Mechanistic investigations in α‐hydroxycarbonyls reduction by BH4‐

BH₄^‐, a well‐known and widely used reducing agent for carbonyl compounds, has been reported to have the ability to participate in dihydrogen bonding, an interaction with applications in catalysis, stereoselectivity and crystal engineering. Specifically, α‐hydroxycarbonyls are activated for reduction by dihydrogen bonding that occurs between BH₄^‐ and hydroxyl group. We explored the effect of the interaction on the mechanism of these reactions by examining their activation parameters. We found that dihydrogen bonding activates α‐hydroxycyclopentanone for reduction with NBu₄BH₄ by lowering the activation enthalpy by 6.6 kcal/mol. While the activation entropy is a significant component of the barrier, the changes resulting from the occurrence of dihydrogen bonding are manifested predominantly in the enthalpy term. Computational studies suggest that, while internal hydrogen bonding is allowed by the flexibility of the carbon backbone, that interaction is outweighed by dihydrogen bonding once BH₄^‐ is present in the system. Experimentally, a red shift of the hydroxyl frequency is observed upon addition of BH₄^‐ to the reaction mixture, suggesting a dihydrogen bonding interaction. The flexibility of the substrate's skeleton or the selectivity of the hydride sites in BH₄^‐ does not account for the lack of directing effect of the dihydrogen bonding. When a substrate with a rigid naphthalene backbone moiety, 2‐hydroxyacenaphthylen‐1(2H)‐one, is reduced, the stereochemical outcome is very similar to the one corresponding to the α‐hydroxycyclopentanone. Copyright © 2012 John Wiley & Sons, Ltd.     

Controlled dynamics at an avoided crossing interpreted in terms of dynamically fluctuating potential energy curves

The nonadiabatic nuclear wavepacket dynamics on the coupled two lowest (1)Σ(+) states of the LiF molecule under the action of a control pulse is investigated. The control is achieved by a modulation of the characteristics of the potential energy curves using an infrared field with a cycle duration comparable to the time scale of nuclear dynamics. The transition of population between the states is interpreted on the basis of the coupled nuclear wavepacket dynamics on the effective potential curves, which are transformed from the adiabatic potential curves with use of a diabatic representation that diagonalizes the dipole-moment matrix of the relevant electronic states. The basic feature of the transition dynamics is characterized in terms of the notion of the collision between the dynamical crossing point and nuclear wavepackets running on such modulated potential curves, and the transition amplitude is mainly dominated by the off-diagonal matrix element of the time-independent electronic Hamiltonian in the present diabatic representation. The importance of the geometry dependence of the intrinsic dipole moments as well as of the diabatic coupling potential is illustrated both theoretically and numerically.     

The light-activated proton pump Bop I of the archaeon Haloquadratum walsbyi

We have isolated and characterized the light-driven proton pump Bop I from the ultrathin square archaeon Haloquadratum walsbyi, the most abundant component of the dense microbial community inhabiting hypersaline environments. The disruption of cells by hypo-osmotic shock yielded Bop I retinal protein highly enriched membranes, which contain one main 27 kDa protein band together with a high content of the carotenoid bacterioruberin. Light-induced pH changes were observed in suspensions of Bop I retinal protein-enriched membranes under sustained illumination. Solubilization of H. walsbyi cells with Triton X-100, followed by phenyl-Sepharose chromatography, resulted in isolation of two purified Bop I retinal protein bands; mass spectrometry analysis revealed that the Bop I was present as only protein in both the bands. The study of light/dark adaptations, M-decay kinetics, responses to titration with alkali in the dark and endogenous lipid compositions of the two Bop I retinal protein bands showed functional differences that could be attributed to different protein aggregation states. Proton-pumping activity of Bop I during the photocycle was observed in liposomes constituted of archaeal lipids. Similarities and differences of Bop I with other archaeal proton-pumping retinal proteins will be discussed.     

Anti-inflammatory cyclopeptides from the marine sponge Theonella swinhoei

DCCC chromatography followed by HPLC purification on the polar extract of marine sponge Theonella swinhoei resulted in the isolation of five new cyclopeptides, perthamides G–K. The new structures, featuring unprecedented amino acid units, were determined by interpretation of extensive spectroscopic and spectrometric data (MS, ¹H and ¹³C NMR, COSY, HSQC, HMBC, and ROESY). Pharmacological analysis demonstrated that these natural cyclopeptides are endowed with anti-inflammatory potential as assessed by their ability to reduce carrageenan-induced mouse paw oedema.     

Synthesis,solid-state photophysical properties and electropolymerization of novel diazulenyl ethenes

The novel 1,2-di(azulen-1-yl)cyclopent-1-ene 3 was conveniently synthesized via a two-step procedure involving Vilsmeier–Haack acylation of azulene with N,N,N′,N′-tetraethylglutaramide (TEGA) and POCl₃, followed by an intramolecular McMurry coupling of the resulting diketone. In contrast with the previously reported (E)-1,2-di(azulen-1-yl)ethene that shows negligible fluorescence in the solid state, alkene 3 displays fluorescence emission from the S₂ excited state of the azulene moieties. This compound easily polymerizes upon electrochemical oxidation, leading to the formation of a conducting polymer film at the electrode surface.     

Impact of woven fabric: Experiments and mesostructure-based continuum-level simulations

Woven fabric is an increasingly important component of many defense and commercial systems, including deployable structures, restraint systems, numerous forms of protective armor, and a variety of structural applications where it serves as the reinforcement phase of composite materials. With the prevalence of these systems and the desire to explore new applications, a comprehensive, computationally efficient model for the deformation of woven fabrics is needed. However, modeling woven fabrics is difficult due, in particular, to the need to simulate the response both at the scale of the entire fabric and at the meso-level, the scale of the yarns that compose the weave. Here, we present finite elements for the simulation of the three-dimensional, high-rate deformation of woven fabric. We employ a continuum-level modeling technique that, through the use of an appropriate unit cell, captures the evolution of the mesostructure of the fabric without explicitly modeling every yarn. Displacement degrees of freedom and degrees of freedom representing the change in crimp amplitude of each yarn family fully determine the deformed geometry of the mesostructure of the fabric, which in turn provides, through the constitutive relations, the internal nodal forces. In order to verify the accuracy of the elements, instrumented ballistic impact experiments with projectile velocities of 22-550 m/s were conducted on single layers of Kevlar^® fabric. Simulations of the experiments demonstrate that the finite elements are capable of efficiently simulating large, complex structures.     

Detoxification of lignocellulose hydrolysates with ion-exchange resins

Lignocellulose hydrolysates contain fermentation inhibitors causing decreased ethanol production. The inhibitors include phenolic compounds, furan aldehydes, and aliphatic acids. One of the most efficient methods for removing inhibiting compounds prior to fermentation is treatment of the hydrolysate with ion-exchange resins. The performance and detoxification mechanism of three different resins were examined: an anion exchanger, a cation exchanger, and a resin without charged groups (XAD8). A dilute acid hydrolysate of spruce was treated with the resins at pH 5.5 and 10.0 prior to ethanolic fermentation with Saccharomyces cerevisiae. In addition to the experiments with hydrolysate, the effect of the resins on selected model compounds, three phenolics (vanillin, guaiacol, and coniferyl aldehyde) and two furan aldehydes (furfural and hydroxymethyl furfural), was determined. The cation exchanger increased ethanol production, but to a lesser extent than XAD-8, which in turn was less effective than the an ion exchanger. Treatment at pH 10.0 was more effective than at pH 5.5. At pH 10.0, the anion exchanger efficiently removed both anionic and uncharged inhibitors, the latter by hydrophobic interactions. The importance of hydrophobic interactions was further indicated by a substantial decrease in the concentration of model compounds, such as guaiacol and furfural, after treatment with XAD-8.     

Synthesis of Citric Acrylate Oligomer and Its In-Situ Reaction with Chrome Tanned Collagen (Hide Powder)

Summary: The purpose of this study was to formulate the new combined system of acrylic and citric acids, which was prepared by free radical polymerization and esterification reaction at the same time to form citric-acrylate CAC oligomer. The presumable chemical structure of this oligomer and the reaction mechanism were investigated by different spectroscopic tools (¹H,¹³C-NMR and ATR-IR), GPC and TGA/DTA. The effect as masking agent of the eco-friendly oligomer (CAC) in the chrome tanning of the collagen and the pickling of the hide was approached by the study of the hydrothermal and mechanical properties of in-situ treated/grafted chrome tanned collagen (hide powder) and pickled hide, respectively. The use of citric acrylate CAC oligomer instead of the traditional strong acids resulted in significant improvement in chrome exhaustion and physical properties of the leather.     

K18- and CAG-hACE2 Transgenic Mouse Models and SARS-CoV-2: Implications for Neurodegeneration Research

COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is a global pandemic that might lead to very serious consequences. Notably, mental status change, brain confusion, and smell and taste disorders along with neurological complaints have been reported in patients infected with SARS-CoV-2. Furthermore, human brain tissue autopsies from COVID-19 patients show the presence of SARS-CoV-2 neuroinvasion, which correlates with the manifestation of meningitis, encephalitis, leukocyte infiltration, and neuronal damage. The olfactory mucosa has been suggested as a way of entry into the brain. SARS-CoV-2 infection is also known to provoke a hyper-inflammatory reaction with an exponential increase in the production of pro-inflammatory cytokines leading to systemic responses, even in the absence of direct infection of brain cells. Angiotensin-converting enzyme 2 (ACE2), the entry receptor of SARS-CoV-2, has been extensively demonstrated to be present in the periphery, neurons, and glial cells in different brain regions. To dissect the details of neurological complications and develop therapies helping COVID-19 survivors regain pre-infection quality of life, the development of robust clinical models is highly warranted. Several human angiotensin-converting enzyme 2 (hACE2) transgenic mouse models have been developed and used for antiviral drug screening and vaccine development, as well as for better understanding of the molecular pathogenetic mechanisms of SARS-CoV-2 infection. In this review, we summarize recent results from the studies involving two such mouse models, namely K18- and CAG-hACE2 transgenics, to evaluate the direct and indirect impact of SARS-CoV-2 infection on the central nervous system.     

Casorati Inequalities for Statistical Submanifolds in Kenmotsu Statistical Manifolds of Constant ϕ-Sectional Curvature with Semi-Symmetric Metric Connection

In this paper, we prove some inequalities between intrinsic and extrinsic curvature invariants, namely the normalized δ-Casorati curvatures and the scalar curvature of statistical submanifolds in Kenmotsu statistical manifolds of constant ϕ-sectional curvature that are endowed with semi-symmetric metric connection. Furthermore, we investigate the equality cases of these inequalities. We also describe an illustrative example.