Preparation and Characterization of Novel Quaternized Cellulose Nanoparticles as Protein Carriers

Quaternized cellulose (QC) nanoparticles were prepared in distilled water by ionic crosslinking of QC with sodium tripolyphosphate (TPP) for the first time. BSA as a model protein drug was used to investigate the loading and release features of the nanoparticles. The results indicated that QC nanoparticles had high loading efficiency and capacity for BSA. The in vitro BSA release of the QC nanoparticles displayed a burst effect in the first 2 h and then a slow continuous release. Nanoparticles with a higher DS of QC showed a decrease in particle size, an increase in zeta potential, a higher loading efficiency and a slower drug‐release profile. These studies demonstrated that QC nanoparticles are potential protein carriers, and that their physicochemical properties and release profile could be easily adjusted.

     

Enhanced optical immunosensor based on surface plasmon resonance for determination of transferrin

Wavelength modulation surface plasmon resonance biosensors (SPR) using colloidal Au nanoparticles and double-linker sensing membrane enhancement are reported for determination of transferrin. The 2-mercaptoethylamine (MEA) was immobilized on the biosensor surface with traditional amine coupling method. The interaction between colloidal Au nanoparticles and MEA was investigated. The anti-transferrin was immobilized on the biosensor surface prepared with staphylococcal protein A (SPA). The interaction of the antibody and antigen was monitored in real time. The good response was obtained in the concentration range 1-20, 0.1-20 and 0.05-20 μg/mL for directly immune assay, double-linker assay and colloidal Au-amplified assay. The result clearly demonstrates that these methods may obtain significantly enhancement of sensitivity for the wavelength modulation SPR biosensor.     

N-辛基-β-D-吡喃葡萄糖苷与BSA相互作用的研究

通过稳态荧光法、紫外-可见光谱法和表面张力法研究了N-辛基-β-D-吡喃葡萄糖苷(OGP)与牛血清白蛋白(BSA)在缓冲液中的相互作用. 根据OGP溶液和OGP/BSA混合溶液的表面张力曲线可以看出, 蛋白质的加入改变了单一表面活性剂溶液的表面张力曲线. 蛋白质的加入还使混合体系的临界胶束浓度(cmc*)大于单一表面活性剂的临界胶束浓度(cmc), 这主要是由于OGP与蛋白质结合减少了单体OGP分子的浓度所致. 加入荧光探针芘测量了OGP和OGP/BSA溶液的I₁/I₃值, 结果也表明BSA的加入增大了OGP的聚集浓度, 其原因与表面张力的变化原因是相同的. 在OGP/BSA体系中, 随着OGP浓度的增大, 紫外吸收减弱、荧光强度有规律的降低, 而且荧光发射峰位发生蓝移, 说明它们的结合部位趋向于Trp残基上|同时通过同步荧光和I^－猝灭实验, 进一步证明了OGP与BSA的结合部位是在BSA的疏水空腔内的色氨酸残基上.     

Gas-assisted magnetic separation for the purification of proteins in batch systems

In this paper, gas-assisted magnetic separation (GAMS), a technique that combines magnetic separation with flotation, was investigated for the potential large-scale separation of proteins. The GAMS process includes adsorption of target proteins and magnetic separation to recover protein-loaded magnetic particles from the dilute biosuspension with the assistance of bubbles. Microsized ethylenediamine-functionalized poly(glycidyl methacrylate) superparamagnetic microspheres (MPMs) and bovine serum albumin (BSA) were used as a model system. The feasibility of GAMS for capturing BSA-loaded MPMs from an appropriate medium was shown. High recovery of BSA-loaded MPMs was obtained by simple adjustment of the initial solution pH without extra detergents and antifoaming agents. The GAMS conditions were consistent with the adsorption conditions, and no proteins were desorbed from the MPMs during this process. Under the optimal conditions, the separation rate and recovery percentage reached 410 mL/min and 98% in 0.61 min, respectively. Conformational changes of BSA during the GAMS process were investigated by fluorescence spectroscopy and circular dichroism spectrometry.     

喹啉类单核锰(Ⅱ)和钴(Ⅱ)配合物的合成、结构、DNA/BSA键合及DNA切割活性

合成了2个结构类似的喹啉类单核锰和钴配合物[ML（H₂O）₃]·H₂O,其中M为Mn（1）、Co（2）,Na₂L为8-（羧基钠甲氧基）喹啉-2-甲酸钠。运用红外光谱、元素分析和X射线单晶衍射表征了其结构。利用电子吸收和发射光谱法研究了配合物与CT-DNA及BSA的键合作用及配合物对DNA的切割作用。晶体解析结果表明2个配合物为同构结构,配合物中心均为七配位的畸变五角双锥结构。钴配合物2与CT-DNA的键合能力强于锰配合物1,两者与BSA的作用机理为静态淬灭机理,而键合常数值大小为1>2。在以H₂O₂作为诱导剂时,在同等条件下,2切割DNA的能力明显增强。通过加入自由基捕获剂证明了配合物对DNA的切割机理为氧化切割机理,其中活性氧为OH·。     

牛血清白蛋白与荧光增白剂相互作用的荧光光谱法研究

应用荧光光谱法研究了牛血清蛋白与荧光增白剂CBS-X、BBU、VBL的相互作用.通过Stern-Volmer方程、Lineweaver-BurK方程和双对数曲线进行计算,研究了FWA对BSA内源荧光的猝灭机制.FWA对BSA内源荧光的猝灭主要为静态猝灭和荧光共振能量转移猝灭.测定了荧光增白剂CBS-X、BBU、VBL对BSA的猝灭常量和扩散常量(283 K),确定了荧光增白剂与BSA结合位点数均为1.根据Frster非辐射能量转移理论,计算了BSA与荧光增白剂分子间的结合距离和能量转移效率.通过测定283 K和298 K时供体与受体分子间结合常量,计算了BSA与荧光增白剂作用的热力学参量.BSA与FWA作用的ΔH<0,ΔS>0,并以此确定了BSA 与荧光增白剂分子主要通过静电力进行作用.     

3-羟基-6-[(4-羧基苯基)偶氮]-苯甲酸与牛血清蛋白结合反应的荧光光谱

采用荧光光谱研究3-羟基-6-[(4-羧基苯基)偶氮]-苯甲酸(HCPAB)与牛血清蛋白(BSA)的相互作用.通过测定298K和310K下HCPAB与BSA的荧光猝灭光谱,计算得到荧光猝灭常数、反应的结合常数、结合位点数及热力学参数,得出这种荧光猝灭机理符合静态猝灭;由Foerster能量转移机理,计算了当BSA与HCPAB比例为1∶1时分子间距离r=3.18nm和能量转移效率E=0.23,并由同步荧光光谱显示HCPAB与BSA的结合位点更接近于色氨酸.     

Synthesis,crystal structure,and interaction with DNA and BSA of a chromium(III) complex with naph-gly Schiff base and 1,10-phenanthroline

A new chromium(III) complex, [CrCl(naph-gly)phen]?H₂O (naph-gly = Schiff base derived from 2-hydroxy-1-naphthaldehyde and glycine, phen = 1,10-phenanthroline), has been synthesized and characterized by elemental analysis, electrospray ionization mass spectroscopy, FT-IR, and X-ray single-crystal diffraction. The chromium(III) complex belongs to the trigonal crystal system, P3(1) space group with crystallographic data: a = b = 1.97017(16) nm, c = 1.02991(7) nm, α?=?β?=?90°, γ =120°, V = 3.4621(5) nm³, D_c = 1.476 g?cm^?3, Z = 6, F(0 0 0)?=?1578, R₁ = 0.0508, wR₂ = 0.0907. There are two independent molecules in the crystallographic asymmetric unit of the chromium(III) complex. Each Cr^III is six-coordinate to form an octahedral geometry. In the crystal, a 3-D structure is formed through intermolecular hydrogen bonds. The calf thymus DNA (CT-DNA)- and bovine serum albumin (BSA)-binding properties of the complex have been studied by UV absorption, fluorescence, and circular dichroism (CD) spectroscopy. Results indicate that the chromium(III) complex binds to CT-DNA in an intercalative mode, and it can bind to BSA and cause conformational changes of BSA.     

Review of recent advances in the preparation of organic polymer monoliths for liquid chromatography of large molecules

In recent years the use of monolithic polymers in separation science has greatly increased due to the advantages these materials present over particle-based stationary phases, such as their relative ease of preparation and good permeability. For these reasons, these materials present high potential as stationary phases for the separation and purification of large molecules such as proteins, peptides, nucleic acids and cells. An example of this is the wide range of commercial available polymer-based monolithic columns now present in the market.     

Generation of anti-azoxystrobin monoclonal antibodies from regioisomeric haptens functionalized at selected sites and development of indirect competitive immunoassays

Azoxystrobin is a modern strobilurin fungicide used around the world to combat prime diseases affecting highly valuable crops. Accordingly, residues of this chemical are frequently found in food, even though mostly under maximum tolerated levels. We herein describe the development of an indirect competitive immunoassay for the determination of azoxystrobin residues. A panel of monoclonal antibodies displaying subnanomolar affinity to azoxystrobin was generated using, as immunizing haptens in mice, four functionalized derivatives carrying the same spacer arm located at different rationally chosen positions. This collection of antibodies was thoroughly characterized with homologous and heterologous antigens, and the immunoassay consisting of monoclonal antibody AZo6#49 and the coating conjugate OVA–AZb6, which displayed an IC₅₀ value of 0.102 μg L⁻¹ and a LOD of 0.017 μg L⁻¹, was eventually optimized. The response to different pH and ionic strength conditions of the specific assay was studied using a biparametric approach. In addition, the influence of Tween 20 and organic solvents over the assay parameters was also evaluated. After optimization, the developed immunochemical assay was applied to the analysis of azoxystrobin in spiked juices of relevant fruits and vegetables, showing excellent recoveries between 2 and 500 μg L⁻¹.