聚集诱导发光材料在聚合物制备及性能检测中的应用进展

聚集诱导发光(AIE)材料因其独特的发光性能,已在荧光检测、生物成像及有机发光器件等领域展现出较为广阔的应用前景。本文综述了AIE材料在监测聚合物制备过程(本体聚合、溶液聚合、乳液聚合及悬浮聚合过程等)中的应用,介绍了利用AIE分子的荧光信号响应检测聚合物玻璃化转变温度、粘度、相分离程度、分子量等物理性能的研究,为AIE材料在聚合过程可视化监测及聚合物荧光功能化领域的应用提供了参考。最后对AIE材料在高分子科学研究中的应用前景进行了展望。     

由自组装构筑蛋白酶响应性近红外/磁共振双显影微球

由分子侧链上修饰近红外荧光分子的聚赖氨酸及表面聚丙烯酸修饰的磁共振显影磁性纳米颗粒为组装单元,采用自组装法构筑了在近红外、磁共振双重显影中均具有蛋白酶响应性的纳米尺度自组装微球.微球形成的组装驱动力为聚赖氨酸侧链氨基与磁性纳米颗粒表面羧基在水相中的静电相互作用,两类组装前驱体在静电力作用下组装为纳米尺度团聚体,再通过戊二醛对氨基的适度交联来构筑胰蛋白酶响应的双显影复合微球.该复合微球处于自组装聚集状态时,微球内近红外荧光分子间的距离减小从而发生荧光共振能量转移,导致荧光分子的自淬灭;而在胰蛋白酶活化后的解组装状态,微球内聚赖氨酸重复单元间的酰胺键被胰蛋白酶切断,荧光分子间距扩大,共振能量转移现象消失,从而导致复合微球在胰蛋白酶存在下释放荧光,荧光释放强度/淬灭强度的比值最高可达18.此外,自组装微球的磁共振显影同样具有胰蛋白酶敏感性,这与组装—解组装过程导致微球内磁性纳米颗粒的局部浓度及聚集状态发生变化有关.细胞和动物实验研究表明,复合微球呈现低细胞毒性,并可特异性地对胰蛋白酶阳性的细胞和组织进行近红外/磁共振双显影,在胰蛋白酶的生物影像学检测中具有潜在的应用前景.     

荧光光谱法研究2,4,6-三氯苯酚与胰蛋白酶的相互作用

运用荧光光谱法研究了2,4,6-三氯苯酚与胰蛋白酶的相互作用。结果表明:2,4,6-三氯苯酚通过静电和疏水作用力与胰蛋白酶形成基态复合物导致胰蛋白酶内源荧光猝灭,猝灭机理主要为静态猝灭。计算了该反应的表观结合常数K、结合位点数n及结合反应的热力学参数,并用同步荧光和三维荧光技术考察了2,4,6-三氯苯酚对胰蛋白酶构象的影响,酪氨酸和色氨酸残基所处微环境的疏水性增加。     

异硫氰酸荧光素-牛血清蛋白-Pb~(2+)“开关”型荧光探针测定尿液中胰蛋白酶

本文研究了"开关"型异硫氰酸荧光素(FITC)-牛血清蛋白(BSA)-Pb2+荧光探针测定胰蛋白酶。实验发现,FITC-BSA探针在Pb2+和十二烷基苯磺酸钠(DBS)存在下,可以发出较强的荧光,此时体系处于"打开"状态。当在pH=7.8的Tris-HCl缓冲溶液中加入胰蛋白酶后,FITC-BSA-Pb2+发生荧光猝灭,探针被"关闭",并且胰蛋白酶的浓度在一定范围内与探针的荧光猝灭程度呈良好的线性关系。实验表明,胰蛋白酶浓度与体系荧光猝灭程度在2.4~24μg/mL间呈良好线性关系,相关系数r=0.9972,方法检出限(3σ/k)为0.80μg/mL。该方法应用于尿液中胰蛋白酶的检测,其相对标准偏差(RSD)≤3.0%,回收率范围为102.1%~106.0%。     

基于羧基化单壁碳纳米角的荧光传感体系检测胰蛋白酶

构建了一种基于羧基化单壁碳纳米角（oxSWCNHs）的简单、灵敏的荧光传感体系用于胰蛋白酶的检测。实验中合成了水溶性的oxSWCNHs,并设计了一段羧基荧光素（FAM）标记肽段作为胰蛋白酶的底物,该底物能与胰蛋白酶进行特异性反应。当体系中没有胰蛋白酶存在时,FAM标记的肽段可以被oxSWCNHs强烈吸附,致使体系具有较低的荧光背景;当体系中有胰蛋白酶存在时,胰蛋白酶可以与其底物肽段发生特异性水解反应,导致FAM标记的肽段水解为单个氨基酸,致使FAM远离oxSWCNHs表面,FAM荧光不能被oxSWCNHs淬灭,体系具有较强的荧光强度,从而实现荧光传感体系对胰蛋白酶的检测。该传感体系线性范围为0～2.5μg/mL,可用于尿液中胰蛋白酶的测定。     

荧光聚合物研究进展

本文总结了近年来荧光聚合物的研究进展,主要介绍了荧光聚合物的分类：按其溶解性能可分为非水溶性、水溶性和两亲荧光聚合物三大类;荧光聚合物的合成：荧光化合物为引发剂、荧光化合物为链转移剂、荧光功能单体聚合、荧光化合物与聚合物的化学键合、非荧光功能单体聚合等五种制备荧光聚合物的设计合成方法;荧光聚合物的应用：荧光聚合物在荧光化学传感器、荧光分子温度计、荧光造影、药物载体、荧光探针等方面的应用研究。     

同步荧光光谱法监测按芳环数分离重质油中的芳烃

采用同步荧光光谱法监测了液相色谱法以氧化铝作固定相将重质油中的芳烃按芳环数分离的分离过程。在同步荧光光谱的监测下，选择了液相色谱分离的合适进样量和分段梯度洗脱溶剂强度，使得减压馏分油和减压渣油中的芳烃都可较好地按芳环数进行分离。     

胰蛋白酶和三种纳米材料相互作用的研究

采用紫外可见、荧光、圆二色光谱法,研究了纳米SiO_2、纳米TiO_2、纳米石墨粉对胰蛋白酶的催化活性及结构的影响。实验表明,三种纳米材料的存在均减弱胰蛋白酶的活性;纳米TiO_2和纳米石墨粉分别通过氢键和范德华力和胰蛋白酶结合从而猝灭酶的内源荧光,纳米SiO_2通过疏水作用猝灭胰蛋白酶的荧光。圆二色光谱研究表明,纳米TiO_2、纳米石墨粉的存在改变了胰蛋白酶的二级结构,纳米SiO_2的存在不改变胰蛋白酶的结构。     

荧光猝灭法结合分子对接研究胰蛋白酶与蒙花苷相互作用

以荧光猝灭法与分子对接为主要研究手段,研究了在模拟生理条件下蒙花苷对胰蛋白酶荧光发射的猝灭作用,并探究了二者之间的相互作用类型与复合物的动力学稳定性。实验结果表明,pH 8.4时在不同温度下蒙花苷均可有效地猝灭胰蛋白酶的荧光发射,并且猝灭类型均为静态猝灭,即蒙花苷与胰蛋白酶间形成了稳定的复合物。使用双对数方程计算可知复合物为1∶1型,根据Van’t Hoff方程对不同温度下蒙花苷猝灭胰蛋白酶的光谱数据分析可知复合物的生成是熵增放热的自发过程。同步荧光光谱结果表明蒙花苷对胰蛋白酶的发光猝灭主要是通过影响其Trp残基的荧光发射实现的。分子对接研究表明蒙花苷可结合在胰蛋白酶表面由His57、Thr98、Gln175、Trp215、Gln192、Ser195等残基所形成的疏水性口袋中,并通过氢键、芳环堆积、疏水、静电吸引等弱作用与胰蛋白酶形成非共价复合物,蒙花苷与Trp215残基间存在明显的疏水与氢键作用,这些作用可减弱这个残基微环境的极性并最终导致其荧光发射的猝灭。30 ns分子动力学模拟表明胰蛋白酶与蒙花苷所形成的复合物具有良好的稳定性,验证了分子对接结果的稳定性和合理性。     

聚环氧乙烷修饰的芘用于“荧光开”检测胰蛋白酶的研究

本文采用聚环氧乙烷(PEO)对疏水染料芘进行亲水化修饰设计,以获得具有良好水溶性和荧光性能的两亲性探针分子聚环氧乙烷修饰的芘(PEO-Py).以牛血清白蛋白(BSA)作为胰蛋白酶的水解底物以及猝灭剂,BSA加入会通过动态猝灭使荧光强度降低.加入胰蛋白酶水解后,荧光强度部分恢复,建立了基于荧光强度升高的“荧光开”胰蛋白酶检测方法.对胰蛋白酶的检测限可达到9.8 μg·mL-1,检测线性范围为0～0.075 mg·mL-1.其他蛋白不会引起荧光强度的降低,检测体系具有良好的选择性.通过亲水化修饰提高了芘衍生物的水溶性,建立了制备简单、成本低、水溶性好的检测探针,拓展了芘在生理环境中的检测应用.     

Enhance effect of surfactants on the photoluminescence and photostability of water-soluble poly(phenylene ethynylene)

The interaction between the water-soluble anionic fluorescence conjugated polyelectrolytes PPESO 3 (poly[2,5-bis(3-sulfonatopropoxy)-1,4-phenylethynylene-alt- 1,4-poly(phenylene ethynylene)]) and various surfactants has been studied in aqueous solution by UV-vis absorption spectra and fluorescence spectra. With the addition of surfactants, the aggregations of polymers are broken up. For eliminating the self-quenching effect of the fluorescent polymers, the photoluminescence of PPESO 3 is dramatically enhanced. The photoluminescence of PPESO 3 can be enhanced 6- to 12-fold with the addition of different surfactants, and at higher concentration of surfactants, the photostability of PPESO 3 is also highly increased. A "micelle incorporation model" is proposed to explain the enhancement of photostability. To deeply understand the interaction processes between PPESO 3 and surfactants, we systematically studied the fluorescence spectra changes of PPESO 3 and the dynamic processes at different CTAB concentrations. All results prove the surfactants can simultaneously enhance the photoluminescence and photostability of water-soluble conjugated polyelectrolytes, and this method is very simple and powerful.     

Amplified quenching of a conjugated polyelectrolyte by cyanine dyes

The conjugated polyelectrolyte PPESO3 features a poly(phenylene ethynylene) backbone substituted with anionic 3-sulfonatopropyloxy groups. PPESO3 is quenched very efficiently (KSV > 10(6) M(-1)) by cationic energy transfer quenchers in an amplified quenching process. In the present investigation, steady-state and picosecond time-resolved fluorescence spectroscopy are used to examine amplified quenching of PPESO3 by a series of cyanine dyes via singlet-singlet energy transfer. The goal of this work is to understand the mechanism of amplified quenching and to characterize important parameters that govern the amplification process. Steady-state fluorescence quenching of PPESO3 by three cationic oxacarbocyanine dyes in methanol solution shows that the quenching efficiency does not correlate with the Forster radius computed from spectral overlap of the PPESO3 fluorescence with the cyanines' absorption. The quenching efficiency is controlled by the stability of the polymer-dye association complex. When quenching studies are carried out in water where PPESO3 is aggregated, changes observed in the absorption and fluorescence spectra of 1,1',3,3,3',3'-hexamethylindotricarbocyanine iodide (HMIDC) indicate that the polymer templates the formation of a J-aggregate of the dye. The fluorescence dynamics in the PPESO3/HMIDC system were probed by time-resolved upconversion and the results show that PPESO3 to HMIDC energy transfer occurs on two distinctive time scales. At low HMIDC concentration, the dynamics are dominated by an energy transfer pathway with a time scale faster than 4 ps. With increasing HMIDC concentration, an energy pathway with a time scale of 0.1-1 ns is active. The prompt pathway (tau < 4 ps) is attributed to quenching of delocalized PPESO3 excitons created near the HMIDC association site, whereas the slow phase is attributed to intra- and interchain exciton diffusion to the HMIDC.     

Determination of catecholamine in human serum by a fluorescent quenching method based on a water-soluble fluorescent conjugated polymer-enzyme hybrid system

In this paper, a sensitive water-soluble fluorescent conjugated polymer biosensor for catecholamine (dopamine DA, adrenaline AD and norepinephrine NE) was developed. In the presence of horse radish peroxidase (HRP) and H(2)O(2), catecholamine could be oxidized and the oxidation product of catecholamine could quench the photoluminescence (PL) intensity of poly(2,5-bis(3-sulfonatopropoxy)-1,4-phenylethynylenealt-1,4-poly(phenylene ethynylene)) (PPESO(3)). The quenching PL intensity of PPESO(3) (I(0)/I) was proportional to the concentration of DA, AD and NE in the concentration ranges of 5.0 × 10(-7) to 1.4 × 10(-4), 5.0 × 10(-6) to 5.0 × 10(-4), and 5.0 × 10(-6) to 5.0 × 10(-4) mol L(-1), respectively. The detection limit for DA, AD and NE was 1.4 × 10(-7) mol L(-1), 1.0 × 10(-6) and 1.0 × 10(-6) mol L(-1), respectively. The PPESO(3)-enzyme hybrid system based on the fluorescence quenching method was successfully applied for the determination of catecholamine in human serum samples with good accuracy and satisfactory recovery. The results were in good agreement with those provided by the HPLC-MS method.     

Purification method for recombinant proteins based on a fusion between the target protein and the C-terminus of calmodulin

Calmodulin (CaM) was used as an affinity tail to facilitate the purification of the green fluorescent protein (GFP), which was used as a model target protein. The protein GFP was fused to the C-terminus of CaM, and a factor Xa cleavage site was introduced between the two proteins. A CaM-GFP fusion protein was expressed in E. coli and purified on a phenothiazine-derivatized silica column. CaM binds to the phenothiazine on the column in a Ca(2+)-dependent fashion and it was, therefore, used as an affinity tail for the purification of GFP. The fusion protein bound to the affinity column was then subjected to a proteolytic digestion with factor Xa. Pure GFP was eluted with a Ca(2+)-containing buffer, while CaM was eluted later with a buffer containing the Ca(2+)-chelating agent EGTA. The purity of the isolated GFP was verified by SDS-PAGE, and the fluorescence properties of the purified GFP were characterized.     

小型微波谐振腔用于蛋白质微波辅助酶解

采用微波谐振腔对细胞色素c以及牛血清白蛋白进行微波辅助酶解, 通过电喷雾三级四极杆质谱对得到的肽段进行分析, 证明该方法可用很低的微波功率将蛋白质彻底酶解为多肽. 通过调整微波条件可以使蛋白质的酶解效率基本达到100％, 细胞色素c和牛血清白蛋白的序列覆盖率分别为45％和26％. 该方法不但可将蛋白酶解时间由传统方法的16 h缩短为20 min, 还将功率由使用微波炉时的数百瓦降至20 W.     

Dendrimers and combinatorial chemistry—tools for fluorescent enhancement in protease assays

FRET based systems are some of the best methods available to detect and monitor proteolytic activity. To enhance fluorescent signals and hence assay sensitivity, two different systems were developed using two different dendrimeric constructs. In the first case, a triple branched dendrimer bearing three dansyl groups was used to enhance assay sensitivity and showed a significant enhancement of fluorescence following enzymatic cleavage. In another example, a tris-fluorescein probe, that undergoes self-quenching, was utilized in a combinatorial library synthesis to map the substrate specificity of proteases.     

A microchip-based proteolytic digestion system driven by electroosmotic pumping

Microchip-based proteomic analysis requires proteolytic digestion of proteins in microdevices. Enzyme reactors in microdevices, fabricated in glass, silicon, and PDMS substrates, have recently been demonstrated for model protein digestions. The common approach used for these enzyme reactors is employment of a syringe pump(s) to generate hydrodynamic flow, driving the proteins through the reactors. Here we present a novel approach, using electroosmotic flow (EOF) to electrokinetically pump proteins through a proteolytic system. The existence of EOF in the proteolytic system packed with immobilized trypsin gel beads was proven by imaging the movement of a neutral fluorescent marker. Digestions of proteins were subsequently carried out for 12 min, and the tryptic peptides were analyzed independently using capillary electrophoresis (CE) and MALDI-TOF mass spectrometry (MS). The results from CE analysis of the tryptic peptides from the EOF-driven proteolytic system and a conventional water bath digestion were comparable. MALDI-TOF MS was used to identify the parent protein and the tryptic peptides using MS-Fit database searching. The potential utility of the EOF-driven proteolytic system was demonstrated by direct electro-elution of proteins from an acrylamide gel into the proteolytic system, with elution and tryptic digestion achieved in a single step. The EOF-driven proteolytic system, thus, provides a simple way to integrate protein digestion into an electrophoretic micro total analysis system for protein analysis and characterization.     

In-capillary self-assembly and proteolytic cleavage of polyhistidine peptide capped quantum dots

A new method using fluorescence coupled capillary electrophoresis (CE-FL) for monitoring self-assembly and proteolytic cleavage of hexahistidine peptide capped quantum dots (QDs) inside a capillary has been developed in this report. QDs and the ATTO 590-labeled hexahistidine peptide (H6-ATTO) were injected into a capillary, sequentially. Their self-assembly inside the capillary was driven by a metal-affinity force which yielded a new fluorescence signal due to Förster resonance energy transfer (FRET). The highly efficient separation of fluorescent complexes and the FRET process were analyzed using CE-FL. The self-assembly of QDs and biomolecules was found to effectively take place inside the capillary. The kinetics of the assembly was monitored by CE-FL, and the approach was extended to the study of proteolytic cleavage of surface conjugated peptides. Being the first in-depth analysis of in-capillary nanoparticle–biomolecule assembly, the novel approach reported here provides inspiration to the development of QD-based FRET probes for biomedical applications.     

A Small‐Molecule FRET Reporter for the Real‐Time Visualization of Cell‐Surface Proteolytic Enzyme Functions

Real‐time imaging of cell‐surface‐associated proteolytic enzymes is critical to better understand their performances in both physiological and pathological processes. However, most current approaches are limited by their complexity and poor membrane‐anchoring properties. Herein, we have designed and synthesized a unique small‐molecule fluorescent probe, which combines the principles of passive exogenous membrane insertion and Förster resonance energy transfer (FRET) to image cell‐surface‐localized furin‐like convertase activities. The membrane‐associated furin‐like enzymatic cleavage of the peptide probe leads to an increased fluorescence intensity which was mainly localized on the plasma membrane of the furin‐expressed cells. This small‐molecule fluorescent probe may serve as a unique and reliable reporter for real‐time visualization of endogenous cell‐surfaceassociated proteolytic furin‐like enzyme functions in live cells and tissues using one‐photon and two‐photon microscopy.     

Different effects of Fe2+ and Fe3+ on conjugated polymer PPESO3: a novel platform for sensitive assays of hydrogen peroxide and glucose

Fe(2+) and Fe(3+) as a redox pair showing different effects on a water-soluble conjugated polymer PPESO(3) is definitely an interesting and useful phenomenon in view of signal transduction and has been utilized to develop sensitive assays of hydrogen peroxide and glucose.