Screening the thermal stability of carotenoids-α lactalbumin complex by spectroscopic and molecular modeling approach

Sea buckthorn is a natural food ingredient rich in carotenoids, tocopherols, sterols, flavonoids, lipids, vitamins, tannins and minerals. In this study, we investigated the themostability of the complex formed between α-lactalbumin (α-LA) with carotenoids from sea buckthorn berries extract (CSB) in the temperature range of 25°C to 100°C. The heat induced conformational changes of the α-LA-CSB complex were studied by using fluorescence and molecular modeling techniques. Phase diagram indicated the presence of more than one structurally distinct species as an indicator that temperature influenced the conformation of α-LA. Intrinsic fluorescence studies revealed that carotenoids trapped into the core of α-LA do not bind in locations close to tryptophan (Trp) residues. The synchronous spectra indicated that the interaction between α-LA and CSB had no apparent influence on the local conformation of Trp and tyrosine (Tyr) microenvironments within protein structure. Quenching studies with acrylamide showed that Trp residues had the highest exposure at 80°C, being least accessible to quencher at 60°C. In agreement with the fluorescence spectroscopy observations, the in silico analysis at single molecules level indicated a significant increase of 46.42 Å² and 80.07 Å² of the total accessible surface area of Trp and Tyr residues, respectively with the temperature increase from 25°C to 90°C. Concerning the thermodynamic properties of the α-LA-β-carotene model, the molecular modeling results indicate that the thermal treatment is not favorable for preserving the stability of the complex.     

Asymmetric or symmetric bilayer formation during oblique drop impact depends on rheological properties of saturated and unsaturated lipid monolayers

Bilayer structures are formed by approaching two liquid surfaces with phospholipid monolayers, which are brought into contact by oblique drop impact on a liquid surface. Asymmetric bilayers can be produced by the coupling of drop and target monolayers. In contrast, symmetric bilayers or multilayers are formed by collapse of the compressed target monolayer. We show that under all studied conditions bilayer/multilayer synthesis takes place. The experimental conditions for the synthesis of asymmetric or symmetric bilayers are described quantitatively in terms of the surface rheological (surface elasticity and dilational viscosity) and the hydrodynamical parameters (Weber number and impact angle). The composition and mechanical properties of the phospholipid monolayers strongly influences the patterns of drop impact and the bilayer/multilayer formation. Cholesterol stiffens unsaturated phospholipid monolayers and fluidifies saturated monolayers. All monolayers form asymmetric vesicle-like structures, which are stable in the aqueous medium. Additionally, unsaturated phospholipid monolayers without cholesterol form symmetric vesicles by folding parts of the target monolayer. Sufficient presence of cholesterol in unsaturated phospholipid monolayers inhibits the folding of the target monolayer and the subsequent formation of symmetric bilayers. The rheological properties of saturated and unsaturated phospholipid monolayers and their mixtures with cholesterol are discussed. Based on drop impact results it is shown that the state of a so far undefined region in the DPPC/cholesterol phase diagram is a fluid phase.     

On the correlation between thermal analysis results and corrosion behaviour of some metallic religious artefacts

The aim of this study was to investigate the effects of immersion time on the electrochemical corrosion behaviour of three brass alloys (CuZn) coming from religious artefacts in simulated acid rain at 25 °C, utilising the electrochemical impedance spectroscopy (EIS). The main parameters of the corrosion process were established. On the other hand, the alloys were also analysed by means DSC and TG/DTA before and after immersion in the corrosive environment. Finally, the obtained results were compared in order to correlate them with each other and with the corrosion process.     

Achiral and chiral analysis of duloxetine by chromatographic and electrophoretic methods,a review on the separation methodologies

Duloxetine (DLX) is a widely used antidepressant drug belonging to the class of selective serotonin and norepinephrine reuptake inhibitors (SNRIs); its efficacy has been demonstrated in the treatment of not only major depressive disorders but also diabetic neuropathic pain, generalized anxiety disorder, fibromyalgia or stress urinary incontinence. It is a chiral substance and is used in therapy in the form of the enantiopure S‐DLX, which is twice as active as R‐DLX. Several methods have been published for the achiral and chiral determination of DLX in pharmaceuticals, biological materials and environmental samples, the majority using liquid chromatography and capillary electrophoresis coupled with different detection techniques (UV detection, fluorescence, mass spectrometry). The aim of the current review is to provide a systematic survey of the analytical techniques used for the determination of DLX from different matrices.     

A generalized Schrödinger equation via a complex Lagrangian of electrodynamics

In this paper we give a generalized form of the Schrödinger equation in the relativistic case, which contains a generalization of the Klein-Gordon equation. By complex Legendre transformation, the complex Lagrangian of electrodynamics produces a complex relativistic Hamiltonian H of electrodynamics, on the holomorphic cotangent bundle T′* M. By a special quantization process, a relativistic time dependent Schrödinger equation, in the adapted frames of (T′* M, H) is obtained. This generalized Schrödinger equation can be expressed with respect to the Laplace operator of the complex Hamilton space (T′*M, H). Finally, under some additional conditions on the proper time s of the complex space-time M and the time parameter t along the quantum state, by the method of separation of variables, we obtain two classes of solutions for the Schrödinger equation, one for the weakly gravitational complex curved space M, and the second in the complex space-time with Schwarzschild metric.     

Analysis of mural paintings using in situ non‐invasive XRF,FTIR spectroscopy and optical microscopy

An analytical protocol consisting of X‐ray fluorescence spectroscopy, optical microscopy and Fourier transform infrared spectroscopy was used to study the origin and the nature of the materials (pigments, binders and coating preparation) of the Fundenii Doamnei church mural paint from Bucharest. The main interest of the present study consisted in the original votive paint from narthex, painted in 1757 in a secco technique. During analysis, an unexpected pigment in the votive paint could be detected by the combined analytical techniques: ultramarine blue. Along with this pigment, the presence of gypsum binder based on egg and flax seed oil could also be evidenced. These results demonstrated a secco execution technique of the votive paint and also the presence of a restoration treatment. Moreover, during the present study, the components of the preparation layer and the constitutive pigments from both 1699 and 1757 years mural paints have been analyzed. Hence, the following pigments could be identified: vermilion, azurite, cinnabar, lead white, ochre, natural umber and gold, by using the combination of the analytical techniques. The novelty of our results consists in detecting the composition of the materials used in this church painting (fresco and a secco) during these 254 years since its first restoration. The results of these investigations pointed to the suitability of the non‐destructive and semi‐destructive analytical techniques in the complex characterization of the paints realized in different techniques, at different periods. Copyright © 2013 John Wiley & Sons, Ltd.     

Performance of Pleurotus ostreatus Mushrooms and Spent Substrate for the Biosorption of Cd(II) From Aqueous Solution

The capacities of Pleurotus ostreatus mushroom and spent substrate were evaluated for the biosorption of cadmium (II) from aqueous solution in order to select the most efficient material for bioremediation. The optimum sorption conditions were optimized, including the pH of the aqueous solution, contact time, biomass dosage, initial metal concentration, and temperature. The sorption of cadmium on both biosorbents was also evaluated by several kinetic, equilibrium, and thermodynamic models. The possible heavy metal biosorption mechanisms were evaluated through point of zero charge (pH_pzc), Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy coupled with energy dispersive X-ray microanalysis (SEM-EDX). Based on the results of column studies, the effectiveness of the P. ostreatus spent substrate was confirmed as a biosorbent for Cd(II) removal from aqueous solutions.     

Brown HT

Journal of Thermal Analysis and Calorimetry - Thermal behavior of Brown HT food dye was studied in correlation with the physical and biological antioxidant properties. Brown HT’s structure...     

Magnetic characterization of some nanometric iron oxides

Nanosized magnetite particles embedded in polypyrrole matrix have been studied by Mössbauer and electron magnetic resonance spectroscopy. Comparison with as grown magnetite is made. Hyperfine fields distribution is determined and line shape of resonance curves are discussed in terms of composite structure, sizes and treatments.     

Thermal analysis: an effective characterization method of polyvinyl acetate films applied in corrosion inhibition field

Journal of Thermal Analysis and Calorimetry - To prepare a commercial product with economic and technical relevance, polyvinyl acetate (PVAc) was synthesized, under our laboratory conditions,...