Interaction between reacetylated chitosan and albumin in alcalescent media.

Interaction of chitosan and its derivatives with proteins of animal blood at blood pH relevant conditions is of a particular interest for construction of antimicrobial chitosan/protein-based drug delivery systems. In this work, the interaction of a series of N-reacetylated oligochitosans (RA-CHI) having M of 10-12 kDa and differing in the degree of acetylation (DA 19, 24, and 40 %) with bovine serum albumin (BSA) in alkalescent media is described in first. It is shown that RA-CHI forms soluble complexes with BSA in solutions with pH 7.

An insight into the effect of interaction with protein on antibacterial activity of chitosan derivatives.

Antimicrobial activity of chitosan in protein-rich media is of a particular interest for various protein-based drug delivery and other systems. For the first time, bacteriostatic activity of chitosan derivatives in the presence of caseinate sodium (CAS) was studied and discussed. Complexation of chitosan derivatives soluble in acidic (CH and RCH) or alkalescent (RCH) media with CAS was confirmed by fluorescent spectroscopy, turbodimetry, light scattering data and measurement of electrical potentials of CAS/chitosan derivative complexes.

Effect of Soft Preheating of Bovine Serum Albumin on the Complexation with Oligochitosan: Structure and Conformation of BSA in the Complex.

Phase analysis, spectroscopic, and light scattering methods are applied to investigate the peculiarities of the interaction of oligochitosan (OCHI) with native and preheated bovine serum albumin (BSA) as well as the conformational and structural changes of BSA in BSA/OCHI complex. As shown, untreated BSA binds with OCHI mainly forming soluble electrostatic nanocomplexes, with the binding causing an increase in BSA helicity without a change in the local tertiary structure and thermal stability of BSA. In contrast, soft preheating at 56 °C enhances the complexation of BSA with OCHI and slightly destabilizes the secondary and local tertiary structures of BSA within the complex particles.

Complexation of oligochitosan with sodium caseinate in alkalescent and weakly acidic media.

Сomplexation of oligochitosan (OCHI) having the degree of acetylation (DA 26 %) with sodium caseinate (SC) at pH 5.8 and 7.2 is described and compared with the complexation of OCHI (DA 2 %) at pH 5.

A feasible approach to tune the interaction of chitosan with sodium dodecyl sulfate.

Interaction of binary chitosan/nonionic surfactant (NIS) system with sodium dodecyl sulfate (SDS) in aqueous solution is described using turbodimetry, light scattering, electophoretic mobility and cryogenic electron microscopy. The formation of insoluble CHI/SDS complexes is weakened with a decrease in molecular weight of chitosan and critical micelle concentration of NIS as well as with an increase in NIS concentration. Soluble chitosan/NIS complexes absorb SDS molecules until the charge of mixed chitosan/NIS/SDS complexes reaches a critical value that depends on chitosan molecular weight followed by aggregation of primary electrostatic complexes via hydrogen bonding to complex nanoparticles.

Molecular features of the interaction and antimicrobial activity of chitosan in a solution containing sodium dodecyl sulfate.

Molecular interaction of chitosan with sodium dodecyl sulfate (SDS) is a more complicated process than it has been imagined so far. For the first time it has been shown that the shorter chitosan chains are, the more preferably they interact with the SDS and the larger-in-size microparticles they form. The influence of ionic strength, urea and temperature on microparticles formation allows interpreting the mechanism of microparticles formation as a cooperative electrostatic interaction between SDS and chitosan with simultaneous decrease in the surface charge of the complexes initiating the aggregation of microparticles.

Genetic Background Underlying 5-HT Receptor Functioning Affects the Response to Fluoxetine.

The influence of genetic background on sensitivity to drugs represents a topical problem of personalized medicine. Here, we investigated the effect of chronic (20 mg/kg, 14 days, i.p.

Sham surgical embryo transfer affects offspring neurodevelopment and manifestation of hypertensive phenotype in ISIAH rats.

The study investigates how surgery during pregnancy, i.e., sham operation associated with embryo transfer, affects hypertensive phenotype in ISIAH rats genetically predisposed to hypertension.

Effect of the Helix-Coil Transition in Bovine Skin Gelatin on Its Associative Phase Separation with Lysozyme.

It is known that the formation of electrostatic polyelectrolyte complexes can induce conformational changes in the interacting macromolecules. However, the opposite effect, namely, that of the helix-coil transition of one of the interacting polyelectrolytes on its associative phase separation with another polyelectrolyte and the possible phase transitions in such systems, has not been determined. Atomic force and confocal laser scanning microscopy, phase analysis, dynamic and electrophoretic light scattering, turbidimetry, absorption, and fluorescence measurements as well as differential scanning calorimetry and rheology were used to study the effect of the helix-coil transition in bovine skin gelatin (Gel) on its associative phase separation with hen egg white lysozyme (Lys) at different temperatures (18-40 °C) and various Lys/Gel weight ratios (0.

On the origin of stretched exponential (Kohlrausch) relaxation kinetics in the room temperature luminescence decay of colloidal quantum dots.

The non-exponential room temperature luminescence decay of colloidal quantum dots is often well described by a stretched exponential function. However, the physical meaning of the parameters of the function is not clear in the majority of cases reported in the literature. In this work, the room temperature stretched exponential luminescence decay of colloidal quantum dots is investigated theoretically in an attempt to identify the underlying physical mechanisms associated with the parameters of the function.

Alteration of the brain morphology and the response to the acute stress in the recombinant mouse lines with different predisposition to catalepsy.

Catalepsy is an inability to correct an externally imposed awkward posture; it is associated with schizophrenia and depression in human. We created new recombinant B6.CBA-D13Mit76C and B6.

Stress and hypertensive disease: adrenals as a link. Experimental study on hypertensive ISIAH rat strain.

Objective: Association between stress and hypertensive disease is still a matter of debate. Can stress be the cause of hypertensive disease and, if so, what mechanisms are involved? To clarify this question, the Inherited stress-induced arterial hypertensive rat strain (ISIAH rat strain) with a stress related arterial hypertension was developed by selection for the enhanced blood pressure response to 0.5 h restraint stress.

Joint aqueous solutions of dextran and bovine serum albumin: coexistence of three liquid phases.

The phase diagram of the system water/dextran (DEX)/BSA was measured as well as modeled. On the experimental side, cloud points were determined and the coexisting phases were analyzed. The theoretical calculations use an approach capable of describing solutions of chain polymers and of globular proteins with the same formalism.

Liquid/gas and liquid/liquid phase equilibria of the system water/bovine serum albumin.

The thermodynamic behavior of the system H2O/BSA was studied at 25 °C within the entire composition range: vapor pressure measurements via head space sampling gas chromatography demonstrate that the attainment of equilibria takes more than one week. A miscibility gap was detected via turbidity and the coexisting phases were analyzed. At 6 °C the two phase region extends from ca.

Effect of protein thermo aggregation on the binding of BSA to gelatin type A.

We study the effect of limited heat-induced aggregation of BSA on structure development in the water-gelatin-thermally aggregated BSA (BSA(TA)) system. The pH is set at 5.4 and the temperature is higher than the conformation transition temperature of gelatin, but lower than the denaturation temperature of BSA.

Macromolecular complexes of BSA with gelatin.

This work studies the effect of the helix-coil transition in gelatin on the structure development in the complex forming water-gelatin-BSA system using dynamic light scattering, environment scanning electron microscopy, rheometry, differential scanning microcalorimetry, circular dichroism, fluorescence, and absorption measurements. It was established that the structure of the complexes formed and the mechanism of intermacromolecular interaction are different in the case of two conformation states of gelatin. Above the temperature of the conformational transition (40 °C) intermacromolecular interaction leads to collapse gelatin macromolecules and formation compact (30 nm in radius) BSA-gelatin complexes (∼6:1, mole/mole), partial stabilization of the secondary structure (increase the mean helix content), and stabilization of BSA molecules against thermo aggregation.

Inducing demixing of semidilute and highly compatible biopolymer mixtures in the presence of a strong polyelectrolyte.

The weak intermacromolecular interactions caused by the presence of a complexing agent in a two-phase biopolymer mixture can affect its phase equilibrium and morphology. In this communication, the attempt was made to induce demixing in semidilute and highly compatible sodium caseinate/sodium alginate system (SC-SA) mixtures in the presence of a sodium salt of dextran sulfate (DSS) at pH 7.0 (above the isoelectrical point of caseins), and to characterize phase equilibrium, intermacromolecular interactions, and structure of such systems by rheo-small angle light scattering (SALS), optical microscopy (OM), phase analysis, dynamic light scattering (DLS), fast protein liquid chromatography (FPLC), ESEM, and rheology.

Phase behavior of aqueous solutions of bovine serum albumin in the presence of dextran, at rest, and under shear.

The demixing conditions for aqueous solutions of bovine serum albumin (BSA, fraction V) and for joint solutions of BSA plus dextran (DEX, M(w) = 2000 kg/mol) were determined by turbidimetric measurements as a function of composition, temperature, and shear rate. Aqueous solutions of BSA phase separate upon heating. Within the region of BSA concentrations between 0.

Interactions and compatibility of 11 S globulin from Vicia faba seeds and sodium salt of carboxymethylcellulose in an aqueous medium.

This work studies specific interactions and compatibility between a legumin and a linear carboxylated polysaccharide using gel permeation chromatography, sedimentation analysis, SDS gel electrophoresis, viscometry and phase analysis measurements. It uses the system water/11 S globulin/CMC as a model. Carboxymethylcellulose (CMC) molecules are able to cause a partial dissociation of the protein, subsequent formation of soluble interbiopolymeric complexes and partial aggregation of the free non combined protein at room temperature and pH 6.

Calorimetric and structural investigation of the interaction between bovine serum albumin and high molecular weight dextran in water.

This work studies specific interactions between a small globular protein and a highly flexible, branched polysaccharide using differential scanning calorimetry (DSC), circular dichroism (CD), fluorescence, and turbidimetry measurements. It uses the system water/bovine serum albumin (BSA)/dextran (D 2000) as a model. Dextran molecules are able to form interpolymeric complexes with BSA in water at both low and high temperatures if the polysaccharide is in excess and if the protein exists in its associated state.

Interfacial tension of aqueous biopolymer mixtures close to the critical point.

Proteins and polysaccharides, being the main constructional materials in many biological structures, have a limited compatibility in aqueous media. At sufficiently high concentrations, they form water-in-water emulsions. Interfacial tension is an important parameter in such systems since it is a controlling factor in the morphology development during processing.

Effect of shear flow on the phase behavior of an aqueous gelatin-dextran emulsion.

A rheo-optical methodology, based on small angle light scattering and transmitted light intensity measurements, has been used to study in situ and on a time resolved basis the shear induced morphology in ternary two-phase water-gelatin-dextran mixtures. Emulsions close to the binodal line as well as far from it have been investigated. It is shown that above a critical shear rate, shear-induced mixing occurs at the length scales probed by the laser light.

Phase state of aqueous gelatin-polysaccharide (1)-polysaccharide (2) systems.

Optical microscopy, ultracentrifugation, phase analysis and turbidimetric titration methods were used to study phase state and phase equilibria of quaternary water-gelatin-pectin-dextran system in the absence of salts and at pH higher than the isoionic point. It was found that these systems are two-phase ones, contrary to the single-phase behaviour of the ternary water-gelatin-pectin and water-gelatin-dextran systems under the same conditions. The observed phase separation is the result of incompatibility of gelatin with pectin, dextran molecules being distributed practically uniformly between coexisting phases.

Phase equilibria and mechanical properties of gel-like water-gelatin-locust bean gum systems.

The establishment of phase equilibrium in aqueous gelatin-locust bean gum (LBG) systems in the process of cooling from 313 to 291 K in specific conditions, passes ahead of the gelation process(.) This allows the suggestion that macrostructure and mechanical properties of the system can be predicted on the basis of knowledge of its phase diagram, obtained for the liquid gelatin-LBG systems comprising gelatin molecular aggregates. Textural and rheological analysis of gel-like gelatin-LBG systems demonstrate the effect of two factors determining their mechanical properties and acting opposite each other when the concentration of LBG in the system increases: concentration of gelatin by LBG in the process of phase separation, and decrease in the density of the gel network.