D. A. Faizullin

Interactions of β-lactoglobulin with serotonin and arachidonyl serotonin.

β-Lactoglobulin (β-LG) is a lipocalin, which is the major whey protein of cows milk and the milk of other mammals. However, it is absent from human milk. The biological function of β-LG is not clear, but its potential role in carrying fatty acids through the digestive tract has been suggested. β-LG has been found in complexes with lipids such as butyric and oleic acids and has a high affinity for a wide variety of compounds. Serotonin (5-hydroxytryptamine, 5-HT), an important compound found in animals and plants, has various functions, including the regulation of mood, appetite, sleep, muscle contraction, and some cognitive functions such as memory and learning. In this study, the interaction of serotonin and one of its derivatives, arachidonyl serotonin (AA-5HT), with β-LG was investigated using circular dichroism (CD) and fluorescence intensity measurements. These two ligands interact with β-LG forming equimolar complexes. The binding constant for the serotonin/β-LG interaction is between 10⁵ and 10⁶ M(-1) , whereas for the AA-5HT/β-LG complex it is between 10⁴ and 10⁵ M(-1) as determined by measurements of either protein or ligand fluorescence. The observed binding affinities were higher in hydroethanolic media (25% EtOH). The interactions between serotonin/β-LG and AA-5HT/β-LG may compete with self-association (micellization) of both the ligand and the protein. According to far- and near-UV CD results, these ligands have no apparent influence on β-LG secondary structure, however they partially destabilize its tertiary structure. Their binding by β-LG may be one of the peripheral mechanisms of the regulation of the content of serotonin and its derivatives in the bowel of milk-fed animals.

Structural, biocomplexation and gene delivery properties of hydroxyethylated gemini surfactants with varied spacer length.

Gemini surfactants with hexadecyl tails and hydroxyethylated head groups bridged with tetramethylene (G4), hexamethylene (G6) and dodecamethylene (G12) spacers were shown to self-assemble at the lower critical micelle concentration compared to their conventional m-s-m analogs. The lipoplex formation and the plasmid DNA transfer into different kinds of host cells were studied. In the case of eukaryotic cells, high transfection efficacy has been demonstrated for DNA-gemini complexes, which increased as follows: G6<G4<G12. Different activity series, i.e., G6>G4>G12 has been obtained in the case of transformation of bacterial cells with plasmid DNA-gemini complexes, mediated by electroporation technique. Solely G6 shows transformation efficacy exceeding the control result (uncomplexed DNA), while the inhibitory effect occurs for G4 and G12. Analysis of physico-chemical features of single surfactants and lipoplexes shows that compaction and condensation effects change as follows: G6<G4 ≤ G12, i.e., agree with the order of transfection efficacy, which is supported by membrane tropic properties of G12. On the other hand, gel retardation assay and docking study testify low electrostatic affinity in G12/DNA pair, thereby indicating that hydrophobic effect probably plays important role in the lipoplex formation. Two factors are assumed to be responsible for the inhibition effect of gemini in the case of transformation of bacterial cells. They are (i) an unfavorable influence of cationic surfactants on the electroporation procedure due to depressing the electrophoretic effect; and (ii) antibacterial activity of cationic surfactants that may cause the disruption of integrity of cell membranes.

Novel biomimetic systems based on amphiphilic compounds with a diterpenoid fragment: Role of counterions in self-assembly

Novel biomimetic systems are designed based on cationic surfactants composed of an isosteviol moiety and different counterions, namely bromide (S1) and tosylate (S2). The counterion structure is shown to play a crucial role in the surfactant association. A number of methods used provide evidence that only one type of aggregate, i.e., micelles are observed in the S2 systems, while a concentration-dependent association occurs in the case of S1. The DLS and fluorescence anisotropy measurements reveal that the micelle-vesicle-micelle transitions probably occur with the S1 system. The occurrence of small aggregates near the critical micelle concentration with radii of 2.5 nm is supported by NMR self-diffusion data. The Orange OT solubilization results strongly support the idea of a second threshold in the S1 system around 0.025 mM and provide evidence that hydrophobic domains occur in the aggregates. The latter property and the capacity to integrate with the lipid bilayer make it possible to suggest the newly synthesized surfactants as effective nanocontainers for hydrophobic guests.

Tissue-specific rhamnogalacturonan I forms the gel with hyperelastic properties.

Rhamnogalacturonans I are complex pectin polysaccharides extremely variable in structure and properties and widely represented in various sources. The complexity and diversity of the structure of rhamnogalacturonans I are the reasons for the limited information about the properties and supramolecular organization of these polysaccharides, including the relationship between these parameters and the functions of rhamnogalacturonans I in plant cells. In the present work, on the example of rhamnogalacturonan I from flax gelatinous fibers, the ability of this type of pectic polysaccharides to form at physiological concentrations hydrogels with hyperelastic properties was revealed for the first time. According to IR spectroscopy, water molecules are more tightly retained in the gelling rhamnogalacturonan I from flax fiber cell wall in comparison with the non-gelling rhamnogalacturonan I from primary cell wall of potato. With increase in strength of water binding by rhamnogalacturonan I, there is an increase in elastic modulus and decrease in Poisson’s ratio of gel formed by this polysaccharide. The model of hyperelastic rhamnogalacturonan I capture by laterally interacting cellulose microfibrils, constructed using the finite element method, confirmed the suitability of rhamnogalacturonan I gel with the established properties for the function in the gelatinous cell wall, allowing consideration of this tissue- and stage-specific pectic polysaccharide as an important factor in creation of gelatinous fiber contractility.

Structure and properties of aqueous dispersions of sodium dodecyl sulfate with carbon nanotubes

The dispersing action of the surfactant (sodium dodecyl sulfate, SDS) on the carbon nanotubes (CNT) in aqueous medium has been studied. Electron microscopy, molecular docking, NMR and IR spectroscopies were applied to determine the physical-chemical properties of CNT dispersions in SDS—water solutions. It was established that micellar adsorption of the surfactant on the surface of carbon material and solubilization of SDS in aqueous medium contribute to improving CNT dispersing in water solutions. It was shown that the non-polar hydrocarbon radicals of a single surfactant molecule form the highest possible number of contacts with the graphene surface. Upon increase of the SDS in solution these radicals form micelles connected with the surface of the nanotubes. At the sufficiently high SDS concentration the nanotube surface becomes covered with an adsorbed layer of surfactant micelles. Water molecules and sodium cations are concentrated in spaces between micelles. The observed pattern of micellar adsorption is somewhat similar to a loose bilayer of surfactant molecules.

Chaperone-like activity of β-casein and thermal stability of alcohol dehydrogenase

Correlation between structural peculiarities of beta-casein and its chaperon-like activity was investigated using the recombinant forms of the protein containing the cysteine residues in the polypeptide chain. Aggregation of native and modified forms of β-casein was studied, as well as their chaperon-like activity towards alcohol dehydrogenase thermal aggregation. It has been shown that dimeric and oligomeric forms of β-casein, which are formed due to intermolecular disulfide bonds, significantly differ in their physicochemical and chaperon-like properties from monomeric forms. The thermal stability of alcohol dehydrogenase has been found to depend on the β-casein concentration.

β-casein micelle formation in water-ethanol solutions

36 The molecule of β casein, one of the major milk proteins, is a polypeptide [1] with a charged polar N terminal region and a practically neutral hydrophobic C terminal region, so that it exhibits strong amphiphilic properties [2]. The polypeptide chain of the protein contains numerous unstructured regions [3], which makes β casein a sufficiently flexible mole cule whose peptide and side groups are easily accessi ble for the solvent. In an aqueous solution, β casein exhibits the properties of a surfactant and shows a strong tendency to self association to form spheroidal micelles [3–7]. Caseins are widely used in food pro duction, often in combination with alcohols [8]. The study of self assembly (micelle formation) of β casein in water–alcohol solutions is of fundamental and practical importance, since almost all of the properties of milk are determined by its colloidal structure. Our study of self association of β casein molecules in water–ethanol solutions using dynamic light scatter ing and fluorescence spectroscopy showed the pres ence of two alcohol concentration ranges in which casein undergoes temperature dependent self associ ation. The interpretation of the mechanism of micelle formation is based on the concept of structural micro heterogeneity of water–alcohol solutions.

Structure and catalytic activity of α-chymotrypsin in solutions of gemini surfactants

The regulatory effect of gemini alkylammonium surfactants (GSurf) with the hexamethylene spacer varying in the length of alkyl radicals on the structure and catalytic activity of a-chymotrypsin was studied. A correlation between the activity of a-chymotrypsin and the length of the alkyl radical of GSurf was found. Gemini surfactants enhance the enzyme activity below the critical micelle concentration (CMC) and inhibit that above the CMC. The results of IR spectroscopy and the data on tryptophan fluorescence show that the interaction of GSurf with a-chymotrypsin induces changes in the protein structure differed in intensity. The most probable enzyme complexes with GSurf were characterized by the molecular docking method.

Effect of blood microparticles on the kinetics of polymerization and enzymatic hydrolysis of fibrin

151 Despite the progress made in the diagnosis and treatment of hemostatic disorders, thrombosis remains one of the major causes of morbidity and mortality in developed countries [1]. Fibrin, which is the structural basis of the hemostatic clot (thrombus), is formed from fibrinogen under the influence of thrombin. The result of fibrin polymerization is the formation of fibrin fibers in the form of a branched threeedimensional network, which ensures the mechanical strength of clots and thrombi and their resistance to enzymatic hydrolysis, which is called fibrinolysis [2]. The fibrin network architecture changes depending on pH, concentration of calcium ions, fibrinogen, ionic strength, etc. The activity of thrombin also plays an important role: at low thrombin concentrations, loose fibrin clots consisting of thick fibers are formed, whereas high thrombin concentraa tions ensure the formation of clots consisting of thin, densely packed fibers [3, 4]. The rate of formation of active thrombin, in turn, depends on various factors, including the microvesicles (MVs) entering the blood as a result of activation and/or apoptosis of blood and endothelial cells. Microvesicles are 0.1–1 µm partii cles. The mechanism of their formation ( budding from the outer cell membrane) provides them with procoagulant properties, due to the presence in their composition of anionic phospholipids (which ensure the assembly of tenase and prothrombinase enzyme complexes) and the tissue factor (the most potent actii vator of coagulation) [5]. The vast majority of current studies on MVs are focused on assessing their number and antigenic phenotype as a potential marker of thrombophilia [6]. At the same time, the physiological and pathogenetic role of MVs is not understood comm pletely. In particular, systematic studies of the effect of circulating MVs on the formation and properties of the fibrin clot are absent. The aim of this work was to study the kinetics of fibrinogenesis and fibrinolysis in vitro under the influu ence of MVs produced naturally in the blood of healthy subjects. Preparation of platelettfree plasma (PFP), MVV depleted plasma (MDP) and MVVdepleted plasma supp plemented with kephaline (MDPPK). The blood of 15 healthy donors were taken from the ulnar vein in the morning on an empty stomach, stabilized with 3.8% sodium citrate in the ratio 9 : 1 (vol/vol), and centrifuged twice at 1500g for 15 min and then at 10 000g for 5 min to pellet platelets and obtain PFP. To remove MVs and obtain PFP, …

Lipoplexes of dicationic gemini surfactants with DNA: Structural features of DNA compaction and transfection efficiency

The internal structure of DNA lipoplexes with hydroxyethylated alkylammonium gemini surfactants (GS) with high transfection activity was studied by circular dichroism. It was shown that the efficiency of transfection of HEK293T cells with the pEGFP-N1 circular plasmid was different from zero only in the region of existence of chiral supramolecular DNA-GS complexes and reaches a maximum at concentrations at which the spontaneous aggregation of components is observed.