Peculiarities of the interaction of dinitrobenzenes witht-BuNHMgBr andt-BuNHLi

Reactions ofm- andp-dinitrobenzenes witht-BuNHMgBr andt-BuNHLi were studied. The reactions afford azo- and azoxy-derivatives and products of nucleophilic substitution.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 739–741, April, 1993.     

Thermal fluctuations of clusters with the long-range interaction

Analysis of surface fluctuation spectra is performed for a large cluster of particles interacting via a sum of the short-range Lennard-Jones potential and long-range ±1/r potential, where the positive sign corresponds to the gravity, and negative corresponds to the electrostatic interaction. The spectral amplitudes of thermally driven capillary modes in a self-consistent field induced by cluster particles including the modes with no axial symmetry are derived in the approximation of small amplitudes. It is demonstrated that within used approximation, the surface tension is independent of the field strength. The low wave vector amplitudes are damped by attracting field that compresses the cluster and magnified by repulsing field leading to cluster fission. The fission threshold is found to be different from that found by Bohr and Wheeler and Frenkel due to the replacement of the ordinary surface tension by the bare one. Molecular dynamics study of a cluster with the long-range interaction in the vapor environment is performed using a novel integrator for a multiscale system. Simulation scheme implies rotation of the long-range components of forces acting on cluster particles thus vanishing an artificial torque. Simulation results justify theoretical conclusion of modes damping and independence of the surface tension of the field strength. Fission threshold evaluated from simulation data is in a good agreement with theory.     

Spectroscopic study of the long-range interaction in saturated heterocycles

The IR and UV spectra of stereoisomeric piperidines and decahydroquinolines were studied, and it was shown that the spectral characteristics (intensity of the long-wavelength Bohlman band of the C-H vibrations, the oscillator strength for the long-wavelength electron transition, etc.) depend on the orientation of the substituents attached to the 2- and 4-ring atoms. The problem of the capacity of the capacity of the p electrons of nitrogen for partial delocalization owing to the interaction with the anticoplanar -C-H bonds is discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1081–1086, August, 1971     

On the Mavroyannis–Stephen relativistic long-range interaction energy term between optically active molecules

The relativistic long-range intermolecular interaction energy term of Mavroyannis and Stephen is estimated for some amino acids by using optical rotatory dispersion data and for hexahelicene by using theoretical values of excitation energies and rotational strengths. The result shows that the interaction energy may be significant for the interaction between some essentially dissymmetric chromophores such as hexahelicene, but that it is unimportant for other cases.     

Stereoselective interaction between DNA and chiral surfaces

ssDNA exhibits much different adsorption behaviors on enantiomer modified surfaces, which can be explained by the stereoselective H-bond interaction between DNA and the chiral surfaces. This effect not only may help to understand the stereospecific cell/substrate interaction and the origin of the chiral preference in nature but also brings novel insights to the study of DNA properties and the application in biochemical devices.     

Effective interaction between charged nanoparticles and DNA

We investigate the effective interaction mediated by salt ions between charged nanoparticles (NPs) and DNA. DNA is modeled as an infinite cylinder with a constant surface charge in an implicit solvent. Monte Carlo simulations are used to compute the free energy of the system described in the framework of the primitive model of electrolytes, which accounts for excluded volumes of salt ions. A mean-field Poisson-Boltzmann theory also allows us to compute the free energy and provides us with explicit formulae for its main characteristics (position and depth of the minimum). We intend here to identify the physical parameters that have a major impact on the NP-DNA interaction, in an attempt to evaluate physico-chemical properties which could play a role in genotoxicity or, which could be exploited for therapeutic use. Thus, we investigate the influence on the effective interaction of: the shape of the nanoparticle, the magnitude of the nanoparticle charge and its distribution, the value of the pH of the solution, the magnitude of Van der Waals interactions depending on the nature of the constitutive material of the NP (metal vs. dielectric). We show that for positively charged concave NPs the effective interaction is repulsive at short distance, so that it presents a minimum at distance from the DNA. This short-range repulsion is specific to indented particles and is a robust property that holds for a large range of materials and charge densities.     

抗坏血酸与DNA相互作用的电化学研究

脱氧核糖酸(DNA)贮存着生物体生命活动的所有信息,这些信息指导着细胞生长、分化、代谢、遗传和变异等重要的生命活动。DNA结构与功能的改变可引起细胞生物学行为的显著改变。DNA与抗癌药物相互作用的研究的报道较多[1,2],而与维生素类药物研究报道相对较少[3]。抗坏血酸(AA)即     

Peculiarities of interaction of dual-band fluorophores with manganese halides

Formation of coordination complexes of DMABA and DMAP with MnHal₂ (Hal = Cl, Br, I) in ethanol is accompanied by a bathochromic shift of the absorption spectra and quenching of the LE and CT fluorescence bands. Complexation of DMABA with MnHal₂ (Hal = F, Cl, Br) in acetonitrile results in enhancement of the LE fluorescence band with no changes in the CT band. The fluorescence rise at the LE band is explained by the blocking of internal conversion in the rigid complex molecule. The complex formation constants have been calculated, and probable structures of the complexes are presented.     

Peculiarities of solvation interaction of water-soluble metallophthalocyanines with ethanol

Physico-chemical characteristics of molecular complexes for water-soluble metallophthalocyanines with alcohol were obtained by the method of thermogravimetric analysis. The change of aggregation state of metallophthalocyanines in aqueous alkaline solutions which is due to the ethanol additions was explained taking into consideration the results of thermogravimetric analysis of metallophthalocyanines crystallosolvates with ethanol.     

Peculiarities of live cells' interaction with micro- and nanoparticles

Experimental evidence collected more than 20 years ago in different laboratories suggests that the interactions between live biological cells and micro- and nanoparticles depend on their metabolic state. These experiments were conducted by reputable groups, led by prominent leaders such as H. Pohl of the USA, who was the inventor of dielectrophoresis, and B. Derjaguin of the Soviet Union who was the leading author of DLVO theory. The experiments had been mostly conducted with microparticles in the early 1980s. In the early 1990s, Ukrainian researchers showed that the interaction of live cells with gold nanoparticles consisted of an initial reversible step that also depended on cell metabolism. They found indirect evidence that the ion pumps of the cells were responsible for the reversible step. Ion pumps generate a transmembrane potential, a measurable and widely-used characteristic of the cell's energetic state. The transmembrane potential, in turn, strongly affects the ζ-potential, as was experimentally discovered 40 years ago by several independent groups using cell electrophoresis. This relationship should be taken into account when DLVO theory is considered as the basis for describing the interactions between live cells and micro- and nanoparticles. Unfortunately, detail theoretical analysis indicates that such modification would not be sufficient for explaining observed peculiarities mentioned above. That is why distinguished theoreticians such as Pohl, Frohlich, Derjaguin and others have suggested three theoretical models, presumably to explain these experiments. These theoretical models should be considered to be complementary to the well-established concepts developed on this subject in the molecular biology of cells and cell adhesion. This paper is not a revision of the existing models. It is an overview of the old and forgotten experimental data and discussion of the suggested theoretical models.The unusual interaction mechanisms are only specific for live biological cells and serve a dual role: either as a first barrier to protect the cell from potentially damaging, dispersed particulates, or as a means of accumulating useful substances. Both functions are critical for the modern problem of nanotoxicology.     

Synchronous fluorescence determination of DNA based on the interaction between methylene blue and DNA

The fluorescence intensity of methylene blue (MB) quenched by DNA in the pH range of 6.5-8.0 was studied with synchronous fluorescence technology. A novel method for detecting single-stranded and double-stranded DNA was developed. The decreased fluorescence intensity at 664 nm is in proportion to the concentration of DNA in the range of 0.28-11.0 μmol L⁻¹ for ctDNA, 0.14-8.25 μmol L⁻¹ for thermally denatured ctDNA and 0.28-8.25 μmol L⁻¹ for hsDNA. The detection limits (S/N = 3) are 0.11, 0.04 and 0.04 μmol L⁻¹, respectively. The method is rapid, selective, and the reagents are lower toxic. It has been used for the determination of DNA in synthetic samples with good satisfaction. In addition, the interaction modes between MB and ctDNA and the mechanism of the fluorescence quenching were also discussed in detail. The experimental results from absorption spectra and fluorescence polarization indicate that the possible interaction modes between MB and DNA are the electrostatic binding and the intercalation binding.     

葛根素与DNA相互作用的光谱法研究

以中性红为光谱探针,采用荧光光谱和紫外-可见光谱法研究了葛根素与DNA的相互作用,考察了离子强度和I-离子浓度对葛根素与DNA作用的影响。结果表明,在生理条件下(pH 7.4),葛根素通过沟槽结合方式与DNA发生作用,DNA对葛根素荧光猝灭属于静态猝灭,测得其结合常数为4.81×104L/mol。     

Spectroscopic studies of the interaction between pirimicarb and calf thymus DNA

The interaction between pirimicarb and calf thymus DNA in physiological buffer (pH 7.4) was investigated with the use of Neutral Red (NR) dye as a spectral probe by UV-vis absorption, fluorescence and circular dichroism (CD) spectroscopy, as well as viscosity measurements and DNA melting techniques. The results revealed that an intercalation binding should be the interaction mode of pirimicarb to DNA. CD spectra indicated that pirimicarb induced conformational changes of DNA. The binding constants of pirimicarb with DNA were obtained by the fluorescence quenching method. The thermodynamic parameters, enthalpy change (ΔHθ) and entropy change (ΔSθ) were calculated to be -52.13±2.04 kJ mol(-1) and -108.8±6.72 J mol(-1) K(-1) according to the van't Hoff equation, which suggested that hydrogen bonds and van der Waals forces might play a major role in the binding of pirimicarb to DNA. Further, the alternative least squares (ALS) method was applied to resolve a complex two-way array of the absorption spectra data, which provided simultaneously the concentration information for the three reaction components, pirimicarb, NR and DNA-NR. This ALS analysis indicated that the intercalation of pirimicarb into the DNA by substituting for NR in the DNA-NR complex.     

Enhancement of the transverse conductance in DNA nucleotides

We theoretically study the electron transport properties of DNA nucleotides placed in the gap between two single-wall carbon nanotubes capped or terminated with H or N. We show that in the case of C-cap and H-termination the current at low electric bias is dominated by nonresonant tunneling, similarly to the cases of gold electrodes. In nitrogen-terminated nanotube electrodes, the nature of current is primarily quasiresonant tunneling and is increased by several orders of magnitude. We discuss the consequence of our result on the possibility of recognition at the level of single molecule.     

Peculiarities of the interaction of ε-caprolactam with the surface of active carbons

The properties of two active carbons before and after the adsorption of ε-caprolactam were studied by IR spectroscopy, XRD analysis, and electron microscopy. It was established that the adsorption of ε-caprolactam from aqueous solutions onto the active carbons is controlled by three types of adsorption interactions: micropore volume filling, hydrogen-bond interaction with functional carboxy groups at the surface of mesopores, and dispersion interaction (leading to the formation of ε-caprolactam aggregates).     

Influence of the long-range coulomb interaction upon the energy spectrum of infinite polyenes

It is shown that the energies of AMO's (E _k ) for an arbitrary homonuclear alternating system can be given with the following expression (identical for AMO with α- and β-spin): $$E_{k\sigma } = \alpha + \tfrac{1}{2}\gamma \pm (\delta ^2 \gamma ^2 + [e_k + \Delta _k (\gamma _{\mu v} )]^2 )^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} {\text{ }}\sigma \in \alpha ,\beta $$ where: e _k are the MO energies, obtained by means of the conventional HF method; δ and Δ _k are correlation corrections depending on the one-center (γ), resp. two-center (γ_{μ v} ) coulomb integrals. By means of the above method, where the interactions between non-adjacent AO's are taken into account, it is shown that the energy gap of an infinite polyene, in the π- electron approximation, is different from zero, regardless of the presence or absence of C-C bond alternation. This means that in adiabatic approximation an infinite atomic chain, satisfying the Born-Karman condition, is not a metal model but a dielectric one.     

Sequence-specific dinucleotide cleavage promoted by synergistic interactions between neighboring modified nucleotides in DNA

Sequence-specific cleavage of DNA by restriction endonucleases has been an indispensable tool in modern molecular biology. However, many potential applications are yet to be realized because of the limited number of naturally available restriction specificities. Efforts to expand this repertoire through protein engineering have met considerable challenges and only brought forth modest success. Taking an alternative approach, we developed a methodology to generate modified DNA susceptible to specific cleavage at selected dinucleotide sequences. This method requires the incorporation of two deoxyribonucleotide analogues by a DNA polymerase: a ribonucleotide and a 5'-amino-2',5'-dideoxyribonucleotide, each of which contains a different base. When linked in a 5' to 3' geometry, the two modified nucleotides act synergistically to promote cleavage at the phosphoramidate linkage, thus providing sequence specificity. Using the transferrin receptor gene as an example, we demonstrate that this dinucleotide cleavage generates discrete DNA fragments that can be either visualized by gel electrophoresis or detected by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.     

Peculiarities of the DNA hybridization on the surface of bilayer lipid membranes

The method of electrostriction was applied to study the peculiarities of interaction of short oligonucleotides with free standing (BLM) and supported lipid membranes (sBLM) and of the duplex formation between complementary oligonucleotides on a membrane surface. The 15-mer single stranded DNA (pentadecathymidylate-(dT)(15)) was modified either with cholesterol (CH(dT)(15)) or by palmitoyl chain (C16(dT)(15)). The interaction of CH(dT)(15) with free standing BLM or with BLM formed on an agar or gold support was accompanied by sharp increase of elasticity modulus in direction perpendicular to the membrane plane ,E( perpendicular), and by increase of surface potential. In contrast, C16(dT)(15) did not induce substantial changes of elasticity modulus, however, the surface potential was changed in a similar manner as for CH(dT)(15). Hybridization of DNA following addition of complementary chain (dA)(15) has been accompanied by a small decrease of elasticity modulus and by a slight increase of surface potential. Both the incorporation of chemically modified oligonucleotides into the lipid bilayer as well as hybridization of DNA are not cooperative processes as has been demonstrated by analysis using Scatchard plot of corresponding values.