基于聚合物核壳纳米粒子的Hg~(2+)比率型荧光检测传感器

采用一步聚合的方法,制备了以疏水的聚甲基丙烯酸甲酯(PMMA)为核、亲水性的聚电解质支化聚乙烯亚胺(PEI)为壳的纳米粒子分散液.将供体荧光团4-胺基-7-硝基-N-辛基苯并[1,2,5]噁二唑(NBD)以包埋的方式在聚合过程中直接引入PMMA核内部,而受体荧光团罗丹明衍生物SRHB通过吸附作用进入PEI-PMMA核壳界面,构成了含有两种不同荧光分子且可对Hg2+进行荧光比率检测的传感器.考察了含荧光分子的聚合物粒子光谱学性质,证明两种荧光分子均被引入了聚合物粒子体系.在汞离子的荧光检测试验中,加入Hg2+后,体系中的NBD荧光强度下降,而罗丹明的特征发射峰在579 nm处出现,并随着Hg2+浓度的增加,受体/供体的荧光强度比值呈现增长趋势.研究还发现,聚合物粒子基荧光探针对于Hg2+具有较好的选择性,且最佳使用范围是体系pH值在5～8之间,其检测Hg2+的最低浓度可达到1μmol/L.     

Two-Photon Excited Fluorescence Energy Transfer: A Study Based on Oligonucleotide Rulers

The use of two-photon excitation of fluorescence for detection of fluorescence resonance energy transfer (FRET) was studied for a selected fluorescent donor–acceptor pair. A method based on labeled DNA was developed for controlling the distance between the donor and the acceptor molecules. The method consists of hybridization of fluorescent oligonucleotides to a complementary single-stranded target DNA. As the efficiency of FRET is strongly distance dependent, energy transfer does not occur unless the fluorescent oligonucleotides and the target DNA are hybridized. A high degree of DNA hybridization and an excellent FRET efficiency were verified with one-photon excited fluorescence studies. Excitation spectra of fluorophores are usually wider in case of two-photon excitation than in the case of one-photon excitation [1]. This makes the selective excitation of donor difficult and might cause errors in detection of FRET with two-photon excited fluorescence. Different techniques to analyze the FRET efficiency from two-photon excited fluorescence data are discussed. The quenching of the donor fluorescence intensity turned to be the most consistent way to detect the FRET efficiency. The two-photon excited FRET is shown to give a good response to the distance between the donor and the acceptor molecules.     

An Optical Approach for Drug Screening Based on Light‐Harvesting Conjugated Polyelectrolytes

Drugs turn the light off : Conjugated polyelectrolytes (CPEs) have been used in fluorescent assays for real‐time screening of small molecules that prevent the RNA–protein complexation that is important for virus replication and thereby can be considered potential initial candidates for drug discovery (see picture).

     

Fluorescence Logic‐Signal‐Based Multiplex Detection of Nucleases with the Assembly of a Cationic Conjugated Polymer and Branched DNA

An energy‐transfer cascade is generated from a cationic conjugated polymer (PFP) and negatively charged, Y‐shaped DNA labeled with three dyes at its termini (fluorescein (Fl), Tex Red, and Cy5). Multistep fluorescence resonance energy transfer regulates the fluorescence intensities of PFP and the dyes. Different types of logic gates can be operated by observing the emission wavelengths of different dyes with multiplex nucleases as inputs.

     

Photoswitchable Fluorescent Nanoparticles: Preparation,Properties and Applications

This minireview highlights recent advances of research dedicated to photoswitchable fluorescent nanoparticles and their applications. Recently, several strategies have been developed to synthesize nanoparticles with optically switchable emission properties: either fluorescence on/off or dual‐alternating‐color fluorescence photoswitching. The underlying mechanisms of fluorescence photoswitching enable many different types of photoswitchable fluorescent nanoparticles to change fluorescence colors, thus validating the basis of the initial photoswitching design. Among all possible applications, the usage of photoswitchable fluorescent nanoparticles to empower super‐resolution fluorescence imaging and to label biological targets was subsequently reviewed. Finally, we summarize the important areas regarding future research and development on photoswitchable fluorescent nanoparticles.     

基于FRET机理的荧光探针的合成及其对汞离子的识别

基于FRET机理设计合成了一个包含罗丹明6G及香豆素的汞离子荧光探针Rh-6G-coumarin(RC),研究了它的光谱性能及对汞离子的识别作用。在V(C₂H₅OH)∶V(H₂O)=9∶1溶液中加入汞离子后,575 nm处荧光强度迅速增大,荧光由蓝色变为明亮的红色,同时溶液的颜色由黄色变为红色。溶液中其他金属离子,如Na⁺、K⁺、Mg²⁺、Fe²⁺、Co²⁺、Pb²⁺、Zn²⁺、Cd²⁺和Cr³⁺对汞离子的荧光识别没有太大影响。该探针可在较宽的pH ( 4~10)范围内识别汞离子。光谱滴定实验表明,汞离子与RC以2∶1的计量比形成了配合物。     

Fluorescence Methods to Probe Nanometer-Scale Organization of Molecules in Living Cell Membranes

The ability to study the structure and function of cell membranes and membrane components is fundamental to understanding cellular processes. This requires the use of methods which are capable of resolving structures at nanometer-scale resolution in living cells. In this review we survey fluorescence imaging methodologies capable of nanometer-scale resolution. We then critically examine specific biological applications of these methods, in the context of understanding membrane protein conformation and dynamics, intracellular signaling, organization of lipid rafts, and cell surface topology.     

Studying Spatial Distributions of Influenza Hemagglutinin on the Plasma Membrane of Fibroblasts: A Work in Progress

The major envelope protein of influenza virus, hemagglutinin (HA), mediates the fusion of virus to cell for infection, and can mediate cell-cell fusion. It has been studied as a “raft” protein, as it is found in detergent-resistant membranes (DRM) and trafficks apically in polarized epithelia. Moreover, the viral envelope of influenza itself is rich in sphingomyelin and cholesterol. Using both immunogold electron microscopy and fluorescence resonance energy transfer (FRET) microscopy, we are examining the distribution of HA on the surface of fibroblasts expressing wild-type HA.     

Vesicles displaying aggregation-induced emission: Fabrication and applications

Vesicles displaying aggregation induced emission are very promising in fields related to biology. In this review, we summarized recent progresses in the creation of such vesicles and their applications. The following contents are included: 1) the general background of AIE vesicles; 2) creation of AIE vesicles with synthetic covalent compounds; 3) creation of AIE vesicles with supramolecular chemistry; 4) the application of AIE vesicles in real-time imaging, visualized drug delivery, cell communication and fission-fusion process, and light-harvesting. Finally, we envision AIE vesicles may have profound impact on medical science, biological science and material science.