Carbon dots as a fluorescent probe for label-free detection of physiological potassium level in human serum and red blood cells

A unique photoluminescence carbon dots (CDs) with larger size were prepared by microwave-assisted method. Complex functional groups on the surface of the CDs facilitate the nanoparticles to form affinity with some metal ions. Taking advantage of the effective fluorescence quenching effect of K⁺, a highly sensitive CD-based fluorescence analytical system for label-free detection of K⁺ with limit of detection (LOD) 1.0 × 10⁻¹² M was established. The concentrations of potassium ion in biological samples such as human serum are usually found at millimolar levels or even higher. The proposed method begins with a substantial dilution of the sample to place the K⁺ concentration in the dynamic range for quantification, which covers 3 orders of magnitude. This offers some advantages: the detection of K⁺ only needs very small quantities of biological samples, and the dilution of samples such as serum may effectively eliminate the potential interferences that often originate from the background matrix. The determined potassium levels were satisfactory and closely comparable with the results given by the hospital, indicating that this fluorescent probe is applicable to detection of physiological potassium level with high accuracy. Compared with other relative biosensors requiring modified design, bio-molecular modification or/and sophisticated instruments, this CD-based sensor is very simple, cost-effective and easy detection, suggesting great potential applications for successively monitoring physiological potassium level and the change in biological system.     

刷状结构的阳离子性接枝微粒QPDMAEMA/SiO2对牛血清白蛋白的吸附特性

以微米级硅胶微粒为基质, 通过接枝聚合和大分子反应, 制备了具有刷状结构的阳离子性接枝微粒, 深入研究了其对牛血清白蛋白(BSA)的强吸附能力、吸附机理和吸附热力学. 首先使含叔胺基团的单体甲基丙烯酸二甲基氨基乙酯(DMAEMA)在硅胶微粒表面发生接枝聚合, 制得接枝微粒PDMAEMA/SiO₂, 然后以氯乙胺为试剂, 使接枝大分子PDMAEMA链中的叔胺基团发生季铵化反应, 获得了具有刷状结构的阳离子聚电解质的功能接枝微粒QPDMAEMA/SiO₂. 测定了微粒QPDMAEMA/SiO₂的zeta 电位, 实施了对BSA的等温吸附实验, 考察了介质pH值、离子强度及温度对吸附作用的影响, 研究了吸附热力学. 研究结果表明, 功能接枝微粒QPDMAEMA/SiO₂ 比接枝微粒PDMAEMA/SiO₂ 具有更高的zeta 电位, 在静电相互作用驱动下, 微粒QPDMAEMA/SiO₂对BSA具有很强的吸附能力. 吸附容量随介质pH值的增大呈现先增大后减小的变化趋势,当pH值等于BSA的等电点(pI=4.7)时, 具有最高的吸附容量(高达112 mg·g^-1). 以等电点为界, 离子强度对吸附容量会产生完全相反的影响作用: 当介质pH值小于BSA的等电点时, 电解质浓度增大, 吸附容量增高; 当介质pH值等于BSA的等电点时, 吸附容量几乎不随电解质的浓度发生变化. 吸附过程熵值减小而且放出热量,是一个焓驱动的吸附过程.     

Affinity purification of aprotinin from bovine lung

An affinity protocol for the purification of aprotinin from bovine lung was developed. To simulate the structure of sucrose octasulfate, a natural specific probe for aprotinin, the affinity ligand was composed of an acidic head and a hydrophobic stick, and was then linked with Sepharose. The sorbent was then subjected to adsorption analysis with pure aprotinin. The purification process consisted of one step of affinity chromatography and another step of ultrafiltration. Then purified aprotinin was subjected to sodium dodecyl sulfate polyacrylamide gel electrophoresis, trypsin inhibitor activity, gel‐filtration, and thin‐layer chromatography analysis. As calculated, the theoretical maximum adsorption (Q_max) of the affinity sorbent was 25 476.0 ± 184.8 kallikrein inactivator unit/g wet gel; the dissociation constant of the complex “immobilized ligand‐aprotinin” (K_d) was 4.6 ± 0.1 kallikrein inactivator unit/mL. After the affinity separation of bovine lung aprotinin, reducing sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis and gel‐filtration chromatography revealed that the protein was a single polypeptide, and the purities were ～ 97 and 100%, respectively; the purified peptide was also confirmed with aprotinin standard by gel‐filtration chromatography and thin‐layer chromatography. After the whole purification process, protein, and bioactivity recoveries were 2.2 and 92.6%, respectively; and the specific activity was up to 15 907.1 ± 10.2 kallikrein inactivator unit/mg.     

Hydrophobic charge‐induction resin with 5‐aminobenzimidazol as the functional ligand: preparation,protein adsorption and immunoglobulin G purification

A new hydrophobic charge‐induction chromatography resin was prepared with 5‐aminobenzimidazol as functional ligand and polyacrylic ester beads as matrix. Adsorption isotherms and adsorption in columns were investigated using human immunoglobulin G and bovine serum albumin as model proteins, and the influence of pH and NaCl concentration was discussed. Results showed that the ligand density was 195 μmol/mL gel, and protein selectivity can be improved by controlling pH and salt addition. An optimized purification process (sample loading at pH 8.0 with 0.2 M NaCl and elution at pH 5.0) was performed to purify human immunoglobulin G from bovine serum albumin containing feedstock, which resulted in human immunoglobulin G purity of 99.7% and recovery of 94.6%. A similar process was applied for the purification of monoclonal antibody from cell culture supernatant, which showed antibody purity of 94.9% and recovery of 92.5%. The results indicated that the new resin developed had comparable performance as Protein A chromatography and would be suitable for antibody purification from complex feedstock.     

Mn（Ⅱ）与BSA相互作用的热力学特征

运用荧光光谱法研究了锰（Ⅱ,Mn2＋）与牛血清白蛋白（Bovine Serum Albumin,BSA）的相互作用.随着Mn2＋浓度的增大,BSA的荧光强度降低,最大发射峰蓝移2nm,根据Stern-Volmer方程求出了Mn2＋与BSA作用的猝灭常数,其猝灭机制为静态猝灭.根据热力学方程求得了290K和308K时的热力学参数△H、△G和△S,结果表明温度升高Mn2＋与BSA的作用增强,二者之间的作用力主要为疏水作用和静电作用.     

同步荧光法研究溴氰菊酯与牛血清白蛋白的结合作用

用同步荧光法消除了溴氰菊酯对牛血清白蛋白内源性荧光的干扰,研究了生理条件（pH=7.4）下溴氰菊酯与牛血清白蛋白之间的相互作用。不同温度下的猝灭常数证明溴氰菊酯对牛血清白蛋白的猝灭是静态过程,据此求得25℃下溴氰菊酯与牛血清白蛋白的结合常数为1.97×105L.mol-1,热力学参数ΔH=29.79kJ.mol-1、ΔS=201.32J.K-1.mol-1,两者之间的相互作用力以疏水作用力为主。根据Foerster非辐射能量转移机理,计算了牛血清白蛋白与溴氰菊酯间结合距离r=5.42nm,能量转移效率E=0.104。     

肺癌的血清自体荧光检测

激光诱导荧光光谱是一种研究较为广泛的医用光谱技术,已经被用于组织、细胞学的检测.本文利用激光诱导荧光光谱技术,测定了肺癌患者和健康人的血清自体荧光光谱.并采用主成分分析法和判别分析法对荧光光谱数据进行了分析和处理,从大量的光谱数据中提出少量主成分值,并通过主成分值的差别对肺癌的诊断率进行分析.得到的结果为,对肺癌的诊断...     

血清中胆固醇的近红外光谱测量及模型适用性研究

使用近红外光谱分析方法进行了血清中胆固醇含量的快速、无试剂测最研究,并考察、分析了模型的适用性.利用傅里叶光谱仪测量1,2和6.5mm 厚血清的近红外光谱,在合频与第一、第二倍频波段内,结合偏最小二乘方法(PLS)对胆固醇建立了模型.1,2,6.5mm 厚血清模型的预测标准差(RMSEP)分别是0.15,0.16,0....     

维生素B12与牛血清白蛋白相互作用的荧光法研究

用荧光光谱法和紫外吸收光谱法研究了生理条件下维生素B12与牛血清白蛋白之间的相互作用。结果表明,维生素B12对牛血清白蛋白的荧光有猝灭作用,其猝灭过程属于静态猝灭。通过计算得出维生素B12与牛血清白蛋白的结合常数及结合位点数。根据Foerster非辐射能量转移理论,测得维生素B12与牛血清白蛋白的能量转移效率E=0.1091,维生素B12与牛血清白蛋白的结合位置距离212位的色氨酸残基为6.29nm。同时采用同步荧光光谱法研究了维生素B12对牛血清白蛋白构象的影响。     

[Zn（Phen）（5-Fu）_2]（NO_3）_2与牛血清白蛋白相互作用的荧光光谱

以Zn（）为中心离子,5-氟脲嘧啶（5-Fu）和邻菲口罗啉（Phen）为配体,合成了[Zn（Phen）（5-Fu）2]（NO3）2配合物,并利用荧光光谱考察了该配合物与牛血清白蛋白（BSA）的相互作用。实验结果表明,配合物与BSA作用可导致BSA内源荧光猝灭,其猝灭机理为静态猝灭,结合常数Ka=1.56×106L/mol,结合位点数n=1.40,且该配合物能够猝灭BSA分子表面94.0%的色氨酸（Trp）残基,是良好的BSA猝灭剂。