pH- and heat-induced structural changes of bovine α-lactalbumin in response to oleic acid binding

Bovine α-lactalbumin (α-LA) is able to interact with fatty acids, resulting in structural changes that are potentially responsible for the HAMLET/BAMLET role. Different states of α-LA induced by pH, temperature and fatty acid binding have been examined. Evidences of the structural changes of α-LA in molten globule and native states in correlation with oleic acid (OA) binding are shown using fluorescence spectroscopy and in silico approach. In addition, the α-LA was subjected to automated docking analysis, to better understand the interaction with oleic acid, using the PatchDock algorithm. The experimental results demonstrate a more flexible conformation of the protein at pH 2.5 when compared to neutral pH, thus facilitating the oleic acid binding to α-LA. The quenching experiments indicate the remarkable increase in the content of molten globule state at pH 2.5 and a more compact and rigid structure for α-LA–OA complexes at pH 7.0. The docking results are consistent with the experimental data concerning the thermal stability of the α-LA–OA complex. α-LA in different conformations/complexes was sensitive to pH and temperature. Several different molecular species induced by pH, heat treatment and oleic acid binding were suggested. The structure of the protein was more flexible at acidic pH, therefore favoring the hydrophobic exposure.     

Distribution of Mixing Efficiency in a Split-Cylinder Gas-Lift Bioreactor with Immobilized Yarrowia Lipolytica Cells Used for Olive Oil Mill Wastewater Treatment

The distribution of mixing in a split-cylinder gas-lift bioreactor has been investigated for suspensions of immobilized Yarrowia lipolytica cells with particles diameter varying between 3 and 4.2 mm. The results indicated important variation of mixing time on the height of riser or downcomer, as well as different behavior of suspensions flows in these two regions. Therefore, for the riser, the mixing efficiency increases from its bottom to the top, allowing the biocatalyst particles with intermediate size (3.6-mm diameter) reaching the most intense circulation of suspension. The analysis of the suspension flow in the downcomer region revealed that the intermediate positions are associated with the highest mixing mainly for the largest immobilized yeast particles (4.2-mm diameter). In both cases, the influence of aeration on turbulence extent is positive only for air superficial velocity up to 1.05–1.35 × 10^?3 m/s, the magnitude of this effect being correlated with the biocatalyst size and position on the riser or downcomer. By means of the experimental data, mathematical correlations for mixing time have been proposed for each circulation region, taking into consideration both the operational parameters and the distance from the bioreactor bottom. These equations offer a good concordance with the experiment, the average deviation being of 5.82% for the riser and 6.06% for the downcomer zone.     

Coordination‐Assisted Bioorthogonal Chemistry: Orthogonal Tetrazine Ligation with Vinylboronic Acid and a Strained Alkene

Bioorthogonal chemistry can be used for the selective modification of biomolecules without interfering with any other functionality that might be present. Recent developments in the field include orthogonal bioorthogonal reactions to modify multiple biomolecules simultaneously. During our research, we observed that the reaction rates for the bioorthogonal inverse‐electron‐demand Diels–Alder (iEDDA) reactions between nonstrained vinylboronic acids (VBAs) and dipyridyl‐s‐tetrazines were exceptionally higher than those between VBAs and tetrazines bearing a methyl or phenyl substituent. As VBAs are mild Lewis acids, we hypothesised that coordination of the pyridyl nitrogen atom to the boronic acid promoted tetrazine ligation. Herein, we explore the molecular basis and scope of VBA–tetrazine ligation in more detail and benefit from its unique reactivity in the simultaneous orthogonal tetrazine labelling of two proteins modified with VBA and norbornene, a widely used strained alkene. We further show that the two orthogonal iEDDA reactions can be performed in living cells by labelling the proteasome by using a nonselective probe equipped with a VBA and a subunit‐selective VBA bearing a norbornene moiety.     

Cold atoms photoassociation with intense laser pulses

We study the vibrational dynamics produced when two cold atoms are photoassociated in a diatomic molecule by an intense laser pulse (with the duration of hundreds ps), inducing a resonance condition at small interatomic distances. The example analysed is the population transfer from the continuum to the 1_g(6s + 6p_3/2) excited electronic potential of the Cs₂ molecule, at a temperature T ≈ 0.11 mK. We use a non-perturbative treatment by following the wavepackets dynamics on the ground and excited surfaces. We show that cold molecules can be efficiently produced in both ground and excited electronic potentials.     

Investigations on Sweet Cherry Phenolic Degradation During Thermal Treatment Based on Fluorescence Spectroscopy and Inactivation Kinetics

Five anthocyanins were detected in the sweet cherry extract as follows: cyanidin 3-rutinoside, cyanidin 3-glucoside, peonidin 3-rutinoside, peonidin 3-glucoside, and pelargonidin 3-rutinoside, whereas the cyanidin 3-rutinoside was found to be in the highest amount. The effect of thermal treatment on the degradation of the polyphenolic compounds in sweet cherry extract was investigated in the range of 70–120 °C by means of fluorescence spectroscopy and spectrophotometric techniques. The fluorescence spectra were dominated by emission bands with maximum ranging from 356 nm at 25 °C to 350 nm at 110 °C. The heating of sweet cherry extract resulted in structural changes that led to a significant decrease in fluorescence intensity when increasing temperature. Degradation rate constants were estimated using a fractional conversion kinetic model. The activation energy values revealed a higher-temperature dependence of antioxidant activity, followed by anthocyanins, total polyphenols, and total flavonoids.     

Superhydrophobic properties of cotton fabrics functionalized with ZnO by electroless deposition

Cotton fabrics were coated with arrays of ZnO hexagonal prisms using an electroless (catalytic/autocatalytic) deposition process. A typical three step method, similar to those used for electroless deposition of metals on insulating substrates, consisting of pre-activation, activation and deposition steps was employed. The low-dimensional ZnO particles were grown from an aqueous solution containing zinc nitrate as source of zinc ions and dimethylamineborane as reducing agent. The as-obtained ZnO-coated cotton fabrics were characterized from the point of view of structure by X-ray diffraction (XRD) and morphology by scanning electron microscopy (SEM). The XRD studies demonstrate that the ZnO particles have a hexagonal wurtzite crystalline structure. The SEM observations prove that the cotton fibers are homogeneously covered by hexagonal prisms which have uniform base size of approximately 500 nm and height of 1 μm. Optical spectroscopy measurements show that the functionalization with ZnO strongly decreases the transmittance in the UV–vis region of the cotton fabrics. An important characteristic is that the ZnO-functionalized cotton fabrics exhibit superhydrophobicity, with water contact angles exceeding 150°. The technique described is highly reproducible, easy scalable and cheap, allowing a wide range of applications.     

Improvement on Sliding Wear Behavior of Al/Cast Iron Tribopair by CNT's Reinforcement of an Al Alloy

The results presented in this work show the wear characterization of Al-Si matrix composites reinforced by multiwall carbon nanotubes (MWCNTs) under dry reciprocating sliding conditions against a grey cast iron (GCI) The wear resistance is investigated as a function of the carbon nanotube (CNT) content that varied from 2 to 6 wt%. The results demonstrated that the CNT content plays a relevant role in the wear behavior by substantially reducing the wear loss of Al-Si CNT composites. Further, it reduces the wear loss of the grey cast iron counterface. A physical model able to explain the improved behavior in both mating materials is depicted from experimental results.     

Modulation of the antioxidant/pro-oxidant balance,cytotoxicity and antiviral actions of grape seed extracts

Grape seed extracts (GSEs) were investigated in yeast cells harbouring defects in their antioxidant system (regarding the cellular growth and growth recovery from H₂O₂ insult). GSEs antioxidant activity was detected in wild-type and mutant strains Δcta1, Δgsh1 and Δoye2glr1, while pro-oxidant activity in Δsod1 cells was seen. Assessment of proliferation of prostate cancer PC3 and HBV-replicating HepG2 2.2.15 cells treated with GSEs has shown higher cytotoxicity of red grape seed extract (RW) than white grape seed extract (WW) subjective to dose and period of administration. No antiviral effect was detected by measuring the secreted virion particles in HepG2 2.2.15 cells treated with GSEs. The GSEs play a dual antioxidant/pro-oxidant role in vivo according with the cellular antioxidant system deficiencies and exhibit cytotoxic properties in PC3 and HepG2 2.2.15 cell lines, but no antiviral action against HBV.     

Organic–inorganic hybrids obtained by in situ polymerization of aniline in silica/phosphonate matrix

A method for preparing organic–inorganic hybrids containing organophosphorus compounds, silica, and polyaniline (PANI) was developed using sol–gel technique. This method allows the in situ synthesis of organic–inorganic hybrids by reacting tetraethoxysilane (TEOS), aniline, initiator, organophosphorus compound in formic acid. The formic acid has multiple functions: as solvent and acidic media for polymerization of aniline and reagent for sol–gel process. The use of an organophosphorus compound as coupling agent and the introduction of a conductive polymer in silica matrix was investigated.     

Congestion and Fiscal Policy in a Two-Sector Economy with Public Capital: A Quantitative Assessment

This paper analyzes the role of public capital when the services it yields is subject to two forms of congestion, which we characterize as relative and aggregate. We employ a two-sector growth model in which there are conventional profit-maximizing private firms, together with “public firms”, whose objective is to produce a specified quantity of government investment goods – determined by government policy – at minimum cost. We characterize the equilibrium dynamics, and analyze two forms of fiscal disturbances – an increase in public investment, and a decrease in the tax on capital income – by simulating a calibrated economy. We contrast the effects of these two types of congestion on both the existing steady-state equilibrium, as well as for the effectiveness of fiscal policy.