[Linear clusters of gold nanoparticles in quasinematic layers of DNA liquid-crystalline dispersion particles].

The effects of small size (approximately 2 nm) gold nanoparticles on the properties of particles of cholesteric liquid-crystalline dispersions formed by double-stranded DNA molecules were analyzed. It has been shown that gold nanoparticles induce two different processes. First, they facilitate reorganization of the spatial cholesteric structure of dispersion particles to nematic one. This process is accompanied by the fast decrease in the amplitude of abnormal band in the CD spectrum. Second, they can form ensembles consisting of gold nanoparticles. This process is accompanied by the development and displacement of surface plasmon resonance band in the visible region of the absorption spectrum. The appearance of this band is analyzed by considering two different models of the formation of ensembles consisting of gold nanoparticles. By small-angle X-ray scattering we performed structural analysis of phases formed by DNA cholesteric liquid-crystalline dispersion particles treated with gold nanoparticles. As a result of this study it was possible to prove the formation of linear clusters of gold nanoparticles in the "free space" between the adjacent DNA molecules fixed in the quasinematic layers of liquid-crystalline particles. It has been hypothesized that the formation of linear clusters of gold nanoparticles is most likely related to DNA molecules, ordered in the spatial structure of quasinematic layers, and the toxicity of these nanoparticles in biological systems hypothesized.

[Structural nucleic acid nanotechnology: liquid-crystalline approach].

The properties of the particles of cholesteric liquid-crystalline dispersions formed by double-stranded DNA molecules obtained as a result of phase exclusion of these molecules from water-salt polymer-containing solutions are briefly described. Physicochemical properties of quasinematic layers of dispersion particles and double-stranded DNA molecules in their content are taken into account in the course of developing fundamental background of the liquid-crystalline approach to the DNA structural nanotechnology. According to different versions of this approach, which is based on intraparticle gelation of cholesteric liquid-crystalline dispersions, spatial structures (DNA nanoconstructions, "rigid" DNA particles) with unique properties, are created. By means of atomic force microscopy images of "rigid" DNA particles of different type are registered. Specific properties of metallic nanoparticles (in particular, gold nanoparticles) are considered while developing the other approach to DNA structural nanotechnology, which provides the basis for "metallized" DNA nanoconstructions.

[Dynamics of penetration of "solid" nanoconstructions based on double-stranded DNA complexed with gadolinium into CHO cells].

Currently, neutron capture therapy is a promising cancer treatment. This method is based on the reaction of the thermal neutron capture by some non-radioactive elements (e.g., Gds57), which results in subsequent emission of electrons and gamma rays. An effective instrument for delivery of gadolinium into the tumor tissue are the particles of the "rigid" nanostructures (NS) based on double-stranded DNA complexes with gadolinium (NS-Gd). The local concentration of Gd in such nanostructures may reach 40%. To optimize the process of neutron capture therapy it is very important to investigate possible penetration mechanisms of NS-Gd particles into the tumor cells. In this work, the dynamics of interaction NS-Gd with cultivated chinese hamster ovary cells (CHO) was studied by confocal and electron microscopy. It is shown that NS-Gd are able to enter CHO cells. This process begins in about 1 hour after the start ofincubation. After 6 h NS-Gd particles were detected in almost all cells. A further increase of the incubation time does not lead to significant changes in cell morphology, although the number NS-Gd inside the cells increases. The plasma membrane of the cells remains intact. The NS-Gd particles, which entered the cells, remain inside the cells for a long time. The data obtained show that NS-Gd are relatively low-toxic and suggest that the presence of NS-Gd in the tumor cells does not prevent their division. The data obtained are important for improving the efficiency of the neutron capture therapy method.

[Bovine sperm chromatin is not protected from the effects ultrasmall gold nanoparticles].

The response of ejaculated bovine spermatozoa to gold nanoparticles was studied by the standard method of nuclear chromatin decondensation in vitro. After the treatment of semen samples with a hydrosol containing gold nanoparticles with an average diameter of 3.0 nm and a concentration of 1 x 10(15) particles/mL, the ability of sperm nuclei to decondense in the presence of sodium dodecyl sulfate (SDS) and dithiothreitol (DTT) dramatically changed compared to the control. The frequencies of gametes with nondecondensed ("intact"), partially decondensed, and completely decondensed nuclei correlated as 40 : 32 : 28% and 0 : 36 : 64% in the experiment and the control, respectively. Moreover, the appearance of a sufficiently large number of gametes with destructed and almost completely destroyed nuclei was noticed in the spermatozoa treated with gold nanoparticles. This article suggests the putative mechanisms of action of ultrasmall gold nanoparticles on the structural and functional integrity of the deoxyribonucleoprotein (DNP) complex of mature male gametes.

[Effect of gold nanoparticles on mouse spermatogenesis].

The response of the mouse male germ cells exposed to gold nanoparticles (approximately 2.5 nm) was studied. Our investigation demonstrates that treatment with Au nanoparticles for four days does not impair the architecture of the spermatogenic epithelium. Cytogenetic evaluation using micronucleus assay showed that gold nanoparticles can affect the chromosomes of early primary spermatocytes. However, gold nanoparticles did not induce chromosome abnormalities in spermatogonial stem cells. Further, the cauda epididymal sperm was isolated on the 14th day after treatment and was incubated in SDS solution (Na sodium dodecyl) and then in a solution containing DTT (dithiothreitol) to induce nuclear chromatin decondensation. Observations showed that after four days of treatment of spermiogenic (postmeiotic) cells with gold nanoparticles the decondensation process had no differences from the control. On the contrary, in the experiment with the same cells and period of fixation but with a single exposure to gold nanoparticles, the number of mature gametes with totally decondensed nuclei reached 100% as opposed to 44% in the controls.

[Liquid-crystalline dispersions formed by complexes of linear double-stranded DNA molecules with dendrimers].

The formation of liquid-crystalline dispersions as a result of interaction of linear, double-stranded DNA molecules with poly(propyleneimine) dendrimers in water-salt solutions was studied. It was shown, that this process does not depend on the ionic strength of solution and molecular structure of dendrimer. By means of the atomic force microscopy, it was established, that in the case of the dendrimer molecules of the 4th generation (G4), the mean size of particles of (DNA-dendrimer G4) liquid-crystalline dispersion is equal to 300-400 nm. The "boundary" conditions (ionic strength of solutionand molecular mass of dendrimer) of formation of optically active (cholesteric) and optically inactive of the (DNA-dendrimer) dispersions were determined using circular dichroism spectroscopy. The interaction of dendrimers of 1st, 2nd, 3rd and 5th generations with DNA molecules results in the obtaining of the optically inactive dispersions. Dendrimer molecules of 4th generation induce the formation of two types dispersions: in solutions of high ionic strength (micro > 0.4) they induce the formation of cholesteric liquid-crystalline dispersions, and in solutions of low or intermediate ionic strength (micro < 0.4) they can form the optically inactive one. The "molecular crowding" affects both the efficiency of binding of dendrimer molecules of 4th generation to DNA, and the mode of spatial packing of (DNA-dendrimer G4) complexes in particles of liquid-crystalline dispersion. The possible reasons capable of explaining the structural polymorphism of (DNA-dendrimer) liquid-crystalline dispersions are discussed.

[From liquid crystals to nanoconstructions of DNA].

This paper reviews data obtained in our Laboratory in the field of the liquid-crystalline dispersions of the double-stranded nucleic acids (DNA, RNA) and results of the analysis of behavior of these biopolymeric molecules in the quasinematic layers. The fundamental data obtained in this area were used as a background for creation of the DNA nanoconstructions, containing different "guest" (biologically active or/and chemical substances) molecules. Two theoretically possible ways for creation of the DNA nanoconstructions were compared. The unique properties of the nanoconstructions dictating the scope of their practical application are described.

[Description of the binding of chitosan to DNA at different ionic strengths in terms of the theories of ion condensation and adsorption].

The binding of chitosan molecules to DNA in solutions of different ionic strength has been studied. The data were analyzed in terms of the model of ion condensation and the thermodynamic theory of the binding of protracted ligands to DNA. Combining these approaches made it possible to estimate the sterical and energetic characteristics of chitosan-DNA binding and establish the dependence of the chitosan-DNA binding constant on the ionic strength of solution.

[Complexes of gadolinium with linear and liquid-crystalline forms of DNA].

The binding of Gd3+ ions to linear double-stranded DNA molecules in water-salt solutions or in liquid-crystalline dispersions is accompanied by sharp changes in their optical and X-ray characteristics. Depending on the initial conditions of complex formation, the binding of Gd3+ ions either to DNA bases or phosphate groups occurs, which leads to changes in the properties of the liquid-crystalline dispersions. The packing of neighboring DNA molecules in particles of the liquid-crystalline dispersion of the complex DNA-Gd3+ depends strongly on the concentration of Gd3+ ions. This process is accompanied by a decrease in the amplitude of Bragg's reflection maximum. The unique properties of the developed material open the possibilities for its practical use.

[Structural polymorphism of the liquid-crystalline dispersions formed from the double-stranded DNA molecules complexed with synthetic polycations].

The double-stranded, linear DNA molecules form the liquid-crystalline dispersions (LCD) in water-salt solutions containing positively charged polyconidin molecules. It was established from the analysis of the absorption spectra of the LCDs formed from (DNA-polyconidin) complexes, that the mean size of the particles of these dispersions is equal to -6000 angstroms. The small-angle X-ray data show, that in the LCD particles different density of packing of the (DNA-polycation) complexes is realized. The comparison of the X-ray data of the liquid-crystalline phases of (DNA-polyconidin) complexes formed under various conditions with the phase diagram, that reflects the polymorphism of the linear double-stranded DNA liquid crystals, demonstrates that the hexagonal mode of the LCD packing is existing in 0.15-0.4 M NaCl solutions, whereas in 0.4-0.55 M NaCl solutions-- the cholesteric one. As a result of specific spatial organization the cholesteric LCD possesses of an abnormal optical activity in the CD spectrum. The similar situation takes place in the case of another synthetic polycation--poly(2,5-ionen), whose chemical structure differs from that of polyconidin. Thus, the structural polymorphism of the (DNA-polyconidine) LCDs was evidenced. It means that change of NaCl concentration opens a gate to control the spatial packing of the molecules of (DNA-polycation) complexes in the particles of LCDs. The supposition about mechanism of formation of the DNA cholesteric liquid-crystalline state in the narrow interval of NaCl concentrations was suggested.

[The thermodynamic stability of nanoconstructions based on the double-stranded DNA molecules].

The temperature stability of nanoconstructions formed by double-stranded DNA molecules fixed in the structure of their liquid crystalline dispersions and cross-linked by nanobridges was determined. It was shown that the heating of nanoconstructions is accompanied by a decrease in the amplitude of the negative bands in the CD spectrum both at lambda approximately 310 and lambda approximately 505 nm. Temperature "melting curves" were derived and characterzed by T(M) values. The T(M) values at lambda approximately 310 and lambda approximately 505 nm coincided with each other but differed from the T(M) value characteristic of the DNA cholesteric liquid crystalline dispersion.

[The interaction between two charged rods in an electrolyte solution]. / Vzaimodeistvie dvukh zariazhennykh sterzhnei v rastvore élektrolita.

A problem on the electrostatic interaction of two homogeneously charged macromolecular rods of a finite length, submerged into an electrolyte solution was considered. An explicit expression for the energy of interaction and rotational moment as a function of the angle of rotation between the long axes of the molecules was obtained. At small angles of rotation, the expression for energy turns into the corresponding formula for parallel rods, and the rotational moment tends to zero, as it follows from geometrical considerations. The possibility is discussed whether the study is applicable to real biological systems, including liquid-crystalline dispersions of DNA.

[DNA liquid-crystalline dispersion particles as a basis for sensitive biosensor elements]. / Chastitsy zhidkokristallicheskikh dispersii DNK kak osnova dlia sozdaniia chuvstvitel'nykh élementov biosensorov.

The data on the morphology, structural parameters, and abnormal optical properties of particles of cholesteric liquid-crystalline dispersions of double-stranded DNA are reviewed. The general principles of the creation and operation of biosensing units based on particles of these suspensions, including dispersed particles immobilized in hydrogels, are described. Examples demonstrating the analytical potentialities of liquid-crystalline biosensing units are given. A method for constructing "sandwich"-type biosensing units based on the particles of liquid-crystalline dispersion formed from molecules of DNA-polycation complexes is described.

[Distribution functions, describing the binding of extended ligands with DNA molecules. Possible use for cases of DNA condensation]. / Funktsiia raspredeleniia, opisyvaiushchaia sviazyvanie protiazhennykh ligandov s molekulami DNK, vozmozhnoe primenenie dlia sluchaia kondensatsii DNK.

Due to noncooperative binding of ligands to DNA molecules, DNA molecules are in equilibrium with different numbers of adsorbed ligands. This equilibrium for a given concentration of the free ligand in the solution is characterized by the distribution function, which describes the probability of revealing the DNA molecule with a definite number of adsorbed ligands. If polycations act as ligands, DNA molecules with the number of ligands sufficient for neutralizing the charges on phosphates may undergo a phase transition. One example of this transition is the formation of liquid-crystalline dispersions during the binding of DNA to chitosan. We analyzed the binding of chitosan to DNA on the assumption that this binding is due to equilibrium adsorption. At a definite concentration of chitosan in solution, DNA molecules are in equilibrium with different numbers of adsorbed molecules of chitosan. If the number of adsorbed ligands exceeds some critical value, the DNA molecule covered with chitosan becomes capable of interacting with other DNA molecules. As a result of this interaction (attraction), liquid-crystalline dispersions can form. Equations describing the dependence of the concentration of DNA molecules on the concentration of the ligand in solution were derived. It was shown that, at given parameters of the model, it is possible to describe experimental data characterizing the formation of cholesteric liquid-crystalline dispersions. The analysis of the data makes it possible to reconstitute both the size of the binding site occupied by chitosan on the DNA and the energy of interaction of chitosan with DNA.

[Thermodynamic models, describing formation of "bridges" between nucleic acid molecules and liquid crystals]. / Termodinamicheskie modeli, opisyvaiushchie obrazovanie "mostikov" mezhdu molekulami nukleinovykh kislot v zhidkikh kristallakh.

Three variants of the model for the formation of "bridges" between the nucleic acid molecules fixed in the structure of particles of liquid-crystalline dispersions were considered. What the three variants have in common is that the bridges represent polymeric chelate cross-links consisting of alternating molecules of daunomycin and copper ions. The differences between the three variants are that in the first variant, the bridges begin and end with daunomycin molecules that form a complex by the mechanism of external binding with nucleic acids; in the second variant, the bridges begin and end with copper ions coupled with the pairs of bases of nucleic acids; and in the third variant, the bridges begin with the daunomycin molecule and end with the copper ion. For each variant, a mathematical model was constructed, which describes the formation of bridges, and equations of binding were derived. The results of calculations were compared with the experimental data. Within the framework of each variant, the values of the energy of interaction between the daunomycin molecule and the copper ion in the bridge, the energy of interaction of the daunomycin molecule with the nucleic acid, and the length of the bridge were varied. For all variants, those values of the parameters were chosen that fit best the experimental data. The theoretical curves obtained using the three variants of the model agree rather well with the family of experimental curves. The best agreement between the theoretical and experimental data was obtained when the polymeric chelate bridge includes more than two daunomycin molecules.

[Molecular construction (superstructures) with adjustable properties based on double-stranded nucleic acids]. / Molekuliarnye konstruktsii (superstruktury) s reguliruemymi svoistvami na osnove dvukhtsepochechnykh nukleinovykh kislot.

Formation of molecular construction that consists of double-stranded molecules of nucleic acids (or synthetic polynucleotides) located at the distance 30-50 A in the spatial structure of particles of their cholesteric liquidcrystalline dispersion and crosslinked by polymeric chelate bridges is described. The resulting superstructure, which possesses peculiar physicochemical properties, could be used as integral biosensor whose properties depend on temperature, the presence of chemical or biologically active compounds of different nature, etc.

["Bridge" structures between nucleic acid molecules fixed in the structure of a liquid crystal]. / "Mostikovye" struktury mezhdu molekulami nukleinovykh kislot, fiksirovannymi v strukture zhidkogo kristalla.

The binding of daunomycin and copper ions to poly(I).poly(C) molecules fixed in a particle of a liquid-crystalline dispersion was studied. A thermodynamic model of adsorption was developed, which makes it possible to describe the formation of complexes of a particular kind, "bridges" that connect adjacent nucleic acid molecules fixed in a liquid crystal. The bridges represent chelate complexes, which incorporate the molecules of the antibiotic daunomycin and copper ions. Equations describing the dependence of the concentration of these bridges in solution on the concentration of their constituents were derived. The family of dependences of experimental amplitudes of bands in CD spectra typical of "bridge" structures on the concentration of copper ions represents a set of S-shaped curves, and, as the concentration of daunomycin in solution increases, the level of saturation of these curves increases. The analysis of experimental data with the use of this model suggests that the structures of this type compete with daunomycin molecules for the binding sites on poly(I).poly(C). By using this model, the energies of formation of bridge structures were calculated.

[Effect of intercalators on the properties of liquid-crystalline dispersions of nucleic acid-chitosan complex]. / Vliianie interkaliatorov na svoistva zhidkokristallicheskikh dispersii kompleksa NK-khitosan.

Molecules of deoxyribonucleic acid and synthetic polydeoxyribonucleotides (NA) in the particles of liquid-crystalline dispersions resulting from interaction with chitosan are accessible to interaction with intercalators. The intercalation is accompanied by alteration in the direction of spatial twist of cholesterics of NA-chitosan complexes. This effect is absent in the case of "classical" cholesterics produced from NA molecules via phase exclusion, i.e., the cholesteric structure of NA-chitosan complex is very "labile" as distinct from "classical" cholesteric NA.

[Some X-ray diffraction parameters of liquid-crystalline dispersions of nucleic acid-chitosan complexes ]. / Nekotorye rentgenograficheskie parametry zhidkokristallicheskikh dispersii kompleksov NK-khitosan.

Liquid-crystalline dispersions of nucleic acid-chitosan complexes (NA-chitosan) possess optical and X-ray diffraction properties different from those of "classical" cholesterics. It is possible that positive charge distribution (distance between charges, chitosan conformation, etc.) in the polymeric chain of chitosan molecule combining with NA molecule is the factor that affects the spatial structure of resulting dispersions.

[Formation of liquid-crystalline dispersions of double-stranded DNA-chitosan complexes]. / Obrazovanie zhidkokristallicheskikh dispersii kompleksov dvukhtsepochechnoi DNK s khitozanom.

Right-handed helical double-stranded DNA molecules were shown to interact with chitosans to form under certain conditions (chitosan molecular weight, content of amino groups, distance between amino groups, ionic strength and pH of solution) cholesteric liquid-crystalline dispersions characterized by abnormal positive band in CD spectrum in the absorption region of DNA nitrogen bases. Conditions were found for the appearance of intense negative band in CD spectrum upon dispersion formation. In some cases, no intense band appeared in CD spectrum in spite of dispersion formation. These results indicate not only the multiple forms of liquid-crystalline dispersions of DNA-chitosan complexes but also a possibility to control the spatial properties of these complexes. The multiplicity of liquid-crystalline forms of DNA-chitosan complexes was attempted to explain by the effect of character of dipoles distribution over the surface of DNA molecules on the sense of spatial twist of cholesteric liquid crystals resulting from molecules of the complexes.