Green approach for fabrication of bacterial cellulose-chitosan composites in the solutions of carbonic acid under high pressure CO2

The functionalization of the bacterial cellulose (BC) surface with a chitosan biopolymer to expand the areas of possible applications of the modified BC is an important scientific task. The creation of such composites in the carbonic acid solutions that were performed in this work has several advantages in terms of being biocompatible and eco-friendly. Quantitative analysis of chitosan content in the composite was conducted by tritium-labeled chitosan radioactivity detection method and this showed three times increased chitosan loading. Different physicochemical methods showed successful incorporation of chitosan into the BC matrix and interaction with it through hydrogen bonds. Microscopy results showed that the chitosan coating with a thickness of around 10 nm was formed in the bulk of BC, covering each microfibril. It was found that the inner specific surface area increased 1.5 times on deposition of chitosan from the solutions in carbonic acid.

Exploring bioactivity potential of polyphenolic water-soluble lignin derivative

Many natural substances exhibit anti-inflammatory activity and considerable potential in prophylaxis and treatment of allergies. Knowing exact molecular targets, which is required for developing these as medicinal products, is often challenging for multicomponent compositions. In the present study we examined novel polyphenolic substance, a water-soluble fraction of wood lignin (laboratory code BP-Cx-1). In our previous study, a number of polyphenolic components of BP-Cx-1 (flavonoids, sapogenins, phenanthrenes etc.) were identified as the major carriers of biological activity of BP-Cx drug family, and several molecular targets involved in cancer and/or inflammation signaling pathways were proposed based on the results of the in vitro and in silico screening studies. In the present study, half maximal inhibitory concentration (IC50) of BP-Cx-1 was established with a radioligand method and a range of IC50 values between 22.8 and 40.3 μg/ml were obtained for adenosine receptors A1, A2A and prostaglandin receptors EP2, IP (PGI2). IC50 for serotonin 5-HT1 and for glucocorticoid GR receptors were 3.0 μg/ml and 12.6 μg/ml, respectively, both being within the range of BP-Cx-1 concentrations achievable in in vivo models. Further, distribution of [³H] labelled BP-Cx-1 in NIH3T3 murine fibroblasts and MCF7/R carcinoma cells was studied with autoradiography. [³H]-BP-Cx-1 (visualized as silver grains produced by tritium beta particles) was mainly localized along the cell membrane, in the perinuclear region and in the nucleus, suggesting ability of BP-Cx-1 to enter cells and bind to membrane or cytosol receptors. In our experiment, we observed the effect of BP-Cx-1 on maturation of dendritic cells (DCs): downregulation of expression of the lipid-presentation molecule CD1a, co-stimulatory molecules CD80, CD83 and CD 40, decreased production of pro-inflammatory cytokines IL-4 and TNF-α and increased production of anti-inflammatory cytokine IL-10. It is hypothesized that [³H]-BP-Cx-1 detectable in the nucleus is part of the activated GR complex, known to be involved in regulation of transcription of genes responsible for the anti-inflammatory response. Based on IC50, cell distribution data and results of the experiment with DCs it is suggested that the in vivo effects of BP-Cx-1 are mediated via GR and 5-HT1 receptors thus promoting development of tolerogenic effector function in dendritic cells.

Reactive Oxygen Species and low-dose effects of tritium on bacterial cells

The paper continues study of exposures of luminous marine bacteria to low-dose radiation of tritium; tritiated water (HTO) was applied as a source of the irradiation. Hypothesis on involvement of Reactive Oxygen Species (ROS) to signaling mechanism of bacterial cells under exposure to low-intensity tritium radiation was verified. Bacterial bioluminescence intensity was considered as a tested physiological parameter; it was compared to the ROS production in the bacterial environment of different activity concentrations: 0.03, 4.0, and 500 MBq/L. Exposure of the bacteria to chronic low-dose tritium irradiation (<0.08 Gy) increased bioluminescence intensity and ROS production considerably (up to 300%). Spearman rank correlation coefficients were calculated and confirmed relations between the bioluminescence intensity and ROS production. Additional peculiarities of HTO effect were: independence of the bioluminescence intensity and ROS content on HTO activity concentration; low ROS content in bacteria-free aquatic environment. Effects of HTO on bacterial bioluminescence were attributed to: (1) trigger function of tritium decay products in the bacterial metabolic oxygen-dependent processes, with bioluminescence involved; (2) signaling role of ROS as intercellular messengers in "bystander effect"; (3) fixed amount of bacterial cells (3•10⁷ cells/mL) provided the upper limits of the bioluminescence intensity and ROS content. As an outlook, in spite of low energy of tritium decay, its influence on aquatic biota via ROS production by microorganisms should be taken into consideration.

Surface characterization of the thermal remodeling helical plant virus

Previously, we have reported that spherical particles (SPs) are formed by the thermal remodeling of rigid helical virions of native tobacco mosaic virus (TMV) at 94°C. SPs have remarkable features: stability, unique adsorption properties and immunostimulation potential. Here we performed a comparative study of the amino acid composition of the SPs and virions surface to characterize their properties and take an important step to understanding the structure of SPs. The results of tritium planigraphy showed that thermal transformation of TMV leads to a significant increase in tritium label incorporation into the following sites of SPs protein: 41-71 а.a. and 93-122 a.a. At the same time, there was a decrease in tritium label incorporation into the N- and C- terminal region (1-15 a.a., 142-158 a.a). The use of complementary physico-chemical methods allowed us to carry out a detailed structural analysis of the surface and to determine the most likely surface areas of SPs. The obtained data make it possible to consider viral protein thermal rearrangements, and to open new opportunities for biologically active complex design using information about SPs surface amino acid composition and methods of non-specific adsorption and bioconjugation.

Label Distribution in Tissues of Wheat Seedlings Cultivated with Tritium-Labeled Leonardite Humic Acid

Humic substances (HS) play important roles in the biotic-abiotic interactions of the root plant and soil contributing to plant adaptation to external environments. However, their mode of action on plants remains largely unknown. In this study the HS distribution in tissues of wheat seedlings was examined using tritium-labeled humic acid (HA) derived from leonardite (a variety of lignites) and microautoradiography (MAR). Preferential accumulation of labeled products from tritiated HA was found in the roots as compared to the shoots, and endodermis was shown to be the major control point for radial transport of label into vascular system of plant. Tritium was also found in the stele and xylem tissues indicating that labeled products from tritiated HA could be transported to shoot tissues via the transpiration stream. Treatment with HA lead to an increase in the content of polar lipids of photosynthetic membranes. The observed accumulation of labeled HA products in root endodermis and positive impact on lipid synthesis are consistent with prior reported observations on physiological effects of HS on plants such as enhanced growth and development of lateral roots and improvement/repairs of the photosynthetic status of plants under stress conditions.

On the mechanism of biological activation by tritium

The mechanism of biological activation by beta-emitting radionuclide tritium was studied. Luminous marine bacteria were used as a bioassay to monitor the biological effect of tritium with luminescence intensity as the physiological parameter tested. Two different types of tritium sources were used: HTO molecules distributed regularly in the surrounding aqueous medium, and a solid source with tritium atoms fixed on its surface (tritium-labeled films, 0.11, 0.28, 0.91, and 2.36 MBq/cm(2)). When using the tritium-labeled films, tritium penetration into the cells was prevented. The both types of tritium sources revealed similar changes in the bacterial luminescence kinetics: a delay period followed by bioluminescence activation. No monotonic dependences of bioluminescence activation efficiency on specific radioactivities of the films were found. A 15-day exposure to tritiated water (100 MBq/L) did not reveal mutations in bacterial DNA. The results obtained give preference to a "non-genomic" mechanism of bioluminescence activation by tritium. An activation of the intracellular bioluminescence process develops without penetration of tritium atoms into the cells and can be caused by intensification of trans-membrane cellular processes stimulated by ionization and radiolysis of aqueous media.

Effect of tritium on luminous marine bacteria and enzyme reactions

The paper studies chronic effect of tritiated water, HTO, (0.0002-200 MBq/L) on bioluminescent assay systems: marine bacteria Photobacterium phosphoreum (intact and lyophilized) and coupled enzyme reactions. Bioluminescence intensity serves as a marker of physiological activity. Linear dependencies of bioluminescent intensity on exposure time or radioactivity were not revealed. Three successive stages in bacterial bioluminescence response to HTO were found: (1) absence of the effect, (2) activation, and (3) inhibition. They were interpreted in terms of reaction of organisms to stress-factor i.e. stress recognition, adaptive response/syndrome, and suppression of physiological function. In enzyme system, in contrast, the kinetic stages mentioned above were not revealed, but the dependence of bioluminescence intensity on HTO specific radioactivity was found. Damage of bacteria cells in HTO (100 MBq/L) was visualized by electron microscopy. Time of bioluminescence inhibition is suggested as a parameter to evaluate the bacterial sensitivity to ionizing radiation.

Pathways of ion-molecular interactions of nucleogenic phenyl cations with the nucleophilic centers of picolines

Background

The nuclear-chemical method brought unique opportunity for synthesis of unknown and hardly available organic compounds. Presence of tritium labeling allows one-step preparation of radioactive markers for the investigation of chemical and biological processes.

Methods

The ion–molecular reactions of nucleogenic phenyl cations with 4-picoline have been carried out. The phenyl cations were generated by spontaneous tritium β-decay within the tritium-labeled benzene. Both additions to the nitrogen and substitutions about the aromatic ring were able to be studied simultaneously.

Results

Unusual substitutions on both the α- and β-positions of the ring system have been revealed.

Conclusion

By unknown direct phenylation of nitrogen atom tritium-labeled N-phenylpicolinium derivatives, perspective biological markers have been synthesized.

New way of direct nitrogen atom phenylation in quinoline derivatives

Comparison of ion-molecular reactions of free-phenyl cations generated by tritium β -decay with 2-methyl- and 2-phenylquinolines has been investigated. The reaction of direct nitrogen atom phenylation with the help of nucleogenic phenyl cations has been fulfilled for the first time and a new one-step synthesis of tritium-labeled N-phenyl-2-phenylquinolinium salt-lipophilic radioactive biological marker has been elaborated.

[Disordered regions in C-domain structure of influenza virus M1 protein]

Influenza virus matrix M1 protein is one of the main structural components of the virion performing also many different functions in infected cell. X-ray analysis data with 2.08 angstrom resolution were obtained only for the N-terminal part of M1 protein molecule (residues 2-158) but not for its C-terminal domain (159-252). In the present work M1 protein of A/Puerto Rico/8/34 (H1N1) virus strain in acidic solution was investigated with the help of tritium bombardment. Tritium label incorporation into M1 protein domains preferentially labeled the C-domain and inter-domain loops. Analytical centrifugation and dynamic light scattering experiments demonstrated increased hydrodynamic parameters (diameter) that may be explained by low degree of M1 structural organization. Computational analysis of M1 protein by intrinsic disorder predictions methods also demonstrated the presence of unfolded regions mostly in the C-domain and inter-domain loops. It is suggested, that influenza virus M1 polyfunctionality in infected cell is determined by its tertiary structure plasticity which in its turn results from the presence of unstructured regions.

[Effect of tririum on growth and bioluminescence of P. phosphoreum bacteria]

Effect of tritium labeled amino acid valine (0.3-1.0 MBq/ml) on luminous bacteria P. Phosphoreum was studied. The amino acid was used as a nutrient medium for the bacteria. Tritium was found to suppress bacterial growth, but stimulate luminescence: luminescence intensity, quantum yield and time of light-emitting were increased. Activation of the luminescent function is explained by redistribution of electronic density at beta-decay, and affecting biochemical processes in the bacterial media. Effects of alpha- and beta-radiation on luminous bacteria are compared.

[An approach the quantitative determination of the area of glycoprotein spikes at the surface of enveloped viruses]

The density of distribution of glycoproteins on virion surface seriously influences the virus infectivity and pathogenicity. In the present work a method of quantitative determination of the area occupied by the surface glycoprotein spikes is proposed for influenza virus (strain A/PR/8/34) based on data of tritium bombardment and dynamic light scattering (DLS). The method of DLS was used for measuring the diameter of the intact virions and the subviral particles (influenza virions lacking glycoprotein spikes after bromelain digestion). The intact virions and the subviral particles were bombarded by the hot tritium atom flux followed by the analysis of the specific radioactivity of the matrix M1 protein. It was shown that the tritium label was incorporated into the amino acid residues of a thin exposed protein layer and partially penetrated through the lipid bilayer of the viral envelope. As a result, the matrix M1 protein which is located under the lipid bilayer became labeled. The tritium label distribution among different amino acid residues was the same for the M1 protein isolated from the subviral particles and the one isolated from the intact virions. This testifies that the M1 protein spatial structure remains unchanged during proteolysis of the glycoprotein spikes. The difference between the specific radioactivity of the M1 protein isolated from the intact virions and that of the M1 protein isolated from the subviral particles allowed us to calculate the portion of the viral surface which is free of the glycoprotein spikes. If approximate the influenza virion as as here the area occupied by the surface glycoproteins could be calculated. It appeared to be equal to approximately 1.4 yen 10 nm that is about 40% of the total viral surface. This is consistent with the cryoelectron tomography data published for the influenza virus (strain A/X-31). The developed approach could be applied for other enveloped high pathogenic viruses such as HIV and Ebola.

Atomic tritium as an instrument for study of protein behavior at the air–water interface

Atomic tritium was successfully applied as an instrument for study of protein behavior at the air-water interface. Samples of lysozyme solution in 20 mM phosphate buffer (pH 7.0) with concentration of 2 mg/ml incubated at the room temperature for 1 h were exposed to bombardment with tritium atoms generated on hot tungsten wire in special vacuum device. This procedure resulted in substitution of hydrogen atoms by radioactive tritium in the thin surface layer of studied preparations. Analysis of experimental data on intramolecular radioactivity distribution in lysozyme and computer simulation of tritium bombardment allowed us to suggest two equally probable opposite orientations of lysozyme molecule in the adsorption layer at the air-water interface.

Conformational differences between native and recombinant horseradish peroxidase revealed by tritium planigraphy

Significant conformational differences between native and recombinant horseradish peroxidase have been shown by tritium planigraphy, which includes a method of thermal activation of tritium followed by amino acid analysis of the protein preparation. Comparison of radioactivity distribution among the amino acid residues with the theoretical (calculated) accessibility shows that the recombinant enzyme is characterized by high hydrophobicity and compactness of folding. The protective role of oligosaccharides in native enzyme has been confirmed. An unexpected result of the study is a finding on high accessibility of a catalytic histidine residue in solution. An effect of low dose (3 Gy) of irradiation on the accessibility of amino acid residues has been unequivocally demonstrated. The data can be interpreted as swelling of the compact folding and increase in the surface hydrophilicity of the recombinant enzyme. In the case of native enzyme, irradiation does not cause remarkable changes in the accessibility of amino acid residues indicating the possible extensive radical modification of the native enzyme in the life-course of the cell. The catalytic histidine is an exception. It becomes inaccessible after the enzyme irradiation, while its accessibility in the recombinant enzyme increases. An additional observation of a 5-fold decrease in the rate constant towards hydrogen peroxide points to the destructive effect of irradiation on the hydrogen bond network in the distal domain of the native enzyme molecule and partial collapse of the active site pocket.

Studying the spatial organization of membrane proteins by means of tritium stratigraphy: bacteriorhodopsin in purple membrane

The topography of bacteriorhodopsin (bR) in situ was earlier studied by using the tritium bombardment approach [Eur. J. Biochem. 178 (1988) 123]. Now, having the X-ray crystallography data of bR at atom resolution [Proc. Natl. Acad. Sci. 95 (1998) 11673], we estimated the influence of membrane environment (lipid and protein) on tritium incorporation into amino acid residues forming transmembrane helices. We have determined the tritium flux attenuation coefficients for residues 10-29 of helix A. They turned out to be low (0.04+/-0.02 A(-1)) for residues adjacent to the lipid matrix, and almost fourfold higher (0.15+/-0.05 A(-1)) for those oriented to the neighboring transmembrane helices. We believe that tritium incorporation data could help modeling transmembrane segment arrangement in the membrane.

Studying liposomes by tritium bombardment

Bilayer liposomes from a mixture of dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylethanolamine (DPPC: DPPE = 8:2, molar ratio) or DPPC labeled with 14C-DPPC (DPPC: 14C-DPPC) were bombarded with thermally activated tritium atoms. The tritiated liposomes were hydrolyzed by phospholipase C, and the tritium incorporation into different parts of the bilayer along its thickness was determined. The tritium flux attenuation coefficients were calculated for the headgroup (k1 = 0.176+/-0.032 A(-1)) and acylglycerol residue (k2 = 0.046+/-0.004 A(-1)) layers indicating a preferential attenuation of the tritium flux in the headgroup region and relative transparence of the membrane hydrophobic part. The finding is potentially important to apply tritium bombardment for investigation of spatial organization of transmembrane proteins in their native lipid environment.

In situ spatial organization of Potato virus A coat protein subunits as assessed by tritium bombardment

Potato virus A (PVA) particles were bombarded with thermally activated tritium atoms, and the intramolecular distribution of the label in the amino acids of the coat protein was determined to assess their in situ steric accessibility. This method revealed that the N-terminal 15 amino acids of the PVA coat protein and a region comprising amino acids 27 to 50 are the most accessible at the particle surface to labeling with tritium atoms. A model of the spatial arrangement of the PVA coat protein polypeptide chain within the virus particle was derived from the experimental data obtained by tritium bombardment combined with predictions of secondary-structure elements and the principles of packing alpha-helices and beta-structures in proteins. The model predicts three regions of tertiary structure: (i) the surface-exposed N-terminal region, comprising an unstructured N terminus of 8 amino acids and two beta-strands, (ii) a C-terminal region including two alpha-helices, as well as three beta-strands that form a two-layer structure called an abCd unit, and (iii) a central region comprising a bundle of four alpha-helices in a fold similar to that found in tobacco mosaic virus coat protein. This is the first model of the three-dimensional structure of a potyvirus coat protein.

[Differences in the spatial structure of an envelope protein from tobacco mosaic virus and its mutant, detected by tritium planigraphy]

Mutant ts21-66 of the tobacco mosaic virus (TMV) differs from the wild-type TMV-U1 by two mutations (Ile-21-->Thr and Asp-66-->Gly) in the coat protein (CP) gene and in symptoms produced in infected N' plants. The CP structure in TMV-U1 and ts21-66 virions was probed by tritium planigraphy. Compared with the wild-type CP, labeling of the N-terminal region of mutant CP was half as high and suggested its greater shielding. A role of this CP region in virus interactions with the N' resistance system is discussed.

Interaction of tumor and normal blood cells with ethylene oxide and propylene oxide block copolymers

Ethylene oxide and propylene oxide block copolymers (pluronics) are widely known as agents that promote drug penetration across biological barriers. We have studied the interaction of normal and malignant blood cells with pluronics L61 and P85 that have different hydrophobicity. SP2/0 myeloma cells accumulated pluronics while normal cells adsorb most of the polymer on the surface. Interaction of pluronics with cells resulted in drastic changes of membrane microviscosity. Tumor cell membrane microviscosity decreased after pluronics adsorption, in contrast to normal cells, whose membrane microviscosity was enhanced. We suppose that sensitivity of tumor cell membrane microviscosity to the pluronics action correlates with its permeability for molecular substances.

[Regularities of drug desorption from soft contact lenses. 2. In vitro study]

Radiometry of distribution of drugs introduced with soft contact lenses (with 40 and 70% humor content and thickness of 0.2 and 0.7 mm) in the ocular cavity was carried out to compare this mode of drug administration with the traditional methods. The maximal concentrations of the drugs in the anterior chamber humor and in the vitreous body were attained by using saturated highly hydrophilic 0.7 mm thick contact lenses. The drug content in the anterior chamber of the eye upon such a mode of administration was higher than after injection and much higher than after instillation.

[Drug kinetics in soft contact lenses. I. In vitro studies]

The in vitro kinetics (specifically, absorption and desorption) of drugs belonging to various pharmacological groups (atropine sulfate, gentamicin sulfate, dexamethasone, lecozyme, and poludan) in soft contact lenses (low-hydrophilic with 40% aqueous content and highly hydrophilic with 74% aqueous content. 0.2 and 0.7 mm thick) was studied by radiometry, as were the effects of chemical structure of a drug, hydrophilic properties and thickness of soft contact lenses, and temperature of solution on these processes.

[Study of the spatial structure of globular proteins by tritium planigraphy. Short peptides as a model of a fully extended polypeptide chain]

The interaction of tritium atoms with amino acid residue from short peptides was studied. The short peptides were considered as a model of extended polypeptides chain. Every residue in this chain has 100% steric accessibility. It was shown that: 1. The linear correlation exists between the residue accessible surface area (that is composed of hydrocarbon fragments) and the amount of tritium interacting with this residue; 2. The presence of the tertiary carbon atom in the residue side chain influences on the reactivity of this residue; 3. The N- or C-terminal residue presence does not influences on the possibility of interaction of this residue with tritium atoms. The obtained reactivity scale of amino acid residues is compared with other theoretical and experimental data.

Homogeneous solutions of hydrophilic enzymes in nonpolar organic solvents. New systems for fundamental studies and biocatalytic transformations

A typical hydrophilic enzyme, CT, can be dissolved in nonpolar organic solvents (n-octane, cyclohexane and toluene) up to microM concentrations. In the homogeneous solution obtained, the enzyme possesses catalytic activity and enormously high thermostability. It does not lose this activity even after several hours refluxing in octane (126 degrees C) or cyclohexane (81 degrees C).

[Spatial organization of cytochrome oxidase subunit II]

We have studied the tryptic digestion and cyanogen bromide cleavage of the tritium-labelled subunit II from bovine cytochrome oxidase. Basing on the radioactivity distribution in the peptides obtained we suggest a model for the spatial structure of the title subunit.