锌离子与牛血清白蛋白相互作用的研究

用荧光光谱法研究了锌离子(Zn2+)与牛血清白蛋白(BSA)的作用机制.实验表明,Zn2+对BSA具有荧光猝灭作用,其猝灭方式为静态猝灭.求出了猝灭常数、结合常数及结合位点数.利用同步荧光光谱研究了Zn2+对BSA分子荧光光谱的影响.     

烟碱与牛血清白蛋白相互作用的光谱研究

在0.1 mol·L-1的磷酸氢二钠-柠檬酸体系中,采用荧光光谱、紫外吸收光谱研究了牛血清白蛋白(BSA)与烟碱的相互作用。荧光滴定表明这种相互作用使BSA的内源荧光猝灭,尼古丁和BSA形成1∶1稳定复合物。不同温度和酸度下的猝灭作用证实其静态猝灭行为和疏水作用机制。紫外吸收光谱和同步荧光光谱表明,相互作用引起BSA构象变化,而同步荧光光谱提示结合位点更接近于色氨酸。     

柠檬酸钠与牛血清白蛋白相互作用的荧光光谱研究

利用荧光光谱技术研究了柠檬酸钠和牛血清白蛋白(BSA)之间的相互作用。柠檬酸钠对BSA荧光的猝灭机制属于形成复合物的静态猝灭过程。在20.0、32.0℃和36.5℃下柠檬酸钠与BSA之间的结合常数Ka分别为2.51×104、1.07×104、9.1×103L.mol-1,结合位点数近似为1。二者结合反应的主要作用力类型为氢键或范德华力。当pH值为7.4时二者的结合作用最强,同步荧光光谱显示两者的结合位点更接近于色氨酸。同时也研究了金属离子对二者作用的影响。     

同步荧光光谱法结合分子对接研究金雀花碱与牛血清白蛋白间相互作用

金雀花碱(Cy)是一种生物碱,主要存在于豆科毒豆属植物种子中。Cy具有较强的生物活性,特别是作为戒烟药物已得到广泛应用。在模拟生理条件下,应用荧光光谱法研究了Cy同牛血清白蛋白(BSA)之间的相互作用以及Cy猝灭BSA荧光发射的机理。详细考查了水浴温度、水浴时间以及溶液pH等因素对荧光猝灭的影响,并且通过Stem-Volmer方程计算了Cy与BSA间的结合类型、结合位点数目以及结合常数。结果表明,Cy与BSA可形成摩尔比为1∶1的非共价复合物,其结合常数为5.6×103,其猝灭类型为静态猝灭。同步荧光光谱研究结果表明,Cy的结合主要影响BSA 的Trp残基的荧光发射。进一步应用分子对接研究表明,氢键与疏水作用是Cy与BSA形成复合物的主要推动力。Cy与BSA中Trp213及其周围的氨基酸残基间存在氢键与疏水作用,这种作用将改变Trp213所处微环境的疏水情况,从而导致BSA的荧光发生猝灭。     

防己诺林碱与牛血清白蛋白相互作用的研究

在不同温度下,用荧光猝灭光谱、同步荧光光谱和紫外-可见吸收光谱,研究了防己诺林碱与BSA相互作用的光谱学行为。防己诺林碱对BSA有较强的荧光猝灭作用。根据不同温度下防己诺林碱对BSA的荧光猝灭作用,利用Stern-Volmer方程处理实验数据,表明防己诺林碱对BSA的荧光猝灭作用属于静态猝灭。根据Frster非辐射能量转移理论计算出了防己诺林碱与BSA间的结合距离R(27 ℃ 2.51 nm; 37 ℃ 2.72 nm; 47℃ 2.89 nm)、结合常数K_A(27 ℃ 1.05×105 L·mol-1; 37 ℃ 3.31×105 L·mol-1; 47 ℃ 7.24×105 L·mol-1)及对应温度下的热力学参数。热力学数据表明二者主要靠疏水作用力结合,同时用同步荧光光谱探讨了防己诺林碱对BSA构象的影响。     

荧光光谱法研究虎杖苷与牛血清白蛋白的相互作用

在不同温度下,采用荧光光谱,紫外-可见吸收光谱研究了虎杖苷与牛血清白蛋白(BSA)的相互作用。虎杖苷对BSA的荧光有较强的猝灭作用。根据292K和311K时虎杖苷对BSA的荧光猝灭作用,利用Stern-Volmer方程及双倒数方程处理实验数据,表明虎杖苷对BSA的荧光猝灭作用属于动态猝灭过程,根据Foerster非辐射能量转移理论计算出了虎杖苷与BSA间的结合距离r=3.61nm,结合常数(Kb)分别为5.189×105L·mol-1(292K),1.382×105L·mol-1(311K)及对应温度下的热力学参数。实验结果表明二者主要靠疏水作用力结合,采用同步荧光光谱探讨了虎杖苷对BSA构象的影响。     

头孢噻肟钠与牛血清白蛋白的相互作用

采用荧光光谱、同步荧光光谱、紫外光谱研究了水溶液中头孢噻肟钠(CTX)与牛血清白蛋白(BSA)之间的相互作用.结果表明:CTX能显著猝灭BSA的内源荧光并以静态猝灭为主;两者以摩尔比1∶1结合,结合常数分别为1.20×104(298K)、7.63×103(308K)和6.69×103(313K)L·mol-1;根据热力学参数判断CTX与BSA之间的作用力主要为氢键和范德华力;依据Foester非辐射能量转移理论计算出CTX与BSA之间的结合距离r为3.26nm,同步荧光光谱研究表明CTX能够使BSA构象发生变化.     

胡椒碱与牛血清白蛋白的相互作用

采用荧光光谱技术研究了胡椒碱与牛血清白蛋白（BSA）的相互作用。根据测定不同温度下胡椒碱对BSA的猝灭常数,证实了荧光猝灭过程为静态猝灭,由热力学参数焓变（ΔH）小于零和熵变（ΔS）大于零,推断出胡椒碱与BSA之间主要靠静电引力相结合,生成自由能变（ΔG）为负值,表明胡椒碱与BSA的作用过程是一个自发过程;并应用同步荧光光谱技术考察了胡椒碱对BSA构象的影响。     

光谱法研究壳寡糖铕配合物与牛血清白蛋白的相互作用

采用紫外光谱、荧光光谱研究壳寡糖-Eu配合物与牛血清白蛋白(BSA)相互作用,探讨其作为抗肿瘤药物的可能。紫外光谱显示:加入壳寡糖-Eu后,BSA的紫外吸收增强且吸收峰发生蓝移,表明壳寡糖-Eu配合物与BSA形成了复合物;荧光猝灭光谱显示壳寡糖-Eu对BSA荧光有猝灭作用,猝灭机理主要为静态猝灭,并存在非辐射能量转移。计算了室温下壳寡糖-Eu与BSA的结合常数和结合位点数分别为1.20×105L·mol-1和1.29。     

几种EGCG金属配合物与牛血清白蛋白的相互作用

运用荧光光谱法研究了几种EGCG金属配合物(EGCG-M)与牛血清白蛋白(BSA)的相互作用。实验结果表明,几种EGCG-M对BSA的荧光光谱有明显猝灭作用,两者之间的相互作用为静态猝灭,并得到了静态猝灭常数、结合常数及结合位点数等数据。     

牛血清白蛋白对Pluronic聚合物胶团形成的影响研究

用吡啶作为荧光探针研究了嵌段共聚物PluronicF108胶团形成以及牛血清白蛋白(BSA)对嵌段共聚物胶团形成的影响。研究表明,BSA阻碍嵌段共聚物的胶团形成,BSA与嵌段共聚物疏水链段的疏水相互作用是其阻碍嵌段共聚物胶团形成的主要原因。     

Electrochemical switching of fluorescence from europium ions dissolved in poly(ethylene oxide) oligomers

Europium salts were dissolved in poly(ethylene oxide) (PEO) oligomers. The europium ions were revealed to be electrochemically redox-active in PEO oligomers. Trivalent europium ions (Eu³⁺) showed red fluorescence (λ_em = 614 nm) in PEO oligomers, and a new intensive blue fluorescence (λ_em = 450 nm) was obtained after reducing the Eu³⁺ into Eu²⁺ by giving negative potential (−0.7 V versus Ag). Reversible fluorescence switching was also carried out by changing the given potential alternately. Sufficient color change required about 20 min because of slow electrode reaction. The fluorescence intensity from europium ions was affected by the molecular weight of matrix PEO. The amount of terminal hydroxyl groups and local viscosity were revealed to affect the fluorescence as the vibrational quenching and diffusion coefficient, respectively. The PEO oligomer with average molecular weight of 600 gave the most intensive fluorescence.     

A simple swelling and anchoring method for preparing dense and stable poly(ethylene oxide) layers on polystyrene surfaces

In order to obtain dense and stable poly(ethylene oxide) (PEO) layers for reducing protein adsorption, polystyrene (PS) plates were first soaked in chloroform/methanol mixed organic solvent to swell the polymer. The swelled PS plates were then immersed into Pluronic F127 (amphiphilic block copolymer) aqueous solution, Pluronic F127 molecules were adsorbed favorably on the swelled PS surfaces. After evaporation of organic solvent, the adsorbed Pluronic F127 molecules were trapped and anchored permanently on the PS substrates. The dense and stable PEO layers anchored on the PS surfaces can effectively inhibit protein adsorption.     

Stimuli-responsive poly(ethylene oxide)-b-poly(2-vinylpyridine)-b-poly(ethylene oxide) triblock copolymers and complexation with poly(acrylic acid) at low pH

The self-organization of the double hydrophilic triblock copolymer poly(ethylene oxide)-b-poly(2-vinylpyridine)-b-poly(ethylene oxide), PEO-b-P2VP-b-PEO, was investigated in dilute aqueous solution under several experimental conditions using turbidimetry, as well as static and dynamic light scattering. As a result of the temperature-sensitive properties of the end PEO blocks and the p H-responsive properties of the middle P2VP block, the formation of large star-like micellar nanostructures is observed at high p H, while at low p H, but in the presence of salt and at high temperature, flower-like micelles are formed. Moreover, the viscosimetric and dynamic light scattering studies at low p H revealed that micelle-like nanostructures are formed upon mixing the triblock copolymer with poly(acrylic acid), PAA, due to hydrogen bonding interpolymer complexation.     

Single-molecule single crystals of poly(ethylene oxide)

Single-molecule single crystals were prepared from two fractions of poly(ethylene oxide) (PEO) with narrow molar mass distribution and an equimolar mixture of the two fractions. It was proven that the molar mass distribution of the single-molecule single crystals from the mixed sample corresponds to an addition of those of the pure fractions. Well-shaped crystals were obtained after isothermal crystallization or on annealing. A variety of morphologies typical for multimolecule single crystals of PEO were found and are described on the basis of the various known modes of twinning. The results are in agreement with the known unit cell of PEO.     

Conductance study of poly(ethylene oxide)- and poly(propylene oxide)-based polyelectrolytes

The ionic conductivity of poly(ethylene oxide) and poly(propylene oxide) in pure solution form, individually complexed with salts of Na⁺ and Li⁺, with and without plasticizer (propylene carbonate) and in blended form with individual salt with and without plasticizer, was studied. The conductance measurements were made at various concentrations of salt polymer complexes and at different temperatures. The effects of temperature and plasticizer concentration were measured from Arrhenius conductance plots. It is shown that the addition of salts in pure PEO increases conductance many times. The plasticizer has also same effect. The blending of PEO with PPO gives enhanced conductivity as compared to pure PEO. The activation energies were determined for all the systems which gave higher values for pure PEO and the value decreases with the addition of Li and Na salts and further decreases with the addition of plasticizer. The blending has also lowered the activation energy values which mean that incorporation of PPO in PEO has decreased crystallinity and the amorphous region has increased the local mobility of polymer chains resulting in lower activation energies.     

On the Intramolecular Excimer Formation of 1,10-Bis(1-Pyrene)Decane in Organized Media

The formation of an intramolecular excimer of 1,10-bis(1-pyrene)decane in sodium dodecyl sulfate (SDS)/bovine serum albumin (BSA) and SDS/poly(ethylene oxide) (PEO) solutions was studied by steady-state and time-resolved fluorescence methods to determine the effect of viscosity. The viscosity-dependent ratio between intramolecular excimer and monomer fluorescence intensities of 1,10-bis(1-pyrene)decane was obtained by steady-state fluorescence measurements. The results show that in micelle-like clusters formed in SDS/BSA and SDS/PEO systems, the microviscosity is higher than in free micelles. It was found that Birks' kinetic model was not valid in this case, and the monomer and excimer fluorescence decays had to be fitted by a sum of three exponentials. The excimer formation kinetics in constrained systems is more complex than in homogeneous solutions, but it is possible to find an empirical parameter depending on viscosity.     

Electrochemical characteristics of the dimercaptan-poly(ethylene oxide) grafted polyaniline electrodes

The electrochemical and transport properties of the 2,5-dimercapto-1,3,4-thiadiazole (DMcT)/poly(ethylene oxide) (PEO) grafted polyaniline electrodes and the DMcT/polyaniline electrode interfaced with the poly(acrylonitrile) (PAN) based solid-polymer-electrolyte (SPE) containing lithium perchlorate and ethylene carbonate were studied. Compared with the electrochemical and transport properties of the DMcT/polyaniline electrode, the capacitance and voltammetric current density, obtained by cyclic voltammetry, were increased for the electrode with low grafted polyaniline (less than 3 mol. %), while decreased when the applied copolymers were highly grafted ones. The charge transfer resistance obtained from impedance measurements was much smaller in the DMcT/PEO grafted polyaniline electrode than that in the DMcT/polyaniline electrode, and more pronounced reduction of charge transfer resistance was observed for the electrode with low grafted polyaniline. The diffusion coefficient of lithium cation in the electrode was increased when the PEO grafted polyaniline was used as an electrode material, however, the increase of the diffusion coefficient was less significant at higher graft degrees. All these changes in electrochemical and transport characteristics by the employment of PEO chains upon polyaniline backbones were attributed to the enhancement of lithium ion solvation and enlarged free volume in the electrode.     

Structure and crystallization of molecular complexes between poly(ethylene oxide) and hydroxybenzenes

The phase diagrams of the binary systems poly(ethylene oxide) (PEO)-resorcinol and poly(ethylene oxide)-p-nitrophenol show the presence of molecular complexes with well-defined stoichiometries. The crystal structure of these two molecular complexes has been determined from wide-angle x-ray diffraction patterns of stretched films and spherulites. The morphology of the two complexes crystallized from the melt is investigated by differential scanning calorimetry and small-angle x-ray scattering. The crystallization of the PEO-resorcinol complex from the melt gives integral-folded crystals with either extended chains (EC) or n-folded chains (n-FC). As observed for PEO oligomers, the fraction of EC crystals of the PEO-resorcinol complex increases with the crystallization temperature to give finally only EC crystals but in a larger range of crystallization temperatures than for pure PEO. On the other hand, the PEO-p-nitrophenol complex crystallizes over all the studied crystallization range as stable nonintegral-folded (NIF) crystals. Two proposals related to the crystal structure of these complexes and their mode of growth are invoked to explain these two greatly different morphologies at the lamellar level.     

Optical characterization of poly (ethylene oxide)/zinc oxide thin films

The optical characterization of poly (ethylene oxide)/zinc oxide thin films has been done by analyzing the absorption spectra in the spectral wavelength region 380–800 nm using a ultraviolet-spectrophotometer at room temperature. Thin film polymer composites made of poly (ethylene oxide) (PEO) containing zinc oxide (ZnO) filler concentrations (0%, 2%, 6%, 10%, and 14%) by weight were used in this study. The optical results obtained were analyzed in terms of the absorption formula for non-crystalline materials. The optical energy gap and other basic optical constants such as dielectric constants and optical conductivity were investigated and showed a clear dependence on the ZnO filler concentration. It was found that the optical energy gap for the composite films is less than that for the neat PEO, and that it decreases as the ZnO concentration increases. Enhancement of the optical conductivity was observed with increase in the ZnO concentration. Dispersion of refractive index was analyzed using the Wemple–DiDomenico single oscillator model. The refractive index (n), extinction coefficient (k), and dispersion parameters (E_o, E_d) were calculated for the investigated films.