Chitosan as a removing agent of beta-lactoglobulin from membrane models

Many chitosan biological activities depend on the interaction with biomembranes, but so far it has not been possible to obtain molecular-level evidence of chitosan action. In this article, we employ Langmuir phospholipid monolayers as cell membrane models and show that chitosan is able to remove beta-lactoglobulin (BLG) from negatively charged dimyristoyl phosphatidic acid (DMPA) and dipalmitoyl phosphatidyl glycerol (DPPG). This was shown with surface pressure isotherms and elasticity and PM-IRRAS measurements in the Langmuir monolayers, in addition to quartz crystal microbalance and fluorescence spectroscopy measurements for Langmuir-Blodgett (LB) films transferred onto solid substrates. Some specificity was noted in the removal action because chitosan was unable to remove BLG incorporated into neutral dipalmitoyl phosphatidyl choline (DPPC) and cholesterol monolayers and had no effect on horseradish peroxidase and urease interacting with DMPA. An obvious biological implication of these findings is to offer reasons that chitosan can remove BLG from lipophilic environments, as reported in the recent literature.     

A general nonlinear Fokker-Planck equation and its associated entropy

A recently introduced nonlinear Fokker-Planck equation, derived directly from a master equation, comes out as a very general tool to describe phenomenologically systems presenting complex behavior, like anomalous diffusion, in the presence of external forces. Such an equation is characterized by a nonlinear diffusion term that may present, in general, two distinct powers of the probability distribution. Herein, we calculate the stationary-state distributions of this equation in some special cases, and introduce associated classes of generalized entropies in order to satisfy the H-theorem. Within this approach, the parameters associated with the transition rates of the original master-equation are related to such generalized entropies, and are shown to obey some restrictions. Some particular cases are discussed.     

Pd complexes of iminophosphine ligands: A homogeneous molecular catalyst for Suzuki–Miyaura cross-coupling reactions under mild conditions

The complexes formed by combining Pd(OAc)₂ and iminophosphine ligands (P^N) are active catalysts in Suzuki–Miyaura cross-coupling reactions under mild conditions. Aryl bromides and iodides, as well as benzyl chlorides give the corresponding coupled products in high yields at low temperatures (25–50 °C) using these catalysts. Iminophosphines containing the most sterically demanding groups attached to the N-imino moiety were the most effective ligands. New divalent Pd complexes of known iminophosphines were synthesised and their activity was compared with the in situ generated catalyst system. The complex resulting from the oxidative addition of 4-bromo anisole [Pd(4-CH₃OC₆H₄)Br(P^N)] was more active than the in situ generated system. However, palladacycles containing the iminophosphine ligand (e.g., {[C₆H₄CH(Me)₂St-Bu]Pd(P^N)}⁺PF₆⁻) were less active than the in situ generated catalyst due to the greater stability of the complexes that involve two bidentate ligands. Poisoning tests demonstrated that homogeneous mononuclear palladium species containing the iminophsophine ligand were responsible for the catalytic activity.     

Supercritical extraction of lycopene from tomato industrial wastes with ethane

Supercritical fluid extraction of all-E-lycopene from tomato industrial wastes (mixture of skins and seeds) was carried out in a semi-continuous flow apparatus using ethane as supercritical solvent. The effect of pressure, temperature, feed particle size, solvent superficial velocity and matrix initial composition was evaluated. Moreover, the yield of the extraction was compared with that obtained with other supercritical solvents (supercritical CO? and a near critical mixture of ethane and propane). The recovery of all-E-lycopene increased with pressure, decreased with the increase of the particle size in the initial stages of the extraction and was not practically affected by the solvent superficial velocity. The effect of the temperature was more complex. When the temperature increased from 40 to 60 °C the recovery of all-E-lycopene increased from 80 to 90%. However, for a further increase to 80 °C, the recovery remained almost the same, indicating that some E-Z isomerization could have occurred, as well as some degradation of lycopene. The recovery of all-E-lycopene was almost the same for feed samples with different all-E-lycopene content. Furthermore, when a batch with a higher all-E-lycopene content was used, supercritical ethane and a near critical mixture of ethane and propane showed to be better solvents than supercritical CO? leading to a faster extraction with a higher recovery of the carotenoid.     

Arrowroot starch-based films incorporated with a carnauba wax nanoemulsion,cellulose nanocrystals,and essential oils: a new functional material for food packaging applications

Arrowroot starch (AA)-based films incorporated with a carnauba wax nanoemulsion (CWN), cellulose nanocrystals (CNCs), and essential oils (EOs) from Mentha spicata (MEO) and Cymbopogon martinii (CEO) were produced using the casting technique and then characterized in terms of their water barrier, tensile, thermal, optical, and microstructural properties and in vitro antifungal activity against Rhizopus stolonifer and Botrytis cinerea. Whereas the incorporation of CNCs decreased the moisture content and water vapor permeability of the AA/CWN/CNC film, the additional incorporation of either EO decreased the transparency and affected the microstructure of the AA/CWN/CNC/EO nanocomposites. MEO and CEO incorporation improved the thermal stability of the films and provided excellent protection against fruit-spoiling fungi. Because of their excellent barrier properties against fungal growth, water vapor permeability, and ultraviolet and visible light, these AA/CWN/CNC/EO films have promising potential for application as active food packaging or coating materials.

Graphic abstract

     

Deriving the magnitude of niobium off-center displacement in ferroelectric niobates from infrared spectroscopy

A KSr₂Nb₅O₁₅ nanopowder was synthesized by a chemical route based on a modified polyol method. The nanopowder exhibits the space group P4bm (ferroelectric) ascribed to the displacement of Nb from the central position of an [NbO₆] octahedron, parallel to the c-axis (polarization axis). The magnitude of the niobium off-center, ∆z, was determined by X-ray diffraction and mid-infrared spectroscopy (FTIR). Analysis of the infrared spectrum carried out using curve fitting based on Gaussian functions has revealed a very strong vibration at 413 cm^–1, ascribed to a bond of the Nb off-center with apical oxygen. A classical molecular theory was applied to derive the force constant of this bond from the vibrational frequency. Using the calculus of energies for the wavelength and the harmonic oscillator, we alternatively derived the ∆z parameter.     

Plasticity Effects in the Hole-Drilling Residual Stress Measurement in Peened Surfaces

The incremental hole-drilling technique (IHD) is a widely established and accepted technique to determine residual stresses in peened surfaces. However, high residual stresses can lead to local yielding, due to the stress concentration around the drilled hole, affecting the standard residual stress evaluation, which is based on linear elastic equations. This so-called plasticity effect can be quantified by means of a plasticity factor, which measures the residual stress magnitude with respect to the approximate onset of plasticity. The observed resultant overestimation of IHD residual stresses depends on various factors, such as the residual stress state, the stress gradients and the material’s strain hardening. In peened surfaces, equibiaxial stresses are often found. For this case, the combined effect of the local yielding and stress gradients is numerically and experimentally analyzed in detail in this work. In addition, a new plasticity factor is proposed for the evaluation of the onset of yielding around drilled holes in peened surface layers. This new factor is able to explain the agreement and disagreement found between the IHD residual stresses and those determined by X-ray diffraction in shot-peened steel surfaces.