Synthesis,static, and dynamic light scattering studies of soluble aromatic polyamide

Aromatic polyamide was synthesized via condensation polymerization of 4‐aminophenyl sulfone (APS) with isophthaloyl chloride (IPC) using N,N‐dimethyl acetamide (DMAc) as a solvent under anhydrous conditions. The purified aramid was studied by laser light scattering (LLS) in dimethyl sulfoxide (DMSO), a thermodynamically good solvent at 20°C. Static and dynamic light scattering studies permitted to determine the weight average molecular weight , radius of gyration , second virial coefficient A₂, the hydrodynamic radius R_H, and the diffusion coefficient D. Light scattering experiments were conducted at five concentrations ranging from 0.27 to 2.5 g/L. LLS measurement is also a very useful technique to study the aggregation or association in a polymer system as long as the large “clusters” are reasonably stable in time. The intensity autocorrelation function obtained on the quasi‐elastically scattered light showed a simple diffusive relaxation mode. The ratio of radius of gyration to the hydrodynamic radius, i.e. ～ 1.3 indicates that the polyamide chain has coil conformation in DMSO at 20°C. Copyright © 2008 John Wiley & Sons, Ltd.     

Aggregation behavior and interaction of an amphiphilic drug imipramine hydrochloride with cationic surfactant cetyltrimethylammonium bromide: light scattering studies

The aggregation behavior and interaction of an amphiphilic antidepressant drug imipramine (IMP) hydrochloride with the cationic surfactant cetyltrimethylammonium bromide (CTAB) have been studied using light scattering (both static and dynamic) techniques. Due to rigid tricyclic hydrophobic moiety present in the molecule, the drug shows interesting association behavior. The static light scattering measurements show that the self-association of IMP commenced above a well-defined critical micellar concentration (CMC), which decreases with increasing the mole fraction of the CTAB surfactant. Both the excess Gibbs energy (ΔG(ex)) and the Gibbs energy of micellization (ΔG(M)°) are negative, and decrease with increasing mole fraction of the surfactant. The hydrodynamic diameters (d(h)) of the micellar aggregates were also evaluated using the dynamic light scattering measurements. The data indicate formation of larger aggregates by IMP and CTAB due to mixed micellization and subsequent micellar growth. The results have been analyzed using different models (viz., Clint, Motomura, Rosen, Rubingh, etc.) for mixed micelle formation.     

Structure formation of surfactants in concentrated sulphuric acid: a light scattering study

A common cationic surfactant,n-hexadecylammonium hydrogensulphate, dissolved in concentrated sulphuric acid, has been studied by static and dynamic light scattering. Micelle formation has been observed even in this unusual solvent. An apparent molar mass of 45 500±4.5% was found for the aggregates. A translational diffusion coefficientD ₀=5.5×10^–9 cm²/s was measured which gave a hydrodynamically effective radius ofR _h=17.7 nm. The geometric radius of gyration wasR _g=76.2 nm. The ratioR _g/R _h=4.33 is indicative for rodlike structures. Assuming a polydispersity ofL _w/L _n=2 this corresponds to a cylinder ofL _w=152 nm. An axial ratiop _w=(L _w/d)=60.4 nm was estimated which leads to a cylinder diameter of 2.53 nm. At surfactant concentrations higher than 5% (w/vol) the rod-like micelles aggregate to form more globular structures. The time correlation function, recorded by dynamic light scattering, exhibited a two-step decay which indicates a bimodal distribution of particle sizes. The fast motion coincides with that of the micelles at low concentrations while the other is slower than the fast one by three orders of magnitude and corresponds to the translational motion of large clusters.     

维多利亚蓝B瑞利光散射技术测定阿魏酸

基于阿魏酸与维多利亚蓝B在中性介质中形成离子缔合物,导致瑞利光散射增强,建立了一种测定阿魏酸的分析方法。研究了离子缔合物反应的适宜条件,结果表明:在优化的条件下,阿魏酸浓度在5.60×10-7~1.34×10-5mol/L范围内与瑞利散射光的增强呈良好的线性关系,方法的检出限为3.26×10-7mol/L。已用于实际样品中阿魏酸的测定。     

Electrokinetic properties of mixed solutions of dodecyldimethylamine oxide and sodium dodecyl sulfate: specific adsorption effects of small ions

Electrophoretic light-scattering measurements and potentiometric titrations were carried out on aqueous mixtures of dodecyldimethylamine oxide and sodium dodecyl sulfate. The electrophoretic mobility and the surface charge density of the micelles were always negative, ranging from –2.5 to –3.1×10^–4 cm²V^–1s^–1, and –0.033 to –0.045 cm^–2, respectively, for all surfactant mixing ratios, indicating the specific adsorption of Cl^–, in addition to Na⁺, on micelles. The solution pH, as well as the aggregation number previously reported, displayed maxima at intermediate surfactant mole fractions, that is, the non-ideal behavior. The fractional adsorption of Na⁺ per surfactant molecule in the micelles increased gradually with mixing fraction up to 0.82 atX=[SDS]/([SDS]+[C₁₂DAO])=1, while that of Cl^– decreased from 0.25 atX=0 to zero atX>0.4.     

A resonance light scattering ratiometry applied for binding study of organic small molecules with biopolymer

Resonance light scattering (RLS) technique is a creative application of light scattering signals detected by using a common spectrofluorometer, but it has drawbacks such as the fluctuation of signals caused by poorly quantified or variable factors. Herein we develop a RLS ratiometry to overcome the drawbacks of the technique and apply to measure the binding nature of organic small molecules (OSM) with biopolymer using the binding of cation porphyrins with heparin (HP) as an example. In near neutral solution, cationic porphyrins meso-tetrakis [(trimethylammoniumyl) phenyl] porphyrin (TAPP) and meso-tetra (4-methylpyridy) porphyrin (TMPyP-4) interact with heparin, resulting in hypochromatic effect, and enhanced RLS signals. Linear relationship could be established between the ratio of enhanced RLS signals at two wavelengths, where the maximum and minimum are available in the ratio curve of UV-vis spectrum of porphyrin to that of heparin-porphyrin complex, and the logarithm of heparin concentration, and thus a wide dynamic range detection method of biopolymers could be developed. In comparison with RLS method, this RLS ratiometric one is less affected by environmental conditions such as pH, ionic strength. The mechanism of these interactions was investigated based on the charge density distribution of the two porphyrin molecules and it could be concluded that the enhanced RLS intensity is proportionally promoted by the charge capacity of components in the complex. Additionally, the binding number and binding constant were measured scientifically by Scatchard plot.     

Characterization of sodium dodecylsulphate and dodecylphosphocholine mixed micelles through NMR and dynamic light scattering

The complexity of biological membranes leads to the use of extremely simplified models in biophysical investigations of membrane‐bound proteins and peptides. Liposomes are probably the most widely used membrane models due, especially, to their versatility in terms of electric charge and size. However, liquid‐state NMR suffers the lack of such a model, because even the smallest liposomes slowly tumble in solution, resulting in a dramatic signals broadening. Micelles are typically used as good substitutes, with sodium dodecylsulphate (SDS) and dodecylphosphocholine (DPC) being the most widely employed surfactants. However, they are always used separately to mimic prokaryotic and eukaryotic membranes, respectively, and accurate investigations as a function of surface charge cannot be performed. In this work, the critical micelle concentration (CMC) of binary mixtures with different SDS/DPC ratios has been determined by following the chemical shift variation of selected ¹H and ³¹P NMR signals as a function of total surfactant concentration. The regular solution theory and the Motomura's formalism have been applied to characterize the micellization both in water and in phosphate buffer saline, and results were compared with those obtained directly from the experimental NMR chemical shift. The ζ‐potential and size distribution of the mixed micelles have been estimated with dynamic light scattering measurements. Results showed that SDS and DPC are synergic and can be used together to prepare mixed micelles with different negative/zwitterionic surfactants molar ratio. Copyright © 2013 John Wiley & Sons, Ltd.     

结晶紫探针瑞利光散射技术测定安乃近

在弱碱性条件下,结晶紫与安乃近相互作用后,导致瑞利光散射增强,建立了一种简便、快速、灵敏及选择性好的测定安乃近的分析方法。在390 nm处的ΔIRLS最大,增强的瑞利散射光与0.06~0.40 mg·L-1范围的安乃近呈良好的线性关系,方法的检出限(3Sb/S)为0.017mg·L-1。该法用于市售安乃近药物中安乃近含量的测定,结果满意。     

花菁-脱氧核糖核酸的共振光散射光谱及其分析应用

研究了一种苯并噻唑阳离子花菁与脱氧核糖核酸(DNA)作用的共振光散射光谱,在pH 6.0的六次甲基四胺-HCl缓冲介质中,痕量DNA的加入使花菁在590nm的共振光散射强度显著增强.在最佳实验条件下,增强的共振光散射强度与DNA浓度具有良好的线性关系,据此建立了一种测定DNA的共振光散射光谱法.方法的线性范围为:小牛胸腺DNA(CT DNA),0～20μg/mL,鱼精子DNA(FS DNA),0～ 15μg/mL;检出限分别为0.005 μg/mL和0.008μg/mL.该方法已用于合成样品中DNA的测定.     

Determination of proteins in human serum by combination of flow injection sampling with resonance light scattering technique

A flow injection method combined with Resonance light scattering detection was developed for the determination of protein concentration in human serum samples. This method is based on the enhanced RLS signals of protein binding with the dye acid chrome blue K. The enhanced RLS intensities at 264 nm, in an acidic aqueous solution, were proportional to the protein concentration over the range of 2.0–40.0 μg·mL⁻¹ for human serum albumin (HSA) and the limit of detection (3σ) is 85 ng·mL⁻¹. This method was successfully applied to the quantification of total proteins in human serum samples. The maximum relative standard deviation is less than 2% and the recovery is between 97 and 103% for the standard addition method. The sample throughput was 60 h⁻¹.     

Study on the interaction among molecules and the determination of DNA by light scattering with a new type rhodanine derivative

In this paper the resonance Rayleigh scattering (RRS) and second-order scattering (SOS) spectrums of interaction between deoxyribonucleic acid (DNA) and 3-(4′-methylphenyl)-5-(2′-sulfophenylazo) rhodanine (4MRASP) in the environment of surface active substance sodium dodecyl sulfate (SDS) were reported. The light scattering intensity of 4MRASP was enhanced obviously and directly proportional to the concentrations of DNA when DNA was present. Based on this, two new determination methods of DNA were established with high sensitivity and selectivity, and the limits of detection were 8.00 and 1.07 ng mL⁻¹. They were applied to the determination of trace amounts of nucleic acid in synthetic and practical samples with satisfactory results. At last, the active mechanism among molecules was studied by ultraviolet spectrum, scattering spectrum and thermodynamics, which showed that the active force was changed from hydrophobic force to electrostatic force before and after SDS was added, and the mechanism of sensitization effect of SDS was proposed.     

Characterization of polymer materials by scattering techniques,with applications to block copolymers

The application of six techniques—static and dynamic light scattering, small-angle neutron and X-ray scattering, neutron and X-ray reflectivity—to the characterization of polymer materials is summarized. Emphasis is placed on the similarities and differences among the various techniques, and on recent advances in experimental practice. Twelve examples from the recent literature are described, most of which concern block copolymers. A brief introduction to block copolymer properties is also provided.     

Determination of proteins with Alizarin Red S by Rayleigh light scattering technique

A new protein determination method by enhanced Rayleigh light scattering (RLS) technique has been developed. In acid condition (pH=3.60), RLS of 1,2-dihydroxyanthraquinone-3-sulfonate (Alizarin Red S) can be greatly enhanced by addition of proteins, resulting in two characteristic peaks, 360 and 505 nm, respectively. The new protein assay is based on the RLS enhancement and spectrum change. The optimum condition for the reaction was investigated. The linear range is 0.20-24.9 μg ml⁻¹ for BSA and 0.20-15.5 μg ml⁻¹ for HSA. The detection limits (S/N=3) are 9.59 ng ml⁻¹ for BSA and 9.51 ng ml⁻¹ for HSA. The results of determination for human serum samples were comparable to those obtained by Bradford method. The binding stoichiometry was determined.     

光散射法研究丙烯酸十八酯和苯乙烯微乳液共聚机理

在十六烷基溴化吡啶/叔丁醇/15%丙烯酸十八酯和苯乙烯/水体系的O/W微乳液中,使用动态光散射法,研究其中两种单体共聚反应的成核机理。结果表明,聚合过程中乳胶粒成核位置主要在增溶胶囊的单体微珠中,乳胶粒主要依靠单体微珠不断提供单体而长大。     

溴甲酚绿-Triton X-100与扑草净作用的共振光散射光谱研究

研究了扑草净-溴甲酚绿-Triton X-100体系的共振光散射光谱。加入经HCl酸化的扑草净后溴甲酚绿的共振光散射光谱有明显增强,表面活性剂TritonX-100的加入使光谱强度显著增加,产生最大散射波长为562 nm的共振散射光信号,且散射光强度与扑草净的质量浓度呈线性关系,线性范围为0.01~0.35μg/mL,检出限为7.8 ng/mL。该方法已用于实际样品中扑草净的测定。     

Oil-continuous microemulsions mixed with an amphiphilic graft copolymer or with the parent homopolymer Polymer–droplet interactions as revealed by phase behavior and light scattering

Polymer–droplet interactions have been studied in AOT/water/isooctane oil-continuous microemulsions mixed with an amphiphilic graft copolymer, or with the parent homopolymer (AOT = sodium bis(2-ethylhexyl) sulfosuccinate). The graft copolymer has an oil-soluble poly(dodecyl methacrylate) backbone and water-soluble poly(ethylene glycol) side chains. Pseudo-ternary polymer/droplet/isooctane phase diagrams have been established for both the parent homopolymer and the graft copolymer, and the two types of mixture display entirely different phase behavior. The homopolymer–droplet interaction is repulsive, and a segregative phase separation occurs at high droplet concentrations. By contrast, the graft copolymer–droplet interaction is attractive: the polymer is insoluble in the pure oil, but dissolves in the microemulsion. A comparatively high concentration of droplets is required to solubilize even small amounts of polymer. Static and dynamic light scattering has been performed in order to obtain information on structure and dynamics in the two types of mixture. For optically matched microemulsions, with a vanishing excess polarizability of the droplets, the polymer dominates the intensity of scattered light. The absolute intensity of scattered light increases as phase separation is approached owing to large-scale concentration fluctuations. Dynamic light scattering shows two populations of diffusion coefficients; one population originates from “free” microemulsion droplets and the other from the polymer (for homopolymer mixtures) or from polymer–droplet aggregates (for mixtures with the graft copolymer). The graft copolymer forms large polymer–droplet aggregates with a broad size distribution, which coexist with a significant fraction of free droplets.     

Separation of monosaccharides by hydrophilic interaction chromatography with evaporative light scattering detection

Hydrophilic interaction liquid chromatography (HILIC) was used to separate monosaccharides that are common in N-linked oligosaccharides in glycoproteins and other compounds. A TSKgel Amide-80 column was eluted with 82% acetonitrile, in 5 mM ammonium formate (pH 5.5). Column temperature was 60 degrees C and evaporative light scattering was used for detection (ELSD). With this method, L-fucose, D-galactose, D-mannose, N-acetyl-D-glucosamine, N-acetylneuraminic acid, and D-glucuronic acid were separated, with detection limits of 0.3-0.5 microg for each monosaccharide, and intermediate precisions were 3-6% RSD (n=6).     

共振光散射光谱研究噻嗪红R与牛血清白蛋白的作用及其分析应用

研究了噻嗪红R(Thiazine red R,TR)与牛血清蛋白(BSA)作用的共振光散射(RLS)光谱特征。考察了各种影响因素,并计算出了BSA与TR的结合比(质量之比)为1.25。结果表明,在优化条件下体系的RLS强度与蛋白质浓度在一定范围内具有良好的线性关系,据此建立了一种蛋白质测定的新方法。在最佳实验条件(TR,2.0×10-5mol/L;pH2.36)下,BSA的线性范围是0.01~5.0μg/mL,检出限为1.4ng/mL。该方法已用于合成样品及尿液的测定。     

Determination of proteins by flow injection analysis coupled with the Rayleigh light scattering technique

A novel flow injection analysis (FIA) method with Rayleigh light scattering (RLS) detection was developed for the determination of protein concentrations. This method is based on the weak intensity of RLS of p-nitrohenzene-azo-3,6 disulfo-1-amino-8-naphthol-7-azo-benzene disodium salt (Amide Black-10B) which can be enhanced by addition of protein in weakly acidic solution. It has proved that the application of this method to quantify the proteins by using human serum albumin was available in real samples. In addition, this method is very sensitive (the determination limits are 0.11 μg/mL for human serum albumen (HSA) and 0.85 μg/mL for bovine serum albumen, BSA), simple, rapid and tolerance of most interfering substances. The FIA-RLS method was more stabile than the general RLS method and the average R.S.D. value of FIA-RLS less than general RLS. The effects of different interfering substances will be also examined. The amount of proteins in human serum sample was determined and the maximum relative error was no more than 3.00% as well as the recovery was between 94.9 and 105.9%.     

基于与全氟辛烷磺酸作用共振光散射法测定盐酸小檗碱

在pH 1.81 Britton-Robinson缓冲介质中,盐酸小檗碱与全氟辛烷磺酸相互作用,在290 nm处产生显著增强的散射信号.其增强强度与盐酸小檗碱质量浓度在0.03～7.8μg/mL范围内呈线性关系,据此建立了盐酸小檗碱的共振光散射测定方法,检出限达4.4 ng/mL.方法用于药片含量测定,RSD<4.4%...