带正电荷蛋白在纳米/微米草酸钙晶体上的吸附特性及其与带负电荷蛋白吸附的比较

研究尺寸分别为100 nm和3 μm的一水草酸钙（COM）和二水草酸钙（COD）晶体对带正电荷的蛋白溶菌酶（LSZ）的吸附差异,并与带负电荷的蛋白牛血清白蛋白（BSA）的吸附进行了比较。LSZ在纳米/微米COM和COD晶体上的吸附都很好的拟合了Langmuir模型,属于单分子层吸附。纳米/微米COM和COD对LSZ的最大吸附量顺序为COD-100 nm >COM-100 nm >COD-3 μm >COM-3 μm;晶体的比表面积越大,曲率越小,晶体表面所带电荷越负,晶体结晶水越多,均导致LSZ吸附量越大。体系离子强度和pH值亦影响LSZ的吸附。随着NaCl浓度增加,LSZ的吸附量减小,说明Na⁺离子能与带正电荷的蛋白LSZ竞争晶体表面的吸附位点,导致晶体表面吸附LSZ的位点减少。晶体对LSZ的最大吸附量都出现在LSZ的等电点附近（pH=10.7）;在pH=5~8（生理条件）时,LSZ的吸附量随pH值的增大而增大。本文结果提示,通过减小尿液的pH值或者适当增大尿液的离子强度,可以减小LSZ在尿微晶上的吸附量,有可能达到抑制草酸钙结石的效果。     

纳米/微米一水草酸钙、二水草酸钙对牛血清白蛋白的吸附性能

研究了牛血清白蛋白(BSA)在尺寸分别为100 nm、3μm的一水草酸钙(COM)和二水草酸钙(COD)晶体上的吸附等温线及晶体ζ电位随BSA浓度(cBSA)的变化。结果表明,4种晶体对BSA的最大吸附量顺序为COD-100 nmCOM-100 nm≥COD-3μmCOM-3μm,即吸附量与晶体的比表面积成正相关。而比表面积归一化后,吸附量顺序为COD-3μmCOM-3μmCOM-100 nmCOD-100 nm,说明COM和COD晶体的结晶水数量和晶面电荷密度影响了BSA的吸附。吸附等温线都很好地拟合了Langmuir模型,表明BSA在纳米/微米COM、COD晶体上的吸附属于单分子层吸附。COM和COD等电点大小顺序为COM-100 nm(7.2)COD-100 nm(6.7)≥COM-3μm(4.7)COD-3μm(4.3),因此在病生理条件下(p H≈6.3)纳米级晶体的团聚比微米级晶体的更严重。纳米级和微米级晶体对BSA的最大吸附量都在BSA等电点附近(p H=4.8)。BSA在纳米/微米COM和COD晶体上的吸附与晶体的比表面积、晶面电荷、团聚、结晶水数量和pH值有关。本文结果有助于阐明尿液中不同性质微晶与尿蛋白质对草酸钙结石形成的影响。     

阴离子、阳离子和非离子表面活性剂在纳/微米草酸钙晶体上的吸附差异

研究了尺寸分别为50 nm和3μm的一水草酸钙(COM)和二水草酸钙(COD)晶体对不同电荷表面活性剂的吸附差异,包括阴离子型表面活性剂磺基琥珀酸钠二辛酯(AOT)、阳离子型表面活性剂十六烷基三甲基溴化铵(CTAB)和非离子型表面活性剂壬基酚聚氧乙烯醚(NP-40),探究了尿液中带不同电荷的分子对纳米、微米尿微晶的影响。结果表明,表面活性剂的吸附量大小为AOTCTABNP-40,即阴离子型表面活性剂的吸附量最大,非离子型表面活性剂的吸附量最小;晶体尺寸相同时,COM的吸附能力稍大于COD;吸附表面活性剂后,晶体表面的ζ电位绝对值都增大,有利于抑制晶体的团聚和沉降。提出了晶体吸附不同表面活性剂的分子模型。不同电荷表面活性剂与纳/微米COM、COD晶体之间存在不同的相互作用。表面活性剂吸附量越大,沉降越慢,对晶体悬浮液的稳定效果越明显。     

阴离子、阳离子和非离子表面活性剂在纳/微米草酸钙晶体上的吸附差异

目的：研究尺寸分别为50 nm和3 μm的一水草酸钙（COM）和二水草酸钙（COD）晶体对不同电荷表面活性剂的吸附差异,包括阴离子型表面活性剂磺基琥珀酸钠二辛酯（AOT）、阳离子型表面活性剂十六烷基三甲基溴化铵（CTAB）和非离子型表面活性剂壬基酚聚氧乙烯醚（NP-40）,探究尿液中带不同电荷的分子对纳米、微米尿微晶的影响。方法：测定不同表面活性剂在纳/微米COM、COD晶体上的吸附量;采用ζ电位仪测定吸附不同表面活性剂后晶体表面的ζ电位;检测加入不同表面活性剂后悬浮液的沉降系数。结果：表面活性剂的吸附量大小为AOT > CTAB > NP-40,即阴离子型表面活性剂的吸附量最大,非离子型表面活性剂的吸附量最小;晶体尺寸相同时,COM的吸附能力稍大于COD;吸附表面活性剂后,晶体的ζ电位绝对值都增大,有利于抑制晶体的团聚和沉降。提出了晶体吸附不同表面活性剂的分子模型。结论：不同电荷表面活性剂与纳/微米COM、COD晶体之间存在不同的相互作用。表面活性剂吸附量越大,沉降越慢,对晶体悬浮液的稳定效果越明显。     

纳米、微米一水草酸钙和二水草酸钙对非离子表面活性剂NP-40的吸附差异

为探究CaO_x结石的形成机理,测定了不同浓度NP-40(c_NP-40)存在下各尺寸COM或COD晶体的吸附量;采用X射线衍射和红外光谱研究吸附前后晶体是否发生晶相改变;采用ζ电位仪测定吸附后晶体表面的ζ电位随c_NP-40的变化。结果表明:不同尺寸COM、COD对NP-40的吸附能力大小顺序为:50 nm > 100 nm > 1μm > > 3μm > 10μm;相同尺寸的晶体,COM的吸附量大于COD。随着c_NP-40增加,3μm和10μm的COM、COD晶体的吸附曲线为S型,而50 nm、100 nm、1μm的COM、COD晶体的吸附曲线为直线型。加入NP-40后,ζ电位绝对值与各晶体的吸附密度成正相关。提出了草酸钙晶体吸附NP-40的分子模型。晶体尺寸越小,对NP-40的吸附量越大。非离子表面活性剂虽然自身不带电荷,但吸附到COM、COD晶体表面后可以通过位阻斥力来增加晶体悬浮液的稳定性,有利于抑制草酸钙结石的形成。     

纳米、微米一水草酸钙和二水草酸钙对非离子表面活性剂NP-40的吸附差异

测定了不同浓度NP-40(c_NP-40)存在下各尺寸COM或COD晶体的吸附量;采用X射线衍射和红外光谱研究吸附前后晶体是否发生晶相改变;采用ζ电位仪测定吸附后晶体表面的ζ电位随c_NP-40的变化。结果表明:不同尺寸COM、COD对NP-40的吸附能力大小顺序为:50 nm > 100 nm > 1 μm >> 3 μm > 10 μm;相同尺寸的晶体,COM的吸附量大于COD。随着c_NP-40增加,3 μm和10 μm的COM、COD晶体的吸附曲线为S型,而50 nm、100 nm、1 μm的COM、COD晶体的吸附曲线为直线型。加入NP-40后,ζ电位绝对值与各晶体的吸附密度成正相关。提出了草酸钙晶体吸附NP-40的分子模型。晶体尺寸越小,对NP-40的吸附量越大。非离子表面活性剂虽然自身不带电荷,但吸附到COM、COD晶体表面后可以通过位阻斥力来增加晶体悬浮液的稳定性,有利于抑制草酸钙结石的形成。     

玉米须提取液对尿液中草酸钙晶体形成的影响

本文采用X射线衍射(XRD)、红外光谱(FTIR)、扫描电子显微镜(SEM)等方法分析了玉米须提取液对正常人尿液中草酸钙晶体形成的影响,通过电导率法研究了草酸钙晶体生长的动力学过程,以及从生物矿化的角度对玉米须提取液影响尿液中草酸钙晶体的可能机理进行了探讨。由于玉米须提取液中有机酸或多糖的羟基、羰基等通过配位作用与Ca²⁺结合形成可溶性配位化合物,减少了Ca²⁺与Oxa^2-的结合能力,从而抑制了CaOxa的成核和生长。同时,可能由于玉米须提取液中有效成分与二水草酸钙(COD)的吸附点键合,增强了COD晶体在溶液中的热力学稳定性,进而抑制了COD晶体向热力学更稳定态的一水草酸钙(COM)晶体转变。结果显示,这种抑制作用随玉米须浓度增大而增大,且COD晶体尺寸随着玉米须浓度的增大而减小。玉米须抑制COD晶体向COM晶体转变的作用为开发预防和治疗尿结石的药物提供了启示。     

二水草酸钙的热力学转化及海藻多糖的稳定作用

草酸钙结石的形成与尿液中草酸钙的存在形式密切相关，一水草酸钙(COM)促进尿石症形成，而二水草酸钙(COD)易随尿液排出体外。本文采用体外模拟方法，比较研究了COD晶体在水溶液、正常人尿液和结石患者尿液3个不同体系中的稳定性及海藻龙须菜多糖(SPS)对COD的稳定作用。在水溶液和患者尿液中，不但COD转化率高，而且得到的转化产物COM晶体聚集程度大；而在正常人尿液中，COD转化率低，转化产物聚集程度较小。COD在不同体系中转化的速度依次为：水溶液＞患者尿液＞正常人尿液。从海藻龙须菜中提取的硫酸多糖可以稳定COD的存在并减小COM的聚集，这有利于阻止草酸钙结石的形成，因此，海藻龙须菜多糖有可能用于防止草酸钙结石形成。     

沙苑子提取液对不同体系中草酸钙晶体生长影响的研究

通过与水、氯化钠、正常人尿液体系的比较,重点研究了结石患者尿液体系中加入中药沙苑子提取液对草酸钙晶体生长的的影响,利用SEM,FTIR和XRD等测试手段对所得晶体进行表征。结果发现:在结石患者尿液体系中形成的草酸钙晶体为一水草酸钙(COM)晶体,而在这4种体系中加入沙苑子提取液后,只形成二水草酸钙(COD)晶体,表明沙苑子提取液能抑制COM晶体生长,并且随着沙苑子提取液浓度增大,抑制作用增强。沙苑子抑制草酸钙晶体生长的可能机理进行了探讨。     

不同晶相的草酸钙晶体引起肾上皮细胞的毒性差异

采用扫描电子显微镜(SEM)、激光共聚焦显微镜(LSM)、流式细胞仪、电感耦合等离子体发射光谱仪(ICP)等方法比较研究了尺寸约1.2μm的一水草酸钙(COM)和二水草酸钙(COD)晶体对非洲绿猴肾上皮细胞(Vero细胞)的损伤差异。COM和COD均能引起Vero细胞的细胞活力和超氧化物歧化酶(SOD)活力降低、丙二醛(MDA)含量升高以及碘化丙啶(PI)红染细胞数目增多,且均呈现浓度依赖性。在相同晶体浓度时,COM的细胞毒性明显比COD强,引起细胞表面表达的粘附分子透明质酸(HA)比COD多,粘附量也显著增加。相比于COM晶体,Vero细胞更容易内吞COD晶体。COM与COD晶体对肾上皮细胞的毒性差异与晶面的离子密度以及细胞与晶体间的静电作用等因素密切相关。本文结果将有助于从分子水平上和细胞水平上阐释草酸钙结石的形成机理。     

高岭土磁性复合材料表面印迹聚合物选择性吸附分离环丙沙星

以氨基改性的磁性高岭土为基质材料,利用电子转移产生催化剂的原子转移自由基聚合法制备磁性高岭土表面印迹聚合物(MMIPs)。通过FTIR、TEM、TGA、XRD和VSM等方法对其物理化学性质进行表征,其比表面积112 m2·g-1,且具有较好的热稳定性、超顺磁性(Ms=13.365 emu·g-1)。吸附性能研究表明,准二级动力学模型能较好地描述MMIPs对环丙沙星(CIP)吸附动力学行为,Langmuir等温模型能较好地拟合MMIPs对CIP的吸附平衡数据,25℃时MMIPs的单分子层吸附容量为89.36 mg·g-1。选择性实验研究表明,MMIPs对CIP具有较好地选择识别性。结合高效液相色谱分析技术,MMIPs已成功应用于鲜鱼样品中痕量CIP的分离、富集和回收,CIP的回收率为92.15%。     

Protein Adsorption on Derivatives of Hyaluronan

Summary: Serum protein adsorption and fibroblast cell adhesion on photo reactive hyaluronic acid (Hyal-N₃) and its sulfated derivative (HyalS-N₃₎ was analysed using a combination of quartz crystal microbalance (QCM) and cell adhesion assays. There was no significant differences in the amount of protein adsorbed onto the two polymers, however proteins were found to be more loosely bound to HyalS-N₃ compared with Hyal-N₃. Approximately 17% and 31% of the fibronectin interacting with Hyal-N₃ and HyalS-N₃ respectively was found to be irreversibly bound after rinsing with MilliQ water, SDS and urea. Proteins were exposed to the polymers before cell adhesion was monitored for a period of 2 hours in serum free conditions. Minimal cell adhesion was observed on albumin-coated materials as well as serum precoated Hyal-N₃. Precoating the materials with fibronectin enhanced cell adhesion, although HyalS-N₃ experienced higher levels of cell adhesion than Hyal-N₃ and similar results were found for the serum precoated materials.     

Structure of Protein Layers during Competitive Adsorption

The formation of protein layers during competitive adsorption was studied with ellipsometry. Single, binary, and ternary protein solutions of human serum albumin (HSA), IgG, and fibrinogen (Fgn) were investigated at concentrations corresponding to blood plasma diluted 1/100. As a model surface, hydrophobic hexamethyldisiloxane (HMDSO) plasma polymer modified silica was used. By using multiambient media measurements of the bare substrate prior to protein adsorption the adsorbed amount as well as the thickness and refractive index of the adsorbed protein layer could be followedin situand in real time. Under conditions used in these experiments neither IgG nor fibrinogen could fully displace serum albumin from the interface. The buildup of the protein layer occurred via different mechanisms for the different protein systems. Fgn adsorbed in a rather flat orientation at low adsorbed amounts, while at higher surface coverage the protein reoriented to a more upright orientation in order to accommodate more molecules in the adsorbed layer. IgG adsorption proceeded mainly end-on with little reorientation or conformational change on adsorption. Finally, for HSA an adsorbed layer thickness greater than the molecular dimensions was observed at high concentrations (although not at low), indicating that aggregates or multilayers formed on HMDSO plasma polymer surfaces. For all protein mixtures the adsorbed layer structure and buildup indicated that Fgn was the protein dominating the adsorbed layer, although HSA partially blocked the adsorption of this protein. At high surface concentration, HSA/Fgn mixtures show an abrupt change in both adsorbed layer thickness and refractive index suggesting, e.g., an interfacial phase transition of the mixed protein layer. A similar but less pronounced behavior was observed for HSA/IgG. For IgG/Fgn and HSA/IgG/Fgn a buildup of the adsorbed layer similar to that displayed by Fgn alone was observed.     

蛋白质在羟基磷灰石界面吸附的研究

考察了酪蛋白酸钠(sodium caseinate,SC)和乳清分离蛋白(whey protein isolate,WPI)在表面性质不同的3种羟基磷灰石(hydroxyapatite,HA)颗粒上的界面吸附,分析了蛋白质的分子构型和HA颗粒的表面性质等因素对蛋白质在HA界面吸附的影响,重点讨论了SC和WPI肽链上磷酸化丝氨酸基团(phosphorylated serine residues,Ser-P)的数量和分布对吸附差异的影响.通过傅里叶变换红外光谱和表面电位分析发现SC和WPI无法被比表面积较小的HA颗粒有效吸附,但是在有效吸附面积较高的球状纳米HA和棒状微米HA上能够被吸附.Ser-P的存在使得SC在HA界面的吸附量更高、吸附能力更强.Ser-P数量和分布的不同则导致了SC中不同的蛋白组分在HA界面的竞争性吸附:β-酪蛋白在2μmHA界面始终存在优先吸附性;当纳米HA的浓度低于15 mg/mL时,纳米HA界面会优先吸附αs-酪蛋白.     

Protein Adsorption onto Zirconia Modified with Terminally Grafted Polyvinylpyrrolidone

Electroacoustics was used to study SDS-stabilized sunflower oil-in-water emulsions, with oil volume fractions between 2% and 50%. The dynamic mobility of the oil droplets was measured; the size and electric charge on the drops were calculated using formulas derived for dilute and concentrated systems and the results were compared. The relation derived for concentrated systems appears to be valid up to at least 50% provided the particles remain within the size range of the instrument, which shifts upward with rising concentration. Conductivity and pH had little effect on particle properties in the range studied; higher oil volume fraction (φ) had a substantial influence on the particle size produced in a homogenizer, but not on the zeta potential. Both median size and spread decreased with increases in φ. In contrast, both size and charge were hardly affected at volume fractions less than 10%. Dilution of the emulsion with a surfactant solution of the same composition as the water phase changed neither the particle size nor the zeta potential. The temperature of the emulsification process had a significant influence on the particle size but the zeta potential was hardly affected. Surfactant concentration had some effect on size at low volume fractions but not for φ>10%. The electroacoustic method hence could be applied to analyze both the dilute and the concentrated emulsions directly. Copyright 2001 Academic Press.     

Lecithin Treatment to Prevent Protein Adsorption onto Contact Lenses

Two types of new never worn lenses made of hydroxyethyl methacrylate (HEMA) were treated with lecithin followed by in vitro immersion into individual protein solutions. The amount of protein absorbed onto untreated and treated lenses was compared using UV absorption spectroscopy. Basing on the results obtained a conclusion was drawn that lecithin prevented the protein adsorption onto contact lenses, and the lecithin concentration affected the amount of the sorbed protein.