Formation of two-dimensional crystals of icosahedral RNA viruses

The formation of 2D arrays of three small icosahedral RNA viruses with known 3D structures (tomato bushy stunt virus, turnip yellow mosaic virus and bromegrass mosaic virus) has been investigated to determine the role of each component of a negative staining solution containing ammonium molybdate and polyethylene glycol. Virion association was monitored by dynamic light scattering (DLS) and virus array formation was visualised by conventional transmission electron microscopy and cryo-electron microscopy after negative staining. The structural properties of viral arrays prepared in vitro were compared to those of microcrystals found in the leaves of infected plants. A novel form of macroscopic 3D crystals of turnip yellow mosaic virus has been grown in the negative staining solution. On the basis of the experimental results, the hypothesis is advanced that microscopic arrays might be planar crystallisation nuclei. The formation of 2D crystals and the enhancing effect of polyethylene glycol on the self-organisation of virions at the air/water interface are discussed. SYNOPSIS: The formation of 2D arrays of icosahedral viruses was investigated by spectroscopic and transmission electron microscopic methods.     

聚乙二醇/二氧化钛一维光子晶体的制备及其性质研究

采用旋涂法制备了多层聚乙二醇/二氧化钛(PEG/TiO₂)一维光子晶体膜,通过控制旋涂时间、旋涂速度和聚乙二醇溶液质量浓度,制备出具有不同光子禁带的PEG/TiO₂一维光子晶体膜。制备的PEG/TiO₂膜对有机溶剂二甲亚砜(DMSO)和强碱溶液有双重响应。     

Packing nanomechanics of viral genomes

We investigate the osmotic equilibrium between a bulk polyethylene glycol (PEG) solution and DNA tightly packed in a spherical capsid. We base our analysis on the equations of thermodynamic equilibrium in terms of osmotic pressure. The equality between external osmotic pressure of PEG and osmotic pressure of tightly packed DNA gives us the DNA encapsidation curves. In this way we directly connect the wealth of existing osmotic pressure data for DNA in the bulk with the DNA encapsidation curves within small viral capsids. Specific calculations are made for a monovalent salt, Na(+) -DNA and a divalent salt, Mn(2+) -DNA that have quite different DNA encapsidation behaviors. The main conclusion of our work is that bending energy of DNA is of minor importance regarding the encapsidated DNA length, but has a non-negligible influence on the density distribution of DNA within the capsid.     

Experimental study on correlation between sound velocity and solute molecular weight in polyethylene glycol solution

In this study,ultrasound grating was used to measure the sound velocity in solutions of ethylene glycol and polyethylene glycol with molecular weights of 200,600,2000,and 10000.We found Parthasarathy empirical rule,that is,sound velocity is higher in the solution of larger molecules,is invalid in the case of polyethylene glycol solution. We tried to provide a tentative explanation using the Flory-Krigbaum's chained block cloud model.     

Optimization of salt concentration in PEG-based crystallization solutions

Although polyethylene glycol (PEG) is the most widely used precipitant in protein crystallization, the concentration of co-existing salt in the solution has not been well discussed. To determine the optimum salt concentration range, several kinds of protein were crystallized in a 30% PEG 4000 solution at various NaCl concentrations with various pH levels. It was found that, if crystallization occurred, the lowest effective salt concentration depended on the pH of the protein solution and the pI of the protein molecule; that is, higher salt concentrations were required for crystal growth if the difference between pH and pI was increasing. The linear relationship between the charge density of the protein and the ionic strength of the crystallization solution was further verified. These results suggested that the lowest effective concentration of salt in a crystallization solution can be predicted before performing a crystallization experiment. Our results can be a tip for tuning crystallization conditions by the vapor-diffusion method.     

Accurate quantification of hydration number for polyethylene glycol molecules

Hydration water can even decide the physicochemical properties of hydrated organic molecules. However, by far the most important hydration number for organic molecules, in particular polyethylene glycol which we are concerned with here, usually suffers from a large discrepancy. Here, we provide a scheme for accurate and unambiguous quantification of the hydration number based on the universal water-content dependence of glass transition temperature for aqueous solutions, testified by experimental results for polyethylene glycol molecules of a molar weight ranging from 200 to 20000.Moreover, we also clarify the fundamental misunderstanding lying in the definition and quantification of hydration water for PEG molecules in the literature, therein the hydration number for PEG in water-rich solutions has been determined at a critical concentration, across which the properties of the solution display obviously distinct water-content dependence.     

Optical characteristics of cadmium sulfide nanoparticles synthesized in polyethylene matrix and <Emphasis Type="Italic">ortho</Emphasis>-xylene solution

The properties of CdS nanoparticles synthesized in a polyethylene matrix and an ortho-xylene solution are compared. It is shown that these nanoparticles have different shapes, structures, and degrees of imperfection. Due to these differences, unaggregated nanoparticles in solution exhibit luminescence in contrast to nanoparticles in polyethylene. The stabilization of nanoparticles in polyethylene most probably occurs via OH groups, while nanoparticles in solution are stabilized due to partial interaction with dissolved sulfur. The absorption and luminescence spectra of samples with polyethylene are strongly distorted by reabsorption and scattering, while this effect in solution is absent due to a small concentration of nanoparticles.     

The re-entrant cholesteric phase of DNA

The character of packing of double-stranded DNA molecules in particles of liquid-crystal dispersions formed as a result of the phase exclusion of DNA molecules from aqueous salt polyethylene glycol solutions has been estimated by comparing the circular dichroism (CD) spectra of these dispersions recorded at different osmotic pressures and temperatures. It is shown that the first cycle of heating of dispersion particles with hexagonally packed double-stranded DNA molecules leads to the occurrence of abnormal optical activity of these particles, which manifests itself in the form of a strong negative CD band, characteristic of DNA cholesterics. Moreover, subsequent cooling is accompanied by a further increase in the abnormal optical activity, which indicates the existence of the “hexagonal → cholesteric packing” phase transition, controlled by both the osmotic pressure of the solution and its temperature. The result obtained can be described in terms of “quasi-nematic” layers composed of orientationally ordered DNA molecules in the structure of dispersion particles. There are two possible ways of packing for these layers, which determine their hexagonal or cholesteric spatial structure. The second heating → cooling cycle confirms these results and is indicative of possible differences in the packing of double-stranded DNA molecules in the hexagonal phase, which depend on the osmotic pressure of the solution.     

Ring pattern solutions of a free boundary problem in diblock copolymer morphology

The cross section of a diblock copolymer in the cylindrical phase is made up of a large number of microdomains of small discs with high concentration of the minority monomers. Often several ring like microdomains appear among the discs. We show that a ring like structure may exist as a stable solution of a free boundary problem derived from the Ohta-Kawasaki theory of diblock copolymers. The existence of such a stable, single ring structure explains why rings exist for a long period of time before they eventually disappear or become discs in a diblock copolymer. A variant of Lyapunov-Schmidt reduction process is carried out that rigorously reduces the free boundary problem to a finite-dimensional problem. The finite-dimensional problem is solved numerically. A stability criterion on the parameters determines whether the ring solution is stable.     

Simulation of diffusio-phoretic motion of colloidal particle suppressed by bound solutes within adsorption shell

Colloidal particle submerged in a non-equilibrium fluid with a concentration gradient of solutes experiences diffusio-phoresis. Such directional transport originates from the driving forces that exert on the fluid in a microscopic boundary layer surrounding the colloid. Based on a simple model of spherical colloid fixed in a concentration gradient of solutes, molecular dynamics simulations are performed to determine the interaction parameters that maximise the diffusio-phoretic mobility, which cannot be properly measured by conventional continuum theory. The diffusio-phoretic mobility is found to depend non-monotonically on the strength of the interaction between the colloid and solutes, due to the presence of bound solutes within adsorption shell that cannot contribute to diffusio-phoresis. The results also show that the phoretic mobility depends sensitively on the density of solutes in bulk, due to the uneven distribution of excess particles surrounding the colloid at a microscopic level. The simulations suggest that diffusio-phoresis may in principle be applied to the selective transport, separation and purification for colloidal systems. By substituting the spherical colloid with other realistic macromolecules, the model could provide results that are quantitatively comparable with experiments.     

Compatibility Studies of Polysaccharide-Based Natural and Synthetic Polymers in Aqueous Solution

Compatibility of polysaccharide-based natural polymers, xanthan gum (Xn), tragacanth gum (Traga) and acacia gum (Ac), with synthetic polymer, polyvinyl pyrrolidone (PVP) and polyethylene glycol (PEG) in aqueous solution has been investigated using the related acoustical parameters at room temperature, 303 K. The concentration of synthetic polymers PVP and PEG was varied to understand the nature of solute–solvent interaction in the polysaccharide-based natural/synthetic polymer in aqueous solution. FT-IR studies were also carried out for vibration assignment and confirmation of compatibility.     

Synthesis and characterization of MoO<Subscript>3</Subscript> nanostructures by solution combustion method employing morphology and size control

Molybdenum oxide nanostructures were synthesized utilizing the solution combustion method where the ammonium molybdate powder and an organic additive were used as precursors. Different organic additives including ethylene diamine tetra-acetic acid (EDTA), polyethylene glycol 200 (PEG 200), sorbitol and urea were used as surfactants in order to investigate the effect of additive structure on morphology and particle size of products. Also various reaction parameters such as the additive/Mo molar ratio, concentration of metal ion in solution, pH of the reaction, and temperature of the synthesis media were changed to study effects on product morphology and size. Outcomes were characterized by Scanning Electron Microscopy (SEM), X-ray diffraction, and Transmission Electron Microscopy (TEM) techniques. Results show a variety of MoO₃ nanoparticles and nanorods produced within the size range of 10–80 nm. Furthermore, microrods and microsheets were also obtained through this method whose length varied in the order of microns.     

A Novel Class of Coherent Localized Structures for the Maccari System

By means of the Backlund transformation, a quite general variable separation solution of the (2 1)-dimensional Maccari systems is derived. In addition to some types of the usual localized excitations such as dromion,lumps, ring soliton and oscillated dromion, breathers solution, fractal-dromion, fractal-lump and chaotic soliton structurescan be easily constructed by selecting the arbitrary functions appropriately, a new novel class of coherent localizedstructures like peakon solution and compacton solution of this new system are found by selecting aperopriate functions.     

Visualization of Magnetization Transfer Effect in Polyethylene Glycol Impregnated Waterlogged Wood

To visualize the condition of impregnation of polyethylene glycol (PEG) in waterlogged wood, we demonstrated magnetic transfer (MT) magnetic resonance imaging (MRI) through a series of process of PEG impregnation. Three different samples were examined; reference wood, 10 cm cut wood, and 5 cm cut wood. During this study, the upper section sample was kept immersed in water, for the middle and lower sections the concentration of PEG solution was changed at 20 wt% intervals from 20 to 100 wt%. The impregnated periods of each PEG solution concentration were 14 days. Then, MR imaging were performed with/without MT pulse. The MTR value for both 10 cm- and 5 cm-samples were shown to decrease at 20 wt% PEG at peak concentration. When the sample volume was large, e.g., 10 cm-sample, the MTR value decreased to 100 wt% PEG concentration. In contrast, when a sample volume was small, e.g., 5 cm-sample, MTR value decreased to 60 wt% PEG concentration. In conclusion, MTR analysis makes it possible to nondestructively visualize and evaluate the inner condition concerning the PEG impregnation method for waterlogged wood.     

铽配合物荧光及在农用光波长转换塑料薄膜中的应用

选择荧光效应强的稀土元素铽,以磺基水杨酸作为第一配体,以聚乙烯醇、聚乙二醇2000等为协配体,对乙醇溶液和水溶液两个体系中形成的配合物荧光进行了研究。试验确定了铽、磺基水杨酸以及聚乙烯醇、聚乙二醇2000为优良协配体的最佳用量。进一步研究发现,表面活性剂的加入对不同配合物的荧光均会产生增强效果,十二烷基磺酸钠效果最好;同时探索了酸度对体系荧光强度的影响。对于获得的铽-磺基水杨酸-聚乙烯醇配合物,其荧光激发波长为342 nm,而荧光发射波长为545 nm,将该配合物以适当比例掺加到农用塑料薄膜中,制备出可以使太阳光的紫外部分转换为作物光合作用需要的绿光的稀土光转换膜。     

黏性流体中超细长弹性杆的动力学不稳定性

基于坐标基矢摄动的方法研究了黏性流体中超细长弹性杆动力学稳定性判据与失稳后的模态选择,推导出了黏性介质中超细长弹性杆Kirchoff动力学方程的一阶摄动表示,即线性的二阶偏微分方程组.以平面扭转DNA环为例,说明了以上结果的应用,得到了平面扭转DNA环的稳定性判据及其稳定的临界区域,讨论了其失稳后的模态选择及黏性阻力对其的影响.     

Role of silica nanoparticles in conductivity enhancement of nanocomposite solid polymer electrolytes: (PEGx NaBr): ySiO2

Nanocomposite solid polymer electrolytes (NCSPEs) with conducting species other than Li ions are being investigated for solid-state battery applications. Pristine solid polymer electrolytes (SPEs) do not show ionic conductivity suitable for batteries. Addition of inert fillers to SPEs is known to enhance the ionic conductivity. In this paper, we present the role of silica nanoparticles in enhancing the ionic conductivity in NCSPEs with sodium as conducting species. Sodium bromide is complexed with the host polyethylene glycol polymer by solution cast method and silica nanoparticles (SiO₂, average particle size 7 nm) are incorporated into the complex in small amounts. The composites are characterized by powder XRD and IR spectroscopy. Conductivity measurements are undertaken as a function of concentration of salt and also as a function of temperature using impedance spectroscopy. Addition of silica nanoparticles shows an enhancement in conductivity by 1–2 orders of magnitude. The results are discussed in terms of interaction of nanoparticles with the nonconducting anions.     

Effects of organic modifiers on the size-controlled synthesis of hydroxyapatite nanorods

Size-controlled synthesis of hydroxyapatite nanorods were carried out by chemical precipitation method using polyethylene glycol (MW 600), Tween 20, trisodium citrate, and d-sorbitol as organic modifiers and starting from calcium nitrate, phosphoric acid, and ammonia solution. The influence of the organic modifiers on the sizes of the resultant HAP nanorods was investigated under different synthesis temperatures. It was found that polyethylene glycol was beneficial to the formation of HAP nanorods with a larger aspect ratio (average length/average diameter) at high synthesis temperature, Tween 20 and trisodium citrate favored the formation of small-sized HAP nanorods, and d-sorbitol helped the formation of HAP nanorods with long length at low synthesis temperatures.     

Fluorescence Dynamics of DNA Condensed by the Molecular Crowding Agent Poly(Ethylene Glycol)

Condensation of extended DNA into compact structures is encountered in a variety of situations, both natural and artificial. While condensation of DNA has been routinely carried out by the use of multivalent cations, cationic lipids, detergents, and polyvalent cationic polymers, the use of molecular crowding agents in condensing DNA is rather striking. In this work, we have studied the dynamics of plasmid DNA condensed in the presence of a molecular crowding agent, polyethylene glycol (PEG). Steady-state and time-resolved fluorescence of the recently established condensation-indicating DNA binder, YOYO-1 [G. Krishnamoorthy, G. Duportail, and Y. Mely (2002), Biochemistry 41, 15277–15287] was used in inferring the dynamic aspects of DNA condensates. It is shown that DNA condensed by PEG is more flexible and less compact when compared to DNA condensed by binding agents such as polyethyleneimine. The relevance of such differences in dynamics toward functional aspects of condensed DNA is discussed.     

A Novel Class of Coherent Localized Structures for the Maccari System

By means of the Baecklund transformation, a quite general variable separation solution of the (2 1)-dimensional Maccari systems is derived. In addition to some types of the usual localized excitations such as dromion, lumps, ring soliton and oscillated dromion, breathers solution, fractal-dromion, fractal-lump and chaotic soliton structures can be easily constructed by selecting the arbitrary functions appropriately, a new novel class of coherent localized structures like peakon solution and compacton solution of this new system are found by selecting apfropriate functions.