木质素磺酸钠在浓溶液中聚集行为的研究

利用流变和电导等实验手段研究了木质素磺酸钠(SL)在浓溶液中的聚集行为,讨论了无机盐(Na Cl、Na2SO4)、尿素及直链醇(甲醇、乙醇、正丙醇)对SL聚集行为的影响.结果表明,无机盐会促使较大SL聚集体的形成,而尿素可破坏聚集体的形成;少量直链醇加入将不利于SL聚集体的形成,但是过量醇的加入又会有利于SL聚集体的形成.从静电、氢键和疏水作用等不同角度对SL在浓溶液中的聚集行为进行了合理解释.     

拉曼光谱研究镍离子对鸡蛋清溶菌酶淀粉样纤维化动力学影响的浓度效应（英文）

本文采用拉曼光谱研究了Ni(Ⅱ)离子在高温和酸性条件下对鸡蛋清溶菌酶淀粉样纤维化动力学的影响.利用蛋白质三级和二级结构的拉曼光谱指针,检测分析了Ni(Ⅱ)离子对蛋白质三级结构展开和二级结构转化影响的浓度效应.结果证实了金属离子在动力学的加速作用.值得注意的是,通过对酰胺Ⅰ谱带的光谱分析并结合ThT荧光分析都表明,Ni(Ⅱ)离子对于形成有组织β-片层结构的淀粉样纤维有抑制作用,而在组装成其他无序结构的聚集体时,则会表现出显著的促进作用.本文为金属介导的蛋白质纤维化过程研究提供了参考信息.     

酚化合物对胰岛素淀粉样纤维化的抑制作用

采用牛胰岛素作为模型多肽分子, 对几种结构相近的简单多酚的抗多肽淀粉样纤维化作用进行了研究. 结果表明, 邻苯二酚和对苯二酚对胰岛素纤维化具有抑制作用, 并通过形成醌中间体对多肽链进行修饰, 与对苯醌作用类似; 而苯酚和间二苯酚在相同条件下, 既不能修饰多肽也无抑制纤维化作用. 在无氧条件下, 邻苯二酚和对苯二酚对胰岛素纤维化的抑制作用明显降低, 说明酚化合物经氧化形成的醌中间体是其抗胰岛素纤维化的主要活性结构.     

溶液中金属盐对溶菌酶高级结构的影响

探索蛋白质结构稳定性及其淀粉样纤维化的环境条件具有重要意义.本文采用了荧光光谱法研究溶液中的金属盐对鸡卵清溶菌酶内源荧光和淀粉样纤维化的影响.结果表明,金属盐能够增加溶菌酶的热稳定性,减小淬灭剂对内源荧光的作用,对溶菌酶的高级结构具有一定的稳定作用.另一方面,在长时间热胁迫的情况下,金属盐可促进溶菌酶分子的聚集而纤维化.金属盐的这种双重作用分别与其阳离子和阴离子的性质有关.     

1,4-二巯基苏糖醇对溶菌酶淀粉样纤维化的抑制作用

蛋白质淀粉样纤维化是很多人类疾病的重要特征,筛选蛋白质淀粉样纤维化的抑制剂对于研究和开发相关疾病的治疗药物具有重要意义。本文采用溶菌酶作为模型,探索巯基化合物1,4-二巯基苏糖醇(DTT)对蛋白质淀粉样纤维化的抑制作用。结果表明,DTT对溶菌酶淀粉样纤维化具有较强的抑制作用,其IC50数值为17μmol.L-1。DTT抑制溶菌酶纤维化的作用与其巯基结构有关。在溶菌酶分子高级结构改变产生聚集和纤维化的过程中,DTT分子的巯基通过与溶菌酶的二硫键作用改变了多肽的构象,从而改变了溶菌酶纤维化的进程。     

无机离子对Ag_3PO_4可见光降解亚甲基蓝的影响

以亚甲基蓝(MB)为模拟废水污染物,Ag3PO4为光催化剂,固定污染物初始浓度、催化剂用量、光照强度和照射时间等,探讨不同浓度的无机阴、阳离子(NO-3、Cl-、SO2-4、Na+、Ca2+、Mg2+、Al 3+)对Ag3PO4光催化降解偶氮染料MB的影响.结果表明,Na+和NO-3对Ag3PO4光催化降解MB没有明显的影响;Cl-在一定程度上对MB的降解具有促进作用;SO2-4、Ca2+、Mg2+、Al3+在不同程度上抑制了该光催化反应的进行,且抑制顺序为SO2-4Ca2+Mg2+Al 3+.     

表没食子儿茶素(EGC)对溶菌酶淀粉样纤维化的抑制作用

天然多酚化合物是蛋白质淀粉样纤维化相关疾病的潜在治疗药物。本文采用溶菌酶和表没食子儿茶素(EGC)研究了多酚化合物对蛋白质淀粉样纤维的作用。结果表明,EGC能够抑制溶菌酶的淀粉样纤维化,并能够破坏成熟的纤维结构,使纤维的淀粉样特性降低。巯基化合物二巯基苏糖醇(DTT)能够部分抑制EGC破坏纤维的作用,表明EGC可能通过与巯基结合而对多肽链进行共价修饰,从而改变了淀粉样纤维的自组装结构。根据上述结果,我们认为,多酚化合物形成醌类中间体并对多肽链的自由巯基进行修饰,是其抑制蛋白质淀粉样纤维化的主要途径。     

磷脂和硫酸肝素对αs1-酪蛋白淀粉样纤维沉淀形成的影响

利用ThT荧光分析法、透射电子显微镜和圆二色光谱检测αs1-酪蛋白形成淀粉样纤维沉淀(Fibril)的动力学过程,优化了其形成条件,研究了Fibril形成的影响因素.实验结果表明,αs1-酪蛋白在65℃高温下,pH=5～5.4的范围内,加热144 h以上,可以形成Fibril.在此过程中,αs1-酪蛋白的二级结构由α螺旋构象向β折叠构象转变.甘油磷酸胆碱D6PC可以显著地促进αs1-酪蛋白Fibril的形成,并呈浓度依赖性,说明一定条件下蛋白质可能与细胞膜的磷脂之间存在相互作用,从而导致酪蛋白二级构象的转变.硫酸肝素对αs1-酪蛋白形成Fibril无影响,说明硫酸肝素对蛋白质二级构象的影响作用因蛋白质的不同而不同,与不同蛋白质的Fibril形成机制相关.     

水/有机两相体系 1-癸烯氢氨甲基化反应中 TPPTS 和TPPDS 的协同效应

 在 RhCl(CO)(TPPTS)2-TPPTS[P(m-C6H4SO3Na)3]/TPPDS[C6H5P(m-C6H4 SO3Na)2]-CTAB (十六烷基三甲基溴化铵) 水-有机两相催化体系中, 系统考察了 TPPTS/TPPDS 摩尔比、反应压力、阳离子表面活性剂结构及其浓度对 1-癸烯氢氨甲基化反应区域选择性的影响. 结果表明, TPPDS 的加入对生成胺的区域选择性的影响非常大. 当 TPPTS/TPPDS 摩尔比为 4 时, 直链胺和支链胺之比由不加 TPPDS 时的 8.2 增加到 21.0. 可见, TPPTS 和 TPPDS 存在着明显的协同效应. 阳离子表面活性剂的结构对生成胺的区域选择性影响也很大, 加入双长链阳离子表面活性剂时区域选择性远低于单长链阳离子表面活性剂, 且形成的聚集体越紧密, 越有利于提高产物正/异比.     

小热休克蛋白Mj HSP16.5对多肽纤维生长的抑制及对成熟纤维的解聚作用

包括老年痴呆症在内的许多疾病与蛋白质或多肽的淀粉样聚集(纤维化)有关. 由于这类疾病的机制尚不清楚, 因此还没有有效的预防和治疗手段. 研究各种因素如小热休克蛋白对蛋白质或多肽淀粉样聚集的影响对开发防治相关疾病的药物具有重要意义. 甲状腺素运载蛋白(TTR)及其突变体很容易形成淀粉样纤维, 并与多种疾病相关. Mj HSP16.5是一种来源于嗜热古细菌ethanococcus jannaschii的小热休克蛋白, 它在酸性条件下具有非常高的分子伴侣活性. 本文研究了Mj HSP16.5对WTTR肽(在N端添加了色氨酸的TTR 105-115片段, 序列为WYTIAALLSPYS)纤维化的影响, 发现Mj HSP16.5能够显著地抑制WTTR肽纤维的生长, 且在Mj HSP16.5存在下, WTTR肽形成的纤维比正常条件下形成的要显著细小. 尤其是Mj HSP16.5还可以使已经成熟的WTTR肽纤维解离. 结果表明, Mj HSP16.5抑制多肽纤维的机理可能在于其能够与多肽纤维及纤维种子结合.     

Effects of lipid confinement on insulin stability and amyloid formation

We report on a study of insulin incorporation into cubic phases of mono-olein (MO), using synchrotron small-angle X-ray scattering and FT-IR spectroscopy. We studied the thermal stability and aggregation scenario of insulin as a function of protein concentration in the narrow water channels of the cubic lipid matrix and compared it with data for insulin unfolding and fibrillation in bulk water solutions. The concomitant effect of insulin entrapment on the structure and phase behavior of the lipid matrix itself was also examined. We show that the protein's unfolding behavior and stability are influenced by confinement due to geometrical limitations, and vice versa, the topological properties of the lipid matrix change as well. The addition of insulin already at concentrations as low as 0.1 wt % significantly alters the phase behavior of MO. Surprisingly, new cubic structures are induced by insulin incorporation into the lipid matrix. When insulin begins to partially unfold at higher temperatures, the structure of the new cubic phase changes and finally disappears around 60 degrees C, where the aggregation process sets in. The aggregation in cubo proceeds much faster and leads to the formation of medium-sized oligomers or clusters, while the formation of large fibrillar agglomerates, as observed for bulk insulin aggregation, is largely prohibited. Hence, the results yield valuable information about the use of cubic mesoporous lipid systems as a medium for long-term storage of insulin and aggregation-prone proteins in general. Furthermore, the results provide new insights into the effects of soft-matter confinement on protein aggregation and fibrillation, a situation usually met in natural cell environments.     

Energetics of lysozyme adsorption on mesostructured cellular foam silica: effect of salt concentration

The heat of lysozyme adsorption on mesostructured cellular foam (MCF) silica was measured using flow microcalorimetry (FMC) to investigate the influence of a neutral salt, sodium sulfate. At concentrations up to 0.5 M sodium sulfate, a complex initial exotherm was followed by an endotherm. Protein surface coverage, the magnitudes of the exothermic heat signals and the magnitudes of the net heat of adsorption increased with sodium sulfate concentration. These observations suggest that electrostatic interactions are the principal driving force at low ionic strengths; van der Waals interactions become dominant at higher salt concentrations. Each exotherm could be deconvoluted into two exotherms, indicating multiple modes of lysozyme attachment to the silica surface. The endothermic peak, associated with protein desorption, disappeared at the highest sodium sulfate concentration (1.0 M), indicating irreversible adsorption of the protein on the MCF silica surface. The data are consistent with an adsorption mechanism in which the initial attachment of lysozyme to the surface is followed by a reorientation and formation of a secondary or stronger attachment to the surface.     

Modeling of the salt effects on hydrophobic adsorption equilibrium of protein

A two-state protein model is proposed to describe the salt effects on protein adsorption equilibrium on hydrophobic media. This model assumes that protein molecules exist in two equilibrium states in a salt solution, that is, hydrated and dehydrated states, and only the dehydrated-state protein can bind to hydrophobic ligands. In terms of the two-state protein hypothesis and the steric mass-action theory, protein adsorption equilibrium on hydrophobic media is formulated by a five-parameter equation. The model is demonstrated with the adsorption of bovine serum albumin to Phenyl Sepharose gels as a model system. The effects of salt type (sodium chloride, sodium sulfate and ammonium sulfate) on the model parameters are discussed. Then, the model formulism is simplified in terms of the small magnitude of the protein dehydration equilibrium constant in the model. This simplification has returned the model derived on the basis of the two-state protein hypothesis to its original mechanism of salt effects on the hydrophobic adsorption of protein. This simplified model also creates satisfactory prediction of protein adsorption isotherms.     

Effects of ammonium sulfate and sodium chloride concentration on PEG/protein liquid-liquid phase separation

When added to protein solutions, poly(ethylene glycol) (PEG) creates an effective attraction between protein molecules due to depletion forces. This effect has been widely used to crystallize proteins, and PEG is among the most successful crystallization agents in current use. However, PEG is almost always used in combination with a salt at either low or relatively high concentrations. Here the effects of sodium chloride and ammonium sulfate concentration on PEG 8000/ovalbumin liquid-liquid (L-L) phase separation are investigated. At low salt the L-L phase separation occurs at decreasing protein concentration with increasing salt concentration, presumably due to repulsive electrostatic interactions between proteins. At high salt concentration, the behavior depends on the nature of the salt. Sodium chloride has little effect on the L-L phase separation, but ammonium sulfate decreases the protein concentration at which the L-L phase separation occurs. This trend is attributed to the effects of critical fluctuations on depletion forces. The implications of these results for designing solution conditions optimal for protein crystallization are discussed.     

Influence of sodium sulfate or sodium sulfite on the solubilization of benzylalcohol in cationic micellar solutions

The enthalpy of benzylalcohol (BzOH) solution has been determined as a function of alcohol concentration in aqueous trimethyltetradecylammonium bromide (TTAB) solutions in the presence of sodium sulfite or sodium sulfate up to high salt concentration. The electrolytes studied do not seem to induce TTAB sphere-torod transition at least up to 0.6 mol/kg of salt. Comparison with the enthalpic behavior of BzOH in sodium dodecylsulfate solutions and with that of 1-pentanol in both cationic and anionic micellar solutions suggests that the solubilization of BzOH in TTAB solutions is specifically favored by intramolecular interactions between alcohol molecules within the cationic micelles. The replacement of the bromide counterions by the sulfite or sulfate ions has been studied using potentiometry with an ionselective electrode in the case of trimethylhexadecylammonium bromide (CTAB). No difference could be detected between the effects of either divalent anions on the rate of change of the bromide ion-condensation with the salt/surfactant concentration ratioR. The degree of counter-ion condensation on micellar surface depends not only on theR values, but also on the total surfactant concentration.     

Supersaturation control in aragonite synthesis using sparingly soluble calcium sulfate as reactants

Sparingly soluble calcium salts were studied as reactants in the synthesis of needle-like precipitated calcium carbonate (PCC). The morphology and aspect ratio of the PCC particles were characterized with SEM. Polymorphs and crystal size were characterized using X-ray diffraction. The counterions of the sparingly soluble salts influenced the growth kinetics of PCC as well as the polymorphism and morphology of product particles. Either chrysanthemum-like or needle-like aragonite can be synthesized from calcium sulfate and sodium carbonate depending on the supersaturation and synthesis conditions. Low concentration and slow addition rate of sodium carbonate solution were favorable to the formation of aragonite. Addition of sodium sulfate to the reaction system (calcium chloride and sodium carbonate) promoted the formation of aragonite and decreased the crystal size of aragonite due to the decrease of supersaturation and adsorption of sulfate ion. Too much added sodium sulfate, however, did not further increase the aragonite fraction. An optimal temperature for the formation of aragonite was found to be ca. 60 degrees C. Slow dissolution kinetics of sparingly dissoluble salt also is very important for controlling PCC polymorphism and morphology.     

表面活性剂胶束化物理化学性质研究

通过电导法考查温度和盐浓度对十二烷基硫酸钠(SDS)临界胶束浓度(CMC)的影响,研究表面活性剂形成胶束过程的物理化学性质。根据拟相分离模型求得胶束化热力学函数,并讨论体系电导活化能随温度和SDS浓度变化关系。结果表明:SDS的CMC随温度升高而增加,随氯化钠浓度增大而减小。在热力学上SDS在水溶液中形成胶束是一个自发、放热、熵增的过程;在动力学上,SDS溶液电导率与温度关系符合Arrhenius公式,通过电导活化能信息可揭示离子型表面活性剂形成胶束的机理特征。     

Monitoring and inhibition of insulin fibrillation by a small organic fluorogen with aggregation-induced emission characteristics

Amyloid fibrillation of proteins is associated with a great variety of pathologic conditions. Development of new molecules that can monitor amyloidosis kinetics and inhibit fibril formation is of great diagnostic and therapeutic value. In this work, we have developed a biocompatible molecule that functions as an ex situ monitor and an in situ inhibitor for protein fibrillation, using insulin as a model protein. 1,2-Bis[4-(3-sulfonatopropoxyl)phenyl]-1,2-diphenylethene salt (BSPOTPE) is nonemissive when it is dissolved with native insulin in an incubation buffer but starts to fluoresce when it is mixed with preformed insulin fibril, enabling ex situ monitoring of amyloidogenesis kinetics and high-contrast fluorescence imaging of protein fibrils. Premixing BSPOTPE with insulin, on the other hand, inhibits the nucleation process and impedes the protofibril formation. Increasing the dose of BSPOTPE boosts its inhibitory potency. Theoretical modeling using molecular dynamics simulations and docking reveals that BSPOTPE is prone to binding to partially unfolded insulin through hydrophobic interaction of the phenyl rings of BSPOTPE with the exposed hydrophobic residues of insulin. Such binding is assumed to have stabilized the partially unfolded insulin and obstructed the formation of the critical oligomeric species in the protein fibrillogenesis process.     

Interfacial tension of ethylene and aqueous solution of sodium dodecyl sulfate (SDS) in or near hydrate formation region

The interfacial tensions between ethylene and an aqueous solution of SDS were measured using the pendant-drop method at 274.2 and 278.2 K and in the pressure range from 0.1 to 3.1 MPa, including hydrate formation points. The concentrations of sodium dodecyl sulfate (SDS) aqueous solution were 0, 100, 300, 500, 600, 700, 800, 900, and 1000 ppm. The effects of pressure on the critical micelle concentration (CMC) and the surface excess concentration were studied. It was demonstrated that both the CMC and the saturated surface excess concentration decreased with the increase of pressure.