Ultrasonic Absorption in Aaneous Polyelectrolyte Solutions

Ohne Zusammenfassung     

Study on Segmental Motion and Ion Binding in Polyelectrolyte Solutions by Ultrasonic Spectroscopy

The ultrasonic absorption spectra of aqueous solutions of polyacrylate (PA), polyphosphate (PP), and polystyrenesulfonate (PSS), neutralized by tetramethylammonium hydroxide (TMAOH), were measured. The effects of addition of tetramethylammonium chloride (TMACl) and sodium chloride (NaCl) to the polyelectrolyte solutions were investigated in the frequency range from 500 kHz to 100 MHz. Two ultrasonic relaxation processes due to the local segmental motions were observed. The relaxation frequency for TMAPP solution decreased as the ionic strength was increased by the addition of TMACl. For the other two polymer solutions, the ionic strength did not affect the relaxation spectra. The addition of NaCl led to an increase of the ultrasonic absorption, which was ascribed to ion binding. The ultrasonic absorption due to the ion binding was estimated by subtracting the contribution of the segmental motion from the measuring ultrasonic spectra. The volume changes accompanying the ion binding for polyacrylate and polyphosphate salts were estimated to be 5 and 8 cm³-mol^?1, respectively.     

胶原大分子自组装研究进展

胶原是人类最主要的结构蛋白,在体内通过自组装形成具有D带的纤维结构,构成人体的各种组织。胶原蛋白具有优异的生物相容性、生物可降解性、无毒性、低免疫性等特点,在材料科学、生物医学、组织工程、生物传感器等领域得到了越来越多的研究和应用。近年来,人们发现,通过合理调控外界环境,胶原蛋白在体外能自组装形成有序的超分子聚集结构,胶原蛋白在体外的自组装行为引起了研究者的广泛关注,逐渐成为研究的热点。本文概括了胶原的自组装机理、外界环境条件对胶原自组装的影响以及胶原自组装基复合材料等方面的工作。     

Interactions of Diglycine in Aqueous Saccharide Solutions at Varying Temperatures: A Volumetric,Ultrasonic and Viscometric Study

Densities, viscosities and speeds of sound were measured for ternary mixtures of diglycine (0.05 to 0.30 mol⋅kg⁻¹) in 2, 4 and 6 mass-% aqueous xylose, L(-)arabinose, and D(-)ribose solutions at 288.15, 298.15 and 308.15 K and at atmospheric pressures, using a DSA 5000 instrument. The limiting apparent molar volume, limiting apparent molar adiabatic compressibility and their corresponding slopes were computed using the density and speed of sound data. Corresponding transfer functions have also been determined. The viscosity data have been analyzed on the basis of the Jones-Dole equation. The viscosity B-coefficient and Gibbs energy of activation of viscous flow per mole of solvent and solute have been evaluated. Hydration numbers, pairwise and triplet interaction coefficients have also been evaluated from these data. The variations of these parameters with concentration and temperature clearly suggest the roles of diglycine and saccharides in solute–solvent interactions.     

Properties of Spreaded Collagen I Monolayers on the Surface of Aqueous tert-Butanol and n-Hexanol Solutions

Properties of the monolayers of collagen isolated from the sclera of pig's eye are studied at the air–water interface with increasing tert-butanol or n-hexanol concentrations in a subphase. In the case of aqueous n-hexanol solutions, its adsorption on the subphase surface results in the formation of mixed monolayer whose properties depend on n-hexanol concentration in the subphase and the ratio between the number of alcohol and collagen molecules in the monolayer. At higher n-hexanol surface concentration, the phase separation of the monolayer into the domains of the condensed phase of alcohol and fibrous collagen occurs. A decrease in water activity in the presence of tert-butanol leads to a drastic reduction of collagen surface activity. This effect can be explained by both the constrained collagen spreading on the surface of tert-BuOH solutions and adsorption of alcohol molecules on collagen resulting in macromolecule hydrophilization. Alcohol critical concentrations are disclosed above which collagen monolayers are not formed.     

The Effect of Aqueous Salt Solutions on the Melting of Collagen and the Viscosity of Gelatin

Measurements of shrinkage temperatures (T_S) for fibrous collagen, of equilibrium degree of swelling (v^?1) for the same in the amorphous state, and of intrinsic viscosity ([η]) for randomly coiled gelatin are reported. The data were obtained for a large variety of salts which are typical representatives of lyotropic series. The order of anions and cations for decreasing T_S and increasing both v^?1 and [η] (generally, for increasing salting in) is F^? < SO^2- ₄ < acetate < Cl^? < Br^? < NO^? ₃ < I^? < SCN^? and K⁺ < Mg²⁺ < Na⁺ < Cs⁺ < Li⁺ < Ca²⁺. For salts of ions at the extreme left of the series (salting-out agents) the shrinkage temperature in solutions of different salt concentration (C_S) is controlled by the amount of diluent in equilibrium swelling with the molten network, and the shape of T_S vs. C_S curves can be represented by conventional theories valid for binary polymer diluent systems based on a lattice model with a single interaction parameter. In such cases the salt-water solution behaves as a single component diluent and its effect on the measured properties is described as a diluent effect.     

Ultrasonic Degradation of Hydroxypropyl Cellulose Solutions in Water,Ethanol, and Tetrahydrofuran

Ultrasonic degradations of hydroxypropyl cellulose (HPC) have been carried out in water, ethanol, and tetrahydrofuran (THF) solutions. In the HPC-water system, cavitation intensity did not increase linearly with ultrasound intensity because of a lower threshold of ultrasonic intensity below which cavitation does not occur. At 27°C the rate of degradation in the three solvents followed the order water > ethanol > THF which is not in line with their characteristic impedance values. The rate of degradation for 20 kHz, 70 W ultrasound intensity was found to increase with a decrease in solution volumes, concentration of HPC, and temperature. Increased rate of degradation at lower temperatures supports the concept based on sonoluminescence experiments that it is the cavitation in a polymer solution that is responsible for ultrasonic degradations and the dissolved polymer molecules do not act as cavitation nuclei. Increased surface tension and density of the solvent are thought to be responsible for improved cavitation at low temperatures. Infrared spectroscopy and x-ray analysis of HPC subjected to ultrasonic treatments remained unchanged, suggesting that there were no chemical or structural (e.g., degree of order) changes on irradiation. The decreases in molecular weights on irradiation arise due to random chain scission whereas similar decreases in Huggins coefficients can be attributed to physical changes (decrease in molecular weight or branching) in the degraded HPC samples.     

Ultrasonic Study of Basic α‐Amino Acids in Different Acetate Salt Solutions at Different Temperatures

The ultrasonic velocity (U), has been measured for three α‐amino acids, namely L‐lysine monohydrochloride, L‐arginine and L‐histidine in solutions (1 mol/L aqueous) of sodium acetate (SA), potassium acetate (PA) and calcium acetate (CA) at different temperatures (303.15, 308.15, 313.15, 318.15 and 323.15 K). With the help of these results various ultrasonic derived parameters, viz. isentropic compressibility (κ_s), change in isentropic compressibility (Δκ_s), relative change in isentropic compressibility (Δκ_r), specific acoustic impedance (Z), relative association (RA), and apparent molal compressibility (?) have been estimated. The results have been interpreted in the light of intermolecular interactions between solute and solvent.     

Raman Study of Aluminum Chloride-Dimethylsulfone Solutions

The Raman spectra of AlCl(3)-LiCl-dimethylsulfone mixtures with different molar compositions have been recorded as a solid (300 K) and as a melt (400 K). In any case, only AlCl(4)(-) ion lines at 120, 179, and 347 cm(-)(1) were observed; we were unable to detect any other chloroaluminate species. Furthermore, some bands assigned to the Al[(CH(3))(2)SO(2)](3)(3+) octahedral coordination compound are evidence for a high AlCl(3) content.     

Molecular Understanding of Collagen Stabilization: Interaction of Valeraldehyde with Collagen

The present study explains the molecular level interaction of valeraldehyde with collagen. Valeraldehyde is a monoaldehyde, which involves crosslinking with protein through covalent linkages. The role of valeraldehyde as a crosslinking agent for collagen stabilization was studied. Molecular modeling approaches was used to understand the interaction of collagen like peptide with valeraldehyde, which mimic the aldehyde tanning processes involved in protein stabilization. Crosslinking efficiency of valeraldehyde was found to increase with an increase in concentration due to the higher availability of aldehydic groups involved in crosslinking with collagen. Valeraldehyde interacted collagen membrane showed an increase in thermal stability by 25°C at pH 8. In the presence of valeraldehyde, collagen fibrils nucleation center was shifted from a lower to a higher range. Shift in the nucleation center was observed in the reduction of gelling time. Water accessibility in valeraldehyde interacted collagen membrane was reduced due to a higher crosslinking rate in the collagen. Modified collagen membrane by valeraldehyde at incubation of about 96 h showed higher resistance to collagenolytic activity of 81%. The amino groups reacting appear to be involved in crosslinking with valeraldehyde. Several interaction sites were identified and the docking energy obtained was ?5.539 kcal/mol. The participation of the aldehyde group with amino groups in collagen was observed, which plays a dominant role in the stabilization of peptide by valeraldehyde. It was found that complexes exhibit covalent bonding, hydrogen bonding and electrostatic interaction in the process of stabilization.     

超声雾化ICP－AES的研究

报道了超声雾化器改装后作为电感耦合等离子体发射光谱（ＩＣＰ－ＡＥＳ）的进样装置。研究了多元素同时分析的最佳实验条件。在高频功率为３．１×０．７６ＫＷ、载气流量０．７２Ｌ／ｍｉｎ和观察高度１．３ｃｍ的条件下，对大多数元素其谱线较强而背景辐射较弱。     

沸石与酸性水溶液反应的动力学机制

利用连续搅拌筒反应器(CSTR)对天然沸石与酸性水溶液的反应动力学进行研究, 通过改变流速、 pH值等参数, 对反应速率进行计算和比较. 同时利用二次离子质谱(SIMS)、扫描电镜(SEM)对反应后的沸石表面进行分析研究. 实验结果表明, 沸石中的Si、Al、Na的释放速率在多数情况下不相同, 沸石的溶解为不一致溶解作用. 25 ℃、1.01×10⁵ Pa条件下, 硅的释放速率为：在pH=2.45溶液中反应时, -rSi=kS(aH+)1.25/ (aSi)0.60；在pH=3.26溶液中反应时, -rSi=kS(aH+)1.50/(aSi)0.25(S为矿物材料的表面积). SIMS研究显示, 天然沸石与酸性水溶液的反应中, 在沸石表面Si、Al、Na在100 nm的厚度范围内, 随着离表面距离的改变, 在近表面范围内Na、Al大量淋失, 有H⁺浸入. 此外, SEM分析结果显示, 天然沸石与纯水及酸性水溶液反应后, 表面形貌显著不同.     

含醇溶液的热力学研究Ⅱ.醇的水溶液的超额焓

提出了一个醇与水混和的热力学模型，它由三步组成，分别考虑了醇与水的物 理混合，醇和水的自缔合破坏以及它们间的交叉缔合．据此建立了一个超额焓方程 ．检验的结果表明，它能满意地描述含醇水溶液的超额焓随组成和温度的变化规律．     

Study of Salt Effects on the Micelle-Monomer Exchange Process of Octyl-, Decyl-, and Dodecyltrimethylammonium Bromide in Aqueous Solutions by Means of Ultrasonic Relaxation Spectroscopy

Spreading of a tiny macroscopic droplet of a nonvolatile, completely wetting liquid over a flat solid is considered. A liquid in creeping is subjected to capillary forces and long-range molecular forces. The droplet may be surrounded with a precursor wetting film. This paper deals with the problem of determining of the microscopic parameter that influences the interface shape near the apparent line of wetting; this is regarded as the inverse problem in the hydrodynamics of wetting. If the system includes a precursor film, the microscopic parameter coincides with the maximum thickness of the film. A series of inverse equations for the microparameter is obtained, which relate it to, first, the current geometric parameters of the macroscopic drop part and, second, the spreading time. A method for determining how the microparameter depends on the wetting line speed is proposed. The theory expands the opportunity to perform macroscopic measurements and reveals additional parameters. The inverse relations may be used to experimentally study the growth of the maximum thickness of a precursor film during drop spreading. Copyright 2000 Academic Press.     

Collagen mimetic dendrimers

The synthesis of single-chain, scaffold (TRIS)- and dendrimer-assembled collagen mimetics (both Gly-Pro-Nleu and Gly-Nleu-Pro sequences) is reported. From the CD spectra and the thermal denaturation studies it can be readily seen that mimetics prepared from the Gly-Nleu-Pro sequence form more thermally stable triple helices than the Gly-Pro-Nleu sequence. Furthermore, the 162-residue collagen mimetic dendrimers exhibit enhanced triple helical stability compared to equivalent scaffold-terminated structures by a substantial increase in the melting temperature in H2O and 2:1 EG/H2O. The concentration dependence for the melting transition was measured which determined that the stabilization effect arises from the intramolecular clustering of the triple helical arrays about the core structure. This ensemble excludes solvent from the interior portion of the array which stabilizes the triple helical bundle.     

Magnetochemical Study of 3d-Metal Complexes in Solutions

Possibilities of studying liquids and solutions of paramagnetic substances magnetochemically were considered. The systematized experimental data on the magnetic susceptibility of separate solvents and diamagnetic and paramagnetic complexes in the solutions presented were obtained using the developed method of measurement and the procedure of calculating the magnetic characteristics of the substances. Applications of the magnetochemical method for studying complexation and the properties and structure of coordination compounds were discussed.     

A Cryo-TEM Study of Protein-Surfactant Gels and Solutions

Oppositely charged globular protein and surfactant systems, such as lysozyme-sodium dodecyl sulfate (SDS) and ovalbumin-dodecyltrimethylammonium chloride (DOTAC) form precipitate, gel, and colorless solution in water over a wide concentration range. Bluish solutions are also recognized in connection with the redissolution of precipitate as well as prior to the gel formation. For the lysozyme-SDS system the bluish solution has been suggested to consist of finely dispersed gel particles in solution. The oppositely charged bovine serum albumin (BSA)-DOTAC-water system forms only a large, clear solution phase and a narrow, bluish solution region within a very limited surfactant concentration range. In the lysozyme-SDS system the formation of protein-surfactant aggregates and their growth and breakdown are studied in detail by cryogenic-transmission electron microscopy (cryo-TEM) method. In particular a series of samples with an increased surfactant concentration at fixed 4 wt% of lysozyme is studied. Imaging of the bluish solution at different protein concentrations exhibits large aggregates in the form of rod-like, sheet-like, and star-like objects which are attributed to the gel. At excess amounts of SDS, in the colorless solution, only small objects are detected. In the ovalbumin-DOTAC-water and BSA-DOTAC-water systems large aggregates are also observed in the bluish solutions. Colorless solutions for these two systems show the presence of small objects in the cryo-TEM micrographs. Ultrathin sections of the lysozyme and ovalbumin gels fixed with OsO(4) also show the presence of aggregated structures as judged from the transmission electron microscopy observations. Copyright 2000 Academic Press.     

褐藻糖胶及其与胶原复合物的体外抗凝血活性研究

用FTIR、UV对从海带中提取的褐藻糖胶结构进行了分析。采用部分凝血活醇时间、凝血酶原时间和凝血醇时间作为评价标准，对其体外抗凝血活性作了初步的评价，并与肝素的抗凝血活性作比较。结果表明：褐藻糖胶具有类似肝素的多糖结构，具有较好的抗凝血活性，但低于肝素。将褐藻糖胶固定于胶原上，所得的胶原-褐藻糖胶复合物仍具有一定的抗凝血活性。     

Volumetric and Ultrasonic Investigation of Glycylglycine in Aqueous FeCl<Subscript>3</Subscript> Solutions

Viscosity, ultrasonic velocity and density measurements have been carried out for glycylglycine in aqueous FeCl₃ solution as a function of molality at T=288.15 K, 298.15 K and 308.15 K. The experimental data have been used to derive properties such as isentropic compressibility (κ _S ), change in isentropic compressibility (Δκ _S ), relative change in isentropic compressibility (Δκ _S /κ ₀), apparent molar compressibility, volume and their limiting apparent molar quantities along with the constants S _K , S _V and viscosity B-coefficient. The obtained thermodynamic properties have been discussed in terms of molecular interactions.     

超声辐照制备SrFeO3降解苯酚光催化性能研究

采用超声辐照柠檬酸络合法制备了复合氧化物SrFeO₃,以苯酚为光催化探针分子,以450 W高压汞灯为光源(主波长>410 nm),研究了SrFeO₃光催化性能.研究表明,经过超声辐照制备的SrFeO₃光催化活性提高一倍以上. XRD、TEM、DRS表征结果表明,超声辐照制备的SrFeO₃粒径均匀、分散性好、粒径较小,光吸收红移显著.探讨了超声提高催化性能的机理.