescent Tablets

Risperidone is an atypical antipsychotic drug used to treat schizophrenia. This study aims to formulate risperidone as effervescent tablets to improve patient compliance. Different nanoemulsion combinations were loaded with risperidone to improve its poor water solubility then adsorbed on Aeroperl. The formula showing highest drug dissolution was formulated as effervescent tablets. Factorial design was applied for different tablet formulation variables and the prepared formulae were tested for different criteria in comparison with their corresponding formulae containing drug without nanoemulsion formulation. Statistical analysis was used to determine the most desirable tablet formula considering its Carr index, effervescence time, and drug release.     

Mild Bioconjugation Through the Oxidative Coupling of ortho‐Aminophenols and Anilines with Ferricyanide

Using a small‐molecule‐based screen, ferricyanide was identified as a mild and efficient oxidant for the coupling of anilines and o‐aminophenols on protein substrates. This reaction is compatible with thiols and 1,2‐diols, allowing its use in the creation of complex bioconjugates for use in biotechnology and materials applications.     

Spectroscopic and Molecular Docking Studies of Cu(II), Ni(II), Co(II), and Mn(II) Complexes with Anticonvulsant Therapeutic Agent Gabapentin

New Cu(II), Ni(II), Co(II), and Mn(II) complexes of the gabapentin (Gpn) bidentate drug ligand were synthesized and studied using elemental analyses, melting temperatures, molar conductivity, UV–Vis, magnetic measurements, FTIR, and surface morphology (scanning (SEM) and transmission (TEM) electron microscopes).The gabapentin ligand was shown to form monobasic metal:ligand (1:1) stoichiometry complexes with the metal ions Cu(II), Ni(II), Co(II), and Mn(II). Molar conductance measurements in dimethyl-sulfoxide solvent with a concentration of 10⁻³ M correlated to a non-electrolytic character for all of the produced complexes. A deformed octahedral environment was proposed for all metal complexes. Through the nitrogen atom of the –NH₂ group and the oxygen atom of the carboxylate group, the Gpn drug chelated as a bidentate ligand toward the Mn²⁺, Co²⁺, Ni²⁺, and Cu²⁺ metal ions. This coordination behavior was validated by spectroscopic, magnetic, and electronic spectra using the formulas of the [M(Gpn)(H₂O)₃(Cl)]·nH₂O complexes (where n = 2–6).Transmission electron microscopy was used to examine the nanostructure of the produced gabapentin complexes. Molecular docking was utilized to investigate the comparative interaction between the Gpn drug and its four metal [Cu(II), Ni(II), Co(II), and Mn(II)] complexes as ligands using serotonin (6BQH) and dopamine (6CM4) receptors. AutoDock Vina results were further refined through molecular dynamics simulation, and molecular processes for receptor–ligand interactions were also studied. The B3LYP level of theory and LanL2DZ basis set was used for DFT (density functional theory) studies. The optimized geometries, along with the MEP map and HOMO → LUMO of the metal complexes, were studied.     

A Facile Diversity‐Oriented Multicomponent One‐Pot Synthesis of 3‐Amino‐6,7‐dihydrobenzo[c]thiophen‐4(5H)‐one Derivatives from α‐Oxo‐N,S‐ketene Acetal

A convenient one‐pot multicomponent method for the preparation of 3‐amino‐6,7‐dihydrobenzo[c]thiophen‐4(5H)‐one derivative has been developed. Reaction of 1,3‐cyclohexanedione and phenyl isothiocynate gave α‐oxo‐N,S‐ketene acetal that were reacted in situ with 2‐chloromethylquniazoline‐4‐one derivatives, in the presence of sodium hydride to afford the target compound in reasonable overall yields.     

ZnS nanoparticle synthesis and stability of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) under glow discharge plasma

Ionic liquid glow discharge electrolysis for nanoparticle synthesis is an emerging nanomaterials processing technology and the stability of ionic liquid when they are in contact with plasma is an important issue. This paper discusses the stability of [BMIM][BF4] after exposing this ionic liquid to glow discharge plasma and the synthesis of cubic crystalline ZnS nanoparticles by plasma electrochemical method. Stability of the ionic liquid after plasma exposure to 20 min at 250 V is explained by their FTIR spectra and found that the ionic liquid is stable even after the plasma exposure.     

On the Flame-generated Vorticity Dynamics of Bluff-body-stabilized Premixed Flames

This investigation considers the dynamics of flame-generated vorticity for a premixed, submerged bluff-body stabilized flame. Experimentation characterizes the far-field region in particular with a level of detail not previously afforded to this type of flow. Simultaneous particle imaging velocimetry (PIV), Mie scattering and CH ^? chemiluminescence are used to obtain velocity fields and flame location. Mean static pressure measurements at the combustion chamber wall capture the pressure field. Analysis of the flame fronts in relation to the mean velocity and vorticity fields provides useful insight into the interaction of the flame and the flow. The unique nature of the velocity and vorticity fields and their effect on downstream flame structures are explained by the baroclinic torque generation of vorticity. The coupling that exists among pressure, heat release, and baroclinic generation is acknowledged and will influence strategies for control of the baroclinic mechanism.