Hg^2＋ -牛血清白蛋白复合体系中蛋白质微观结构的研究

研究了Hg2+在生物体内与牛血清白蛋白相互作用的毒性机理以及蛋白质的微观结构变化.测定了Hg2+与牛血清白蛋白(BSA)复合体系的红外光谱(FT-IR)和圆二色谱(CD),并对图谱进行拟合解析处理.红外光谱实验数据表明Hg2+与BSA发生作用的结合位点可能包括-SH、-OH和-NH基团,采用红外拟合技术对BSA二级结构的变化进行了研究,结果表明蛋白质α-螺旋结构含量降低,β-折叠结构含量升高.圆二色谱图也表明由于一定浓度的Hg2+与BSA结合,从而导致蛋白质的二级结构被破坏,这与拟合红外光谱得到的蛋白质二级结构数据相吻合.Hg2+与牛血清蛋白作用致使蛋白质的构象改变,形成金属离子与蛋白质作用的复合物,因而蛋白质失去活性导致生物体发生病变.     

电化学石英晶体阻抗和FTIR-ATR研究牛血清白蛋白在羟基磷灰石、TiO2表面的吸附

用电化学石英晶体阻抗法(EQCI)和衰减全反射红外光谱法(FTIR-ATR)研究了牛血清白蛋白(BSA)在纳米生物活性材料TiO_2和羟基磷灰石(HAP)上的吸附行为,获得了BSA吸附过程中电极表面的质量变化和电极/蛋白质界面双电层中电容变化以及BSA构象变化等信息。以2步骤连串反应机理分析BSA吸附动力学。结果表明,BSA在2种电极表面的吸附过程均分为吸附和重排2个过程,BSA在TiO_2上吸附速度慢于在HAP上的吸附,且难达到稳定状态。根据Sauerbrey方程结合Martin方程估算了BSA在TiO_2和HAP上饱和吸附时的表面质量覆盖度,分别为1．12×10~(-6)和1．09×10~(-6)g/cm~2。红外谱图结果还表明,生物材料的表面组成对蛋白质吸附动力学和蛋白质结构变化均有影响。BSA在HAP表面吸附时的响应更大,并对蛋白质二级结构的变化影响更大。     

咪唑型离子液体与牛血清蛋白的缔合特性

通过紫外-可见光谱、荧光光谱、同步荧光光谱、圆二色谱、衰减全反射红外光谱、负染-透射电镜、等温滴定微量热等实验方法系统地探讨了咪唑型离子液体与牛血清蛋白(BSA)的缔合特性.结果发现,离子液体[Bmim]Cl的加入使得BSA的紫外吸收强度增加,同时也会导致其荧光猝灭,并且这种猝灭是静态猝灭.同步荧光的研究结果表明,[Bmim]Cl分子可与蛋白质中接近色氨酸残基的区域发生相互作用,使蛋白质的构象和内部的疏水结构发生改变;负染色法透射电镜直观地显示了加入离子液体后形成的蛋白质-离子液体复合物结构逐渐变大;圆二色谱和衰减全反射红外光谱表明:在离子液体与BSA缔合过程中,离子液体的加入使得BSA二级结构中的α-螺旋和β-折叠的含量降低,从而引起蛋白质二级结构的变化;表面张力法和等温滴定微量热法进一步证实上述缔合作用为静电作用和疏水作用共同作用的结果,但离子液体的烷基链与BSA疏水内腔之间的疏水作用是离子液体与BSA缔合的主要驱动力.     

掺镁羟基磷灰石的合成及对蛋白质吸附性能的影响

采用超声化学法合成掺杂镁纳米羟基磷灰(Mg-HAP),改变羟基磷灰石纳米粒子的表面吸附性能,研究合成条件对纳米粒子对牛血清蛋白(BSA)吸附性能的影响,通过FT-IR、XRD、TEM等测试手段表征纳米粒子的化学组成、晶相和形貌,得到具有良好的生物相容性和吸附性能的掺镁羟基磷灰石。     

纳米羟基磷灰石/胶原复合材料制备方法比较研究

低温下,通过将水热合成的纳米羟基磷灰石浆料与中性胶原溶胶共混和在中性胶原中原位形成羟基磷灰石两种方法制备羟基磷灰石／胶原复合材料,采用XRD、FTIR、扫描电镜、透射电镜和力学性能测试等方法对两种复合材料的特性进行了表征。通过对两种方法制备的复合材料的特性进行比较,发现两种方法均制备得到了纳米羟基磷灰石／胶原复合材料,复合材料在晶相组成、化学组成、纳米羟基磷灰石晶体尺寸、胶原纤维的结构等方面都与天然骨相似。但原位合成纳米羟基磷灰石晶体的结晶度比水热合成的纳米羟基磷灰石更接近于自然骨,原位合成的羟基磷灰石／胶原复合材料的均匀性、界面结合紧密度、力学性能等方面均优于共混法。原位合成法是改善纳米羟基磷灰石／胶原复合材料均匀性和力学性能的有效方法。     

聚乙烯醇与牛血清白蛋白的相互作用及对其构象的影响

在生理条件下, 使用凝胶过滤色谱、荧光光谱法、差示扫描量热分析和傅里叶变换红外光谱法(FTIR)研究了牛血清白蛋白(BSA)与聚乙烯醇(PVA)的相互作用. 实验结果表明, PVA与BSA结合形成复合物, 在其相互作用过程中, BSA色氨酸的发射荧光部分被猝灭, 但是, 相互作用并没有明显改变色氨酸的微环境; 差示扫描量热分析结果提示, BSA与PVA之间的相互作用可能破坏了PVA或BSA的分子内作用力; 用红外光谱法结合可增强分辨率的傅里叶去卷积技术和高斯曲线拟合技术共同用于对BSA与PVA复合物冻干粉中BSA酰胺Ⅰ带的定量分析, 发现冻干粉BSA分子中与分子间相互作用相关的β-折叠组分含量明显减少, 但是, 可用于衡量冻干状态蛋白质结构完整性的α-螺旋组分含量没有降低. 对冷冻干燥后样品中的可溶性BSA分析结果提示, PVA可以保护BSA冷冻干燥过程中的稳定性.     

钛基表面纳米羟基磷灰石涂层的电泳沉积

应用沉淀法合成纳米羟基磷灰石,并以电泳沉积法在粗糙化的钛表面制备纳米结构的羟基磷灰石涂层.纳米涂层有利于保持羟基磷灰石的化学组成和结构,制备的涂层均匀并且无裂缝,烧结后涂层仍保持纳米结构,其烧结温度也明显降低。钛表面经化学处理后,可形成很多微孔和TiO2薄层,增强了涂层和基体之间的结合.涂层的结合力为 18±2. 5MPa,硬度和杨式模量分别为 32. 0和 2. 4GPa.     

简单方法制备羟基磷灰石中空微球

无需添加任何有机物和金属离子, 以易得的中空球形碳酸钙(CaCO3)与磷酸氢二钠(Na2HPO4)作为反应物在常压下制备出羟基磷灰石中空微球. 通过场发射扫描电子显微镜(FESEM)、扫描电子显微镜(SEM), X射线粉末衍射(XRD)等手段对制备的羟基磷灰石中空微球的结构、组成和形貌进行了表征, 考察了不同反应温度对中空球形貌的影响. 实验结果表明, 所制备的羟基磷灰石微球是由短针状的纳米粒子组成的, 直径为2-4 μm. 对反应机理进行了初步探讨.     

阴离子氨基酸表面活性剂调控下水热合成羟基磷灰石纳米片

利用水热合成方法, 在含有氨基酸结构的阴离子表面活性剂N-酰基十二烷基肌氨酸钠(Sar-Na)的控制下, 合成具有较大长径比(aspect ratio)的片状纳米羟基磷灰石晶体. 采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)和傅立叶变换红外(FTIR)光谱表征, 并分析了合成产物的形貌、结构和组成. 结果表明, 在Sar-Na的调控下合成了长度0.5-1.0 μm、宽约30 nm的片状羟基磷灰石晶体, 其长径比约为20:1. 考察了表面活性剂Sar-Na的用量对羟基磷灰石形貌的影响. 随着Sar-Na的添加及用量的增加, 羟基磷灰石由椭圆形变为长片状, 并且片的两端逐渐变尖. 结果显示了Sar-Na对羟基磷灰石形貌的控制作用, 为合成具有较大长径比的羟基磷灰石纳米片提供了一个新的途径.     

可生物降解肝素钠/两性壳聚糖复合物用于蛋白药物pH响应释放研究

制备了一类可生物降解肝素钠两性壳聚糖复合物(HPACS),并探索将其用于蛋白药物pH响应释放.两性壳聚糖由壳聚糖与丙烯酸加成反应得到,丙烯酸取代度可通过丙烯酸壳聚糖投料比调控;用胶体与pH浊度滴定研究了肝素钠与两性壳聚糖的复合作用,发现两组分在一定pH范围内能通过静电相互作用形成复合物,复合转变临界pH(pHΦ)与两性壳聚糖中丙烯酸取代度有关,取代度越低,pHΦ值越高.以牛血清白蛋白(BSA)为模型,测定了其在复合物中包埋及不同pH介质中的释药行为.结果表明,BSA可以在非常温和条件下有效包埋于复合物中,包埋率接近100%;BSA从复合物中释放具有很高的pH响应性,释放转变在很窄的pH范围内(<0.4pH单位)完成,释放转变临界pH(pH′Φ)可由两性壳聚糖中丙烯酸取代度调控.复合物形成和蛋白质释放在对pH依赖性上存在很好的相关性.同时还发现,在中性介质中(pH7.4),复合物对BSA具有很好的缓释作用,BSA持续释放时间可达15天左右.     

生理盐水中牛血清白蛋白与碳酸钙的相互作用研究

珍珠、贝壳和甲壳是生物矿化的产物,具有高强度、高韧性。人们已对它们的组成、结构等进行了大量的研究犤１～４犦。结果表明,它们的主要成分是碳酸钙,但由于含有少量的蛋白质等有机基质,使其结构具有特殊的组装方式,从而显示出与纯碳酸钙迥然不同的优良物理性质和重要的生物功能。另一些研究表明胆结石、尿结石等异常生物矿化产物中也含有一定量的碳酸钙犤５犦。然而生物矿化过程非常复杂,其机理至今尚无统一说法。因此模拟生物矿化过程,了解有机基质在矿化过程中的作用,已成为化学、生物、医学和材料等多学科相互渗透和相互交叉的…     

Heavy metal immobilization in aqueous solution using calcium phosphate and calcium hydrogen phosphates

This study examines the possibilities for removing heavy metal cations from water with calcium phosphate, calcium hydrogen phosphate, and calcium dihydrogen phosphate at 293 K. It was reported that immobilization of aqueous heavy metal cations, which is known to be one of the characteristic properties of calcium hydroxyapatite, proceeded favorably with these phosphates. Calcium phosphate, calcium hydrogen phosphate, and calcium dihydrogen phosphate could favorably remove Pb2+ from aqueous solution. Calcium hydrogen phosphate also removed aqueous Cu2+, Co2+, and Cd2+, whereas these cations were not immobilized by calcium phosphate and calcium dihydrogen phosphate. A contribution of the dissolution-precipitation mechanism to immobilization with these phosphates is suggested.     

Spectroscopic study of conformation changes of bovine serum albumin in aqueous environment

The secondary structural changes of protein aqueous solutions with and without calcium cations were investigated by attenuated total reflection-Fourier transform infrared (ATR-FTIR) technology.     

Adsorption and bioactivity studies of albumin onto hydroxyapatite surface

Bovine serum albumin (BSA) may have an inhibitory or promoter effect on hydroxyapatite (HA) nucleation when apatite is precipitated in a medium containing the protein. In this study we evaluated the influence of BSA on the precipitation of calcium phosphate phases (CP) from simulated body fluid (SBF) when the protein was previously bounded to HA surface. The kinetics of BSA immobilization onto hydroxyapatite surface was performed in different buffers and protein concentrations in order to adjust experimental conditions in which BSA was tightly linked to HA surface for long periods in SBF solution. It was shown that for BSA concentration higher than 0.1mg/mL the adsorption to HA surface followed Langmuir-Freundlich mechanisms, which confirmed the existence of cooperative protein-protein interactions on HA surface. Fourier Transformed Infrared Attenuated Total Reflectance Microscopy (FTIRM-ATR) evidenced changes in BSA conformational state in favor of less-ordered structure. Analyses from high resolution grazing incident X-ray diffraction using synchrotron radiation (GIXRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) showed that a poorly crystalline calcium phosphate was precipitated on the surface of HA discs coated with BSA, after the immersion in SBF for 4 days. The new bioactive layer had morphological characteristics similar to the one formed on the HA surface without protein. It was identified as a carbonated apatite with preferential crystal growth along apatite 002 direction. The GIXRD results also revealed that BSA layer bound to the surface inhibited the HA dissolution leading to a reduction on the formation of new calcium phosphate phase.     

羟基磷灰石与牛血清白蛋白相互作用的原位红外光谱研究

应用原位(in situ)全反射红外光谱研究牛血清白蛋白在电化学法制备的羟基磷灰石表面的吸附和成键行为, 探索电化学法制备的HA生物材料/生物环境界面过程和生物相容性的微观本质.     

空心纳米磷酸钙载药体系的制备与表征

非离子表面活性剂Tween 80和PEG 6000在水溶液中以一定的比例混合可形成稳定的类磷脂囊泡结构,这些囊泡可以作为模板来合成磷酸钙纳米空球颗粒。所制备的磷酸钙材料的结构和形貌通过TEM,SEM,FTIR,XRD进行了表征,是尺寸为100～150 nm左右的无定形磷酸钙空心颗粒。磷酸钙具有良好的生物相容性,因此这些具有空心结构特征的磷酸钙可发展为理想的载药体系。我们以牛血清蛋白(BSA)为模型体系研究了材料的载药和释放性能,发现所获得的空心纳米磷酸钙不仅具有良好的蛋白质负载量而且还具有优异的可释放性,明显优于传统的羟基磷灰石体系。     

Preparation and characterization of new hybrid organic/inorganic systems derived from calcium (alpha-aminoalkyl)-phosphonates and -phosphonocarboxylates

We have studied the phenomenon of calcium complexation by lab synthesized amphiphilic (alpha-aminoalkyl)-phosphonocarboxylic or -phosphonic acids. The electrical conductivity of aqueous solutions of sodium salts of all these acids was measured versus the volume of a calcium salt solution added. It appeared that calcium complexes are formed in a Ca/P atomic ratio close to 1. Calcium phosphonocarboxylates and calcium phosphonates were also precipitated by mixing aqueous solutions of disodium salts of phosphorus amphiphiles and calcium nitrate solutions. Before chemical analysis, these complexes were calcined to remove the organic part. In the mineralized products, calcium and phosphate were assayed: the Ca/P atomic ratio was equal to 1. X-ray diffraction and IR spectroscopy showed that they are made entirely of beta pyrophosphate (Ca2P2O7), a result in agreement with previous chemical analysis. The chemical formula of the starting calcium complexes could be written as CaL2H2O (L=ligand). The SEM micrographs of these complexes show plate-like structures. XRD patterns are characteristic of layered structures. These facts suggest that calcium complexes are composed of alternating bimolecular layers of calcium alkylphosphonocarboxylates or calcium alkylphosphonates, the chains being tilted and partially interdigitated.     

Spectroscopic investigation of interaction between mangiferin and bovine serum albumin

The mechanism of interaction between mangiferin (MA) and bovine serum albumin (BSA) in aqueous solution was investigated by fluorescence spectra, synchronous fluorescence spectra, absorbance spectra and Fourier transform infrared (FT-IR) spectroscopy. The binding constants and binding sites of MA to BSA at different reaction times were calculated. And the distance between MA and BSA was estimated to be 5.20 nm based on Föster's theory. In addition, synchronous fluorescence and FT-IR measurements revealed that the secondary structures of the protein changed after the interaction of MA with BSA. As a conclusion, the interaction between the anti-diabetes Chinese medicine MA and BSA may provide some significant information for the mechanism of the traditional chinese medicine MA on the protein level to cure diabetes or other diseases.     

Molecular interactions of plant and algal polysaccharides

This article presents an overview of the interaction in solution of certain plant and algal polysaccharides with cations and also of their interaction in admixture with other polysaccharides and proteins. The mechanism of gelation of pectin and alginate in the presence of calcium ions is discussed together with the specific binding of potassium ions to kappa carrageenan and its influence on the coil–helix transition. The associative and segregative phase behaviour that is encountered in aqueous solutions of mixed polysaccharide systems is considered together with the formation of the soluble and insoluble complexes in mixtures of polysaccharides and proteins.     

Adsorption of Bovine Serum Albumin and Lysozyme on Hydrophobic Calcium Hydroxyapatites

The adsorption of bovine serum albumin (BSA) and lysozyme (LSZ) to oleyl phosphate(OP)-grafted calcium hydroxyapatite (OP-CaHAP) with different degrees of hydrophobicity, ranging the number of surface oleyl group per unit nm2 (nO) from 0 to 2.60, was investigated. The pronounced effects of the hydrophobic moiety of adsorbent on protein adsorption were observed. The saturated amount of adsorbed BSA (ns) was increased up to nO = 0.6 by an enlargement of hydrophobic interaction between hydrophobic CaHAP particle and proteins. However, ns decreased at nO >/= 1.3 by increasing the electrostatic repulsive force between negatively charged BSA and OP-CaHAP particles. On the other hand, the ns value of LSZ was continuously increased up to nO = 2.0 and saturated by increasing either the hydrophobic interaction or the electrostatic attraction of positively charged LSZ and negatively charged OP-grafted CaHAPs. The BSA adsorption experiment revealed that the effect of positively charged adsorption sites on the exposed ac or bc crystal faces (C-sites) of the CaHAPs is screened by the OP-groups grafted on their particle surfaces. Copyright 1999 Academic Press.