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Polymer Science Series C

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ISSN (Print) 1555-614X - ISSN (Online) 1811-2382
Published by Springer-Verlag

[2216 journals]

Complexes of nucleic acids with oppositely charged amphiphilic ions in aqueous and organic solutions
- Abstract: Abstract The published data on the interaction of DNA macromolecules with cationic amphiphiles (surfactants) are analyzed. The effect of the structure of surfactant molecules on their interaction with DNA and the structure of DNA-surfactant complexes is examined. The unique property of DNA molecules to preserve the double-helix conformation in complexes is considered. The structure of DNA-surfactant complexes in aqueous and organic solutions is discussed, and examples of the possible application of these complexes are presented.
  PubDate: 2012-09-01
Comparative properties of hyaluronan and chitosan in aqueous environment
- Abstract: Abstract In this paper, our objective is to compare the physico-chemical properties of chitosan (CHIT) and hyaluronic acid (HA), two important polysaccharides often used in biomedical or cosmetic applications. Polymer-polymer interactions as well as polymer-solvent interactions, studied by experiments and by molecular modeling, are discussed for the two biopolymers in presence of aqueous environments. HA and CHIT have similar non-freezing water content, although HA retains more water than CHIT at large degree of relative humidity (RH). Thermal degradation is larger for HA. The specific viscosity at zero shear rate of CHIT deviates from the master curve, whereas that of HA superimposed nicely. The solution viscosity of concentrated solutions of CHIT continuously decreases in the shear rate range between 0.5 up to 100 s−1, whereas HA shows a Newtonian plateau at low shear rates. Dynamic rheology of semi-diluted solutions of HA shows storage modulus G′ lower than the loss modulus G″ up to 30 g/L but that of CHIT at 20 g/L shows G′ > G″ at nearly the same overlap parameter. The viscosity of CHIT solution is less influenced by temperature than that of HA. These results clearly underline the importance of interchain interactions for CHIT in a good solvent. Molecular modelling is used to provide insights on both the aggregated state and solution state of the two polysaccharides. Interchain interactions in the organized models were predicted larger for CHIT than for HA whereas the interaction between the polysaccharide and the solvent molecules are larger for HA than for CHIT. This approach rationalizes the experimental observations: the higher solvation of HA and the higher ability to aggregate for CHIT.
  PubDate: 2012-09-01
DNA-polymer complexes for gene therapy
- Abstract: Abstract The condensation of DNA induced by vinyl saccharide graft copolymers of N-methacryloy-lamino-D-glucose with N,N-dimethylaminoethyl methacrylate and N-vinylpyrrolidone with N-vinylamine and induced by the linear polycation poly(L-lysine) in solution, as well as the conformational changes of a DNA molecule during its interaction with polycations in solution, is studied by atomic-force microscopy, low-gradient viscometry, dynamic birefringence, spectrophotometry, circular dichroism, and electrophoresis. The differences in the conformational changes of DNA related to the effect of polycations and other agents inducing its condensation are discussed.
  PubDate: 2012-09-01
Aggregation effects in solutions of model oligopeptides and other amphiphilic polymers
- Abstract: Abstract The problems of the aggregation behavior of amphiphilic macromolecules in solution are discussed. The cases of electrically neutral and polyelectrolyte chains are examined. The effect of chain parameters, interaction parameters, and external factors—temperature, solvent quality, medium pH, and solution ionic strength—on the structure and stability of the aggregates is analyzed. As examples, two systems are selected: (i) a solution of model oligopeptides with different chain architectures that contain hydrophobic alanine and negatively charged polar aspartic acid and (ii) a solution of HP copolymers in which hydrophobic (H) groups are located in the backbone and polar (P) side groups have a rigid bond to the backbone. The micelles formed by the oligopeptides are thermodynamically stabilized after the addition of a univalent salt; in addition, the effect heavily depends on the pH of a medium and the size of the added cations. For the second system, the regions of stability of aggregates of different geometries are determined and the corresponding phase diagram is constructed as a function of the surface tension and bending modulus of the surface of the aggregate. The problems related to the kinetics of coalescence of the aggregates are discussed.
  PubDate: 2012-09-01
Chiral selection in supercoiling and wrapping of DNA
- Abstract: Abstract This paper gives an account of our recent studies on the mechanisms for chiral selection in super-coiling and wrapping of DNA. We first present a compact model of double-stranded DNA (Model 1), which consists of two elastic chains that mutually intertwine in a right-handed manner to form a double-stranded helix. Numerical analysis of this model suggests an intrinsic propensity of DNA to writhe in the left direction upon bending. Based on this asymmetric elasticity of DNA, we present a further simplified model of DNA (Model 2), which is a single-chained homopolymer with the propensity to writhe in the left direction upon bending. This simplified model is incorporated into a Langevin dynamics study to explore the origin of the uniform left-handed wrapping of DNA around a nucleosome core particle in nature. We finally show that the propensity of DNA to writhe in the left direction upon bending gives rise to the selective left-handed wrapping, provided that the size of the core particle is appropriate. This result suggests the fundamental significance of the asymmetric elasticity of helical biopolymers in their structural dynamics and functions.
  PubDate: 2012-09-01
Templating of inorganic nanomaterials by biomacromolecules and their assemblies
- Abstract: Abstract During the past decade biomacromolecules attracted tremendous attention as versatile materials for self-assembly, nanoconstruction, and templating. An increasing number of reports highlights creative applications of DNA, proteins, and their assemblies for construction of materials, which synthesis by traditional top-down techniques is not possible. This review summarizes various aspects of the application of biomacromolecules and their self-organized structures for building-up inorganic nanomaterials of different complicity by metallization or mineralization of natural templates. The central focus of the review is given to DNA-templated and DNA-directed synthesis of nanostructures, as the progress in the utilization of DNA for nanoconstruction is most considerable.
  PubDate: 2012-09-01
Nanomaterials based on peptides
- Abstract: Abstract Owing to the assortment of functional groups, peptides are capable of self-assembly and formation of regularly patterned supramolecular complexes. Peptide-based nanomaterials offer promise for medicine, engineering, and bioimaging. The present review surveys the structure and characteristics of filaments formed by peptides of various secondary structures and their further assembly into 2D and 3D nanomaterials. Possible application areas of self-assembling peptide systems, including the synthesis of inorganic nanomaterials, are considered.
  PubDate: 2012-09-01
How two meters of DNA fit into a cell nucleus: Polymer models with topological constraints and experimental data
- Abstract: Abstract A recent experiment has confirmed the theoretical prediction of the fractal properties of DNA packaged in the cell nucleus of eukaryotes, particularly in interphase chromosomes. In this study, both the main theoretical ideas and the experimental results are presented in a compact form. Other properties of chromosomes, that is, the so-called territories, which allow for a natural explanation through the concepts of polymer physics, are discussed. At the end, some open questions are formulated.
  PubDate: 2012-09-01
Compaction of DNA in solutions of highly charged proteins carrying the same charge as DNA
- Abstract: Abstract The theory of DNA compaction in solutions of highly charged proteins carrying charge of the same sign as DNA is developed. It is shown that the introduction of a negatively charged protein may induce the collapse of DNA that occurs as a first-order phase transition. The concentration of protein in the vicinity of DNA practically coincides with the concentration of protein in solution on the whole, and the introduction of protein into a solution is equivalent to the effective worsening of solvent quality. The higher the absolute value of the protein charge, the more pronounced this worsening. The higher the charge of the protein, the smaller its content that causes the compaction of DNA. The properties of the transition depend on the effective charge of DNA and on the concentration of a low-molecular-mass salt. An increase in the concentration of the salt may weaken the action of protein as a compaction agent and cause the reverse transition of a DNA macromolecule to the coiled state.
  PubDate: 2012-09-01
Synthesis of poly(N,N-dimethylaminoethyl methacrylate) nanogels in reverse micelles for delivery of plasmid DNA and small interfering RNAs into living cells
- Abstract: Abstract Hydrogel nanoparticles of poly(N,N-dimethylaminoethyl methacrylate) with hydrodynamic radii of 40–50 nm are synthesized via the copolymerization of a water-soluble monomer and N,N′-methylenebis(acrylamide) in a solution of Brij-97 reverse micelles in cyclohexane. All amino groups of nanoparticles are protonated in a weakly acidic solution; however, almost one-third of them remain inaccessible to a flexible polystyrenesulfonate polyanion, while almost two-thirds of them remain inaccessible to rigid double-helical DNA. Complexes of nanogels with plasmid DNA carrying the firefly luciferase gene transfect eukaryotic cells in a cultural medium, and the products of interaction of nanogels with small interfering RNAs suppress expression of the marker enzyme. In both systems, the replacement of linear polyamine with nanogel significantly increases the efficiency of delivery. The activity of nanogels in transfection experiments depends in an extremum pattern on the crosslink degree and achieves a maximum value at a crosslinking-agent concentration of 5 mol %. The results of this study suggest that the developed procedure offers promise for the synthesis of cationic nanogels as vectors for delivery of genetic material into living cells.
  PubDate: 2012-09-01
The potential of scanning microcalorimetry for studying thermotropic conformational transitions in biomacromolecules1
- Abstract: Abstract General operational principles of a scanning microcalorimeter, methods and approaches to obtaining thermodynamic and kinetic information on the studied transition, and the existence of correlations between the structural features of a macromolecule and the measured thermodynamic parameters of denaturation transitions are considered. The results of studying the domain organization for a number of proteins and transfer poly(ribonucleic acids), the kinetics of heat denaturation, and the nature of the transitional (activated) state of macromolecules are surveyed. The potential of high-pressure scanning microcalorimetry for measuring volume changes during conformational transitions of proteins and lipids is discussed.
  PubDate: 2012-09-01
DNA compaction by nonbinding macromolecules
- Abstract: Abstract Compaction of DNA by nonbinding macromolecules such as uncharged flexible polymer chains and negatively charged globular proteins is thought to have various applications in biophysics, for example in the formation of a nucleoid structure in bacteria. A simple experimental model that has been very well studied is the classic DNA ψ-condensation induced by polymers and salt. In recent years, compaction of DNA by nonbinding macromolecules has been reconsidered under conditions that are closer to the biophysical applications, in various respect. This work is reviewed here. Topics that are considered are: DNA compaction by nonbinding globular proteins, the influence of DNA binding proteins and DNA topology on ψ-condensation, and finally, the impact of confinement on DNA ψ-condensation.
  PubDate: 2012-09-01
Behavior of hyperbranched polymers in solutions
- Abstract: Abstract Hyperbranched polycarbosilanes are investigated by the methods of molecular hydrodynamics and optics. Dependences of the hydrodynamic and conformational properties of these polymers on their molecular mass, the length of linear chains between branching points, and the chemical structure of end groups are analyzed. The hydrodynamic behavior of hyperbranched polycarbosilanes is explained by the fact that the dimensions of their macromolecules are compact and their shape is close to spherical. The convolution of chains between branching points becomes more pronounced with an increase in their length and a decrease in the molecular mass of the polymer. When end fluorinated groups are incorporated into the hyperbranched polycarbosilane, in thermodynamically good solvents and θ solvents, hydrodynamic characteristics change apparently owing to a change in the density of macromolecules in solution. In a poor solvent, the compaction of fluorinated macromolecules and a reduction in their shape asymmetry are observed. At a fixed branching degree, the hydrodynamic properties of hyperbranched polymers depend on the structural regularity of their macromolecules: In terms of hydrodynamic properties, the hyperbranched polycarbosilane with a degree of branching of 1 and a random distribution of branching points within the volume of a macro-molecule is appreciably different from a dendrimer of the same chemical nature and is close to polycarbosilanes with a degree of branching of 0.5.
  PubDate: 2011-09-01
Macromolecular nano-objects as a promising direction of polymer chemistry
- Abstract: Abstract The main features of the manifestation of polymer characteristics of macromolecular nanoobjects are summarized and analyzed in comparison with classical linear systems. This study is primarily focused on dendrimers that exhibit qualitative changes in their characteristics after passing from lower to higher generations within the same homologous series. The above changes are shown to be typical for other representatives of a similar class of polymers.
  PubDate: 2011-09-01
Polymers based on unsaturated alkoxides of refractory metals
- Abstract: Abstract Metallopolymers based on unsaturated alkoxides of refractory metals (Ti(IV), V(V), Ta(V), Nb(V)) are synthesized and characterized; their thermal behavior is studied via TGA, TMA, and DSC. It is shown that nanocomposite materials can be synthesized through the polymerization of metal-containing monomers and subsequent controlled thermolysis of the products.
  PubDate: 2011-09-01
Formation of metal-polymer hybrid nanostructures during radiation-induced reduction of metal ions in poly(acrylic acid)-poly(ethylenimine) complexes
- Abstract: Abstract The formation of nanoparticles during the radiation-induced chemical reduction of silver ions, copper ions, and nickel ions in films based on poly(acrylic acid)-poly(ethylenimine) complexes are studied via electron microscopy. This approach allows preparation of composites containing nanoparticles that are randomly distributed in the polymer matrix and materials with a regular spatial distribution of nanoparticles across the film thickness and in subsurface layers. The structure of metal-polymer hybrid materials is dependent on the irradiation conditions, the type of reduced metal ions, and their initial content in polymer matrices. The ratio between the rate of nucleation and the rate of growth of nanoparticles in the matrices of interpolyelectrolyte complexes depends on the intensity of the absorbed dose and on the mechanisms of reduction of metal ions and formation of clusters. The IR spectroscopic studies reveal the effect of nanoparticles on the chemical structure of the polymer matrix.
  PubDate: 2011-09-01
Effect of anionic-lipid-molecule geometry on the structure and properties of liposome-polycation complexes
- Abstract: Abstract The influence of anionic amphiphilic compounds that have different geometric shapes and become incorporated into bilayers on the polycation-mixed liposome interaction and the structure and properties of the resulting complexes is analyzed. Phosphatidylserine, cardiolipin, and sodium dodecyl phosphate are used as anionic lipids, and poly(N-ethyl-4-vinylpyridinium bromide) and polylysine are used as polycations. Polycation adsorption on the surfaces of all examined types of liposomes is accompanied by the neutralization of their charge, an increase in the size of particles of the systems, and quenching of fluorescence labels. Liposomes whose membranes contain incorporated cylindrical phosphatidylserine molecules retain their integrity during contact with polycations. The resulting complexes quantitatively dissociate into initial components during an increase in the salt concentration in the surrounding solution. In the case of liposomes with asymmetric anionic lipids, that is, cardiolipin and sodium dodecyl phosphate, the conditions of retaining the membrane integrity and reversible complexation are fulfilled only at relatively low molar fractions of both lipids. The obtained data witness the decisive effect of the geometry of anionic lipid molecules on the stability of complexes formed from mixed liposomes and polycations.
  PubDate: 2011-09-01
The Fifth All-Russian Conference Polymers 2010
- PubDate: 2011-09-01
Basic guidelines for the selection of polyelectrolytes that can effectively prevent thermal aggregation of enzymes without any substantial loss in their catalytic activity1
- Abstract: Abstract Factors governing thermal aggregation and thermal denaturation of a model homotetrametric enzyme, glyceraldehyde-3-phosphate dehydrogenase, electrostatically bound to a polyelectrolyte are revealed. Polyanions with sulfate or sulfonate groups in chains are the most efficient suppressors of aggregation. However, their presence promotes thermal denaturation. Short chains of relatively hydrophobic polyanions exert a strong denaturing effect that changes the secondary, tertiary, and quaternary structures of a protein. Basic guidelines for the selection of a polyelectrolyte are outlined. According to the proposed guidelines, hydrophilic high-molecular-mass macromolecules able to form stable soluble polyelectrolyte complexes with the enzyme are the most efficient at preventing thermal aggregation without substantial loss in catalytic activity.
  PubDate: 2011-09-01
Metal-complex compounds as components of initiating systems for the controlled radical polymerization of vinyl monomers
- Abstract: Abstract The effect of initiating systems based on substituted and unsubstituted metallocenes; polynuclear macrocyclic semi- and clathrochelates of Fe(II); and metal complexes of Ti(IV), Zr(IV), Fe(III), and Co(III) porphyrins on the free-radical polymerization of MMA and styrene is analyzed. Experimental data are systematized, general relationships are ascertained, and specific features of the process related to the structure of metal-complex compounds and the nature of initiators and monomers are revealed.
  PubDate: 2011-09-01