Thermochemistry of interaction between cellulose modified with 2-aminomethylpyridine and divalent cations

Cellulose, a biopolymer seemingly inert, was chlorinated initially by reaction with thionyl chloride and then after it becomes more reactive, reacted with 2-aminomethylpyridine molecule for increasing its capacity of removal of divalent cations from an aqueous medium. These materials were characterized by means of elemental analysis, ¹³C NMR, and FTIR techniques, which have proved that a successful modification has occurred. The final material (Celamp), after being characterized was submitted to adsorption assays to evaluate its interaction with cations, whose affinity was found to be Cu²⁺ > Co²⁺ > Ni²⁺ > Zn²⁺. The quantitative cation/base center interactions were calorimetrically determined and showed exothermic enthalpies of ?(13.25 ± 0.12), ?(15.11 ± 0.22), ?(17.23 ± 0.15), and ?(14.66 ± 0.27) kJ mol^?1; negative Gibbs energies of ?(16.3 ± 0.7), ?(14.7 ± 0.7), ?(14.4 ± 0.7), and ?(13.3 ± 0.7) kJ mol^?1; and entropies of 10 ± 2, ?1 ± 1, ?10 ± 1, and ?5 ± 1 J mol^?1 K^?1 for the same sequence of cations. These favorable thermodynamic data suggest that the synthesis involving cellulose produces a new useful material for cation removal from the environment.     

The structure of velutinoside A: a pregnane pentasaccharide from Mandevilla velutina

Detailed spectroscopic analysis (IR, NMR and MS) has shown the structure of the potent bradykinin antagonist velutinoside A to be a pentasaccharide derivative of velutinol A, with the unusual sugars oleandrose and digitalose.     

Synthesis of Dimethoxyfuranonaftoquinones

Recently some furanonaphthoquinones were isolated from Tabebuia species^2,3,4. The structures la, lb2, and li4 were assigned to three of these compounds (those of la and lb being later confirmed by synthesis^3,5,6). However, for the three other isolated compounds the spectroscopic data did not permit a decision to be made between the 2,3,4 - - - 4 isomeric pairs of structure lc and Id, le and lf ³, and lg and lh ⁴. Compounds la, lb, and le (or If), were tested in the KB cell culture assay and shown to be more active cytotoxic agents than lapachol^2,3, the probable biogenetic precursor of all of them.     

High-density nanoparticle ceramic bodies

An investigation on the sinterization of Gd:CeO₂ (Ce_0.85Gd_0.15O_1.9?δ ceramic system) 3–10 nm nanoparticles in pressed bodies was done. The heating rate was taken as a key parameter and two competing sinterization processes were identified, associated with different diffusional mechanisms. Using heating rates of 113 °C min ^?1 , a high-final density (98 % of the theoretical) was obtained by superposing the two aforementioned mechanisms, resulting in a homogeneous microstructure at lower temperatures.     

Acute kidney injury caused by the intraperitoneal injection of Bothrops jararaca venom in rats

Abstract

We examined the ability of Bothrops jararaca venom (12.5?mg/kg) injected intraperitoneally (i.p.) to cause acute kidney injury (AKI) in rats. Blood urea and creatinine (AKI biomarkers, in g dL^?1) were elevated after 2?h in venom-treated rats (urea: from 0.41?±?0.1 to 0.7?±?0.03; creatinine from 46.7?±?3.1 to 85?±?6.7; p?<?0.05; n?=?3 each), with no change in circulating reduced glutathione. Venom-treated rats survived for ～6?h, at which point platelets were reduced (×10³ µL^?1; from 763.8?±?30.2 to 52.5?±?18.2) whereas leukocytes and erythrocytes were slightly increased (from 4.7?±?0.3 to 6.6?±?0.1?×?10³?µL^?1 and from 8.38?±?0.1 to 9.2?±?0.09?×?10⁶?µL^?1, respectively; p?<?0.05); blood protein (5.2?±?0.4?g dL^?1) and albumin (2.7?±?0.1?g dL^?1) were normal, whereas blood and urinary urea and creatinine were increased. All parameters returned to normal with antivenom given 2?h post-envenomation. The i.p. injection of venom caused AKI similar to that seen with other routes of administration.     

Variational transition state theory rate constants and H/D kinetic isotope effects for CH3 + CH3OCOH reactions

The rate constants and H/D kinetic isotope effect for hydrogen abstraction reactions involving isotopomers of methyl formate by methyl radical are computed employing methods of the variational transition state theory (VTST) with multidimensional tunneling corrections. The energy paths were built with a dual-level method using the moller plesset second-order perturbation theory (MP2) method as the low-level and complete basis set (CBS) extrapolation as the high-level energy method. Benchmark calculations with the CBS_D-T approach give an enthalpy of reaction at 0 K for R1 (−4.5 kcal/mol) and R2 (−4.2 kcal/mol) which are in good agreement with the experiment, that is, −4.0 and − 4.8 kcal/mol. For the reactional paths involving the isotopomers CH₃ + CH₃OCOH → CH₄ + CH₃OCO and CH₃ + CH₃OCOD → CH₃D + CH₃OCO, the value of k^H/k^D (T = 455 K) using the canonical VTST/small-curvature tunneling approximation method is 6.7 in close agreement with experimental value (6.2). © 2019 Wiley Periodicals, Inc.     

Effect of lectins from Diocleinae subtribe against oral Streptococci

Surface colonization is an essential step in biofilm development. The ability of oral pathogens to adhere to tooth surfaces is directly linked with the presence of specific molecules at the bacterial surface that can interact with enamel acquired pellicle ligands. In light of this, the aim of this study was to verify inhibitory and antibiofilm action of lectins from the Diocleinaesubtribe against Streptococcus mutans and Streptococcus oralis. The inhibitory action against planctonic cells was assessed using lectins from Canavaliaensi formis (ConA), Canavalia brasiliensis (ConBr), Canavalia maritima (ConM), Canavalia gladiata (CGL) and Canavalia boliviana (ConBol). ConBol, ConBr and ConM showed inhibitory activity on S. mutans growth. All lectins, except ConA, stimulated significantly the growth of S. oralis. To evaluate the effect on biofilm formation, clarified saliva was added to 96-well, flat-bottomed polystyrene plates, followed by the addition of solutions containing 100 or 200 μg/mL of the selected lectins. ConBol, ConM and ConA inhibited the S. mutans biofilms. No effects were found on S. oralis biofilms. Structure/function analysis were carried out using bioinformatics tools. The aperture and deepness of the CRD (Carbohydrate Recognition Domain) permit us to distinguish the two groups of Canavalia lectins in accordance to their actions against S. mutans and S. oralis. The results found provide a basis for encouraging the use of plant lectins as biotechnological tools in ecological control and prevention of caries disease.     

Magnetite colloidal nanocrystals: a facile pathway to prepare mesoporous hematite thin films for photoelectrochemical water splitting

In this study, we demonstrate an alternative and promising way to produce hematite photoanodes with high performance and without the addition of doping or catalytic coating. In this approach, we processed hematite thin films using a colloidal dispersion of magnetite nanocrystals as the precursor. The photoelectrochemical characterization shows that the colloidal approach used to process an undoped hematite photoanode produced a high-performance electrode for water photooxidation with an onset potential as low as 0.8 V(RHE). This value is comparable to the best results reported in the literature for a hematite photoanode modified with catalytic materials. We demonstrate that pure hematite thin films reach 1.1 mA·cm(-2) at 1.23 V(RHE) with back-side illumination.     

Immiscible Newtonian displacement by a viscoplastic material in a capillary plane channel

The immiscible displacement in a capillary plane channel of a Newtonian liquid by a viscoplastic one that obeys a Papanastasiou’s constitutive equation is numerically analyzed. An elliptic mesh generation technique, coupled with the Galerkin finite element method is used to determine the velocity field and the configuration of the interface between the two materials. We investigate the displacement efficiency and the flow patterns of the problem as functions of the dimensionless parameters that govern the problem: the capillary number (Ca), the viscosity ratio of the two fluids (N _η ) and the yield number, (τ′₀). The numerical results showed that for a fixed viscosity ratio, the fraction of mass attached to the wall is a decreasing function of τ′₀. We constructed maps of streamlines in the Cartesian space defined by τ′₀ and Ca for fixed viscosity ratios in order to capture the rough location of bypass and recirculating flow regimes. Higher yield number values induce bypass flow regimes, especially for high Ca. The dimensionless forms of the momentum conservation equation and the force balance at the interface were essential for the understanding of the role played by the dimensionless numbers that govern the problem.     

Residual mass and flow regimes for the immiscible liquid–liquid displacement in a plane channel

The motion of two immiscible liquids in a plane channel is analyzed for the case in which the flow conditions and the interactions between the liquids and the solid surface maintain the displaced fluid attached to the wall. The Galerkin Finite Element Method is used to compute the velocity field and the configuration of the interface between the two fluids. We compare the residual mass fraction left on the wall with its two counterparts in capillary tubes, namely residual mass fraction and dimensionless layer thickness of the displaced fluid. The main result of this comparison was that although there is a qualitative similarity concerning the layer thickness between the two cases, the residual fraction of mass presented an important difference, showing that when the aspect ratio of the capillary passage is large there is an increase in the displacement efficiency. The thickness of the displaced liquid film attached to the channel walls is a function of the capillary number (Ca) and the viscosity ratio (N_μ). A map of streamlines in the Cartesian space (Ca, N_μ) with the different flow regimes of the problem is presented. We also showed that we can adapt the available analytical results obtained for gas-displacement in capillary tubes to the plane channel case, for low values of Ca.