Yu-Zhe Chen

BODIPY-Based Ratiometric Fluorescent Sensor for Highly Selective Detection of Glutathione over Cysteine and Homocysteine

We report a ratiometric fluorescent sensor based on monochlorinated BODIPY for highly selective detection of glutathione (GSH) over cysteine (Cys)/homocysteine (Hcy). The chlorine of the monochlorinated BODIPY can be rapidly replaced by thiolates of biothiols through thiol-halogen nucleophilic substitution. The amino groups of Cys/Hcy but not GSH further replace the thiolate to form amino-substituted BODIPY. The significantly different photophysical properties of sulfur- and amino-substituted BODIPY enable the discrimination of GSH over Cys and Hcy. The sensor was applied for detection of GSH in living cells.

Dynamic Covalent Bond Based on Reversible Photo [4 + 4] Cycloaddition of Anthracene for Construction of Double-Dynamic Polymers

Dynamic covalent bonds supplied by reversible anthracene dimerization were combined with pillar[5]arene/imidazole host-guest interactions to construct double-dynamic polymers. Heating such polymers (in solution or as a gel) led to depolymerization by dissociation of either the host-guest complexes alone or the complexes and the anthracene dimers, depending on the extent of heating. The polymers reformed readily upon cooling or irradiation.

A turn-on fluorescent sensor for the discrimination of cystein from homocystein and glutathione

We report a turn-on fluorescent sensor based on nitrothiophenolate boron dipyrromethene (BODIPY) derivatives for the discrimination of cystein (Cys) from homocystein (Hcy) and glutathione (GSH). The sensor was applied for detection of Cys in living cells.

Biological Applications of Supramolecular Assemblies Designed for Excitation Energy Transfer

Excitation Energy Transfer Hui-Qing Peng,† Li-Ya Niu,†,‡ Yu-Zhe Chen,† Li-Zhu Wu,† Chen-Ho Tung,*,†,§ and Qing-Zheng Yang*,†,‡ †Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China ‡Key Laboratory of Radiopharmaceuticals, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, People’s Republic of China Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong, Shandong Normal University, Jinan 250014, People’s Republic of China

Artificial Light‐Harvesting System Based on Multifunctional Surface‐Cross‐Linked Micelles

In the natural photosynthetic centers of bacteria and plants, antenna chromophores absorb solar light and transfer the excitation energy to the reaction center by highly efficient singlet–singlet energy transfer. Spatial organization of individual chromophores is key to such efficiency: chromophores need to be separated enough to minimize selfquenching without sacrificing the dipole–dipole couplingmediated energy transfer. In addition to its important role in photosynthesis, efficient transfer of energy from multiple chromophores to a single acceptor is of potential significance to solar cells, photocatalysts, optical sensors and light-emitting devices. For these reasons, there has been a great deal of interest in mimicking the natural light-harvesting process. A variety of scaffolds have been used including dendrimers, organogels, porphyrin arrays/assemblies, biopolymer assemblies, and organic–inorganic hybrid materials. Although impressive results have been obtained with the above scaffolds, the multistep synthesis of the complex architectures hampers their scale up and widespread application. Nature relies on a combination of covalent and noncovalent interactions to create the photosynthetic centers. Covalent structures possess excellent stability and noncovalent self-assembled constructs provide order and synthetic efficiency. Herein, we report a biomimetic approach to construct artificial light-harvesting systems. We combined two self-assembling strategies and covalent fixation to prepare a highly efficient antenna system from readily available building blocks. The entire synthesis was achieved by a one-pot reaction, and the product precipitated spontaneously out of the reaction mixture at the end of the reaction. The synthesis of the light-harvesting system is shown in Scheme 1, and is based on the recently reported method to cross-link surfactant micelles. Our model antenna chromophore is 9,10-bis(4-methylphenyl)anthracene (DPA), a compound with high fluorescence quantum yield (90%). Eosin Y disodium salt (EY) is the energy acceptor. Cationic surfactant, 4-(dodecyloxy)benzyltripropargylammonium bromide (1), forms micelles at concentrations of above 0.14 mm in water. Because the surface of the micelle is covered with a dense layer of alkynyl groups, 1,4-diazidobutane-2,3-diol (2) could easily capture the micelle by 1,3dipolar cycloaddition with a Cu catalyst. When 1 and 2 were used in a 1:1 ratio, the resulting surface-cross-linked micelles (SCMs) are water-soluble nanoparticles with numerous alkynes on the surface. Surface functionalization occurred readily upon addition of a THF solution of DPA–N3 (obtained from commercially available DPA by partial bromination and azidation, see the Supporting Information). After 18 hours at room temperature, the DPA-functionalized SCMs (DPA– SCMs) precipitated spontaneously from the 2:1 THF/water mixture, apparently as a result of the increased hydrophobicity of the product. The IR spectrum of the DPA–SCMs showed nearly complete disappearance of the alkyne peaks in the starting SCMs (Figure S1, in the Supporting Information). DLS (dynamic light scattering) indicated an increase in size for the SCMs upon DPA-functionalization (Figure S2, in the Supporting Information). The absorption band of the DPA–SCMs is at 330–420 nm in THF and the emission band at 390–520 nm. These spectra match almost exactly with those of the free, monomeric DPA in solution (Figure S3, in the Supporting Information). Therefore, the DPA concentration ([DPA]SCMs) in this system can be determined from the absorption spectrum and the molar coefficient extinction of DPA. A frequent issue in light-harvesting systems with multiple donors is the self-quenching and/or excimer formation caused by the proximity of the chromophores. These pathways interfere with the energy transfer and lower the overall efficiency, and often require elaborate strategies to overcome. Excitingly, the fluorescence quantum yield was 0.80 and 0.90 for the micelle-bound DPA and the free chromophore, respectively (see the Supporting Information). Clearly, neither self-quenching nor excimer formation was significant in the highly crowded system. We suspect there are [*] H.-Q. Peng, Dr. Y.-Z. Chen, Prof. Q.-Z. Yang, Prof. L.-Z. Wu, Prof. C.-H. Tung, Prof. L.-P. Zhang Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry Chinese Academy of Sciences 29 Zhongguancun East Road, Beijing 100190 (China) E-mail: qzyang@mail.ipc.ac.cn H.-Q. Peng, Prof. Q.-X. Tong Department of Chemistry, Shantou University Shantou, Guangdong 515063 (China) E-mail: qxtong@stu.edu.cn

A near-infrared fluorescent sensor for selective detection of cysteine and its application in live cell imaging

Biological thiols, including cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), play important roles in maintaining the appropriate redox status of biological systems. The discrimination between them is of great importance because of their different biological roles. Herein, we present a new near-infrared (NIR) fluorescent sensor Cy-NO2 for selective detection of Cys over Hcy/GSH. The nitrothiophenol group is introduced to quench the fluorescence through photo-induced electron transfer (PET). The sensor undergoes displacement of nitrothiophenol with thiol to turn on the fluorescence. The amino groups of Cys/Hcy further replace the thiolate to form amino-substituted products, which exhibit dramatically different photophysical properties compared to the sulfur-substituted product from the reaction with GSH. By means of more rapid intramolecular displacement of sulfur with the amino group of Cys than Hcy, the discrimination of Cys is achieved. Moreover, Cy-NO2 was successfully applied for bioimaging Cys in living cells.

BODIPY-based fluorescent probe for the simultaneous detection of glutathione and cysteine/homocysteine at different excitation wavelengths

We reported a BODIPY-based fluorescent probe for the simultaneous detection of GSH and Cys/Hcy. The nitrothiophenol moiety of the probe serves not only as a leaving group for the thiol-substitution reaction, but also a fluorescence quencher to provide a low emission background. The electron-withdrawing imidazolium group drastically increases reactivity of the Cys/Hcy-induced substitution–rearrangement reaction. The imidazolium group can further be replaced by GSH and resulted in a bithioether-product (λabs = 568 nm, λem = 588 nm), which showed distinct photophysical properties from the amino-product (λabs = 443 nm, λem = 530 nm) in the case of Cys/Hcy. It is noted that they exhibited great differences in absorption spectra of more than 120 nm. Thus, the simultaneous detection of GSH and Cys/Hcy can be achieved at different excitation wavelengths. The probe can quantitatively determinate the amount of Cys, Hcy and GSH in certain concentration ranges. We also found that the probe could detect GSH and Cys in living cells from different emission channels.

Light-Harvesting Systems Based on Organic Nanocrystals To Mimic Chlorosomes

We report the first highly efficient artificial light-harvesting systems based on nanocrystals of difluoroboron chromophores to mimic the chlorosomes, one of the most efficient light-harvesting systems found in green photosynthetic bacteria. Uniform nanocrystals with controlled donor/acceptor ratios were prepared by simple coassembly of the donors and acceptors in water. The light-harvesting system funneled the excitation energy collected by a thousand donor chromophores to a single acceptor. The well-defined spatial organization of individual chromophores in the nanocrystals enabled an energy transfer efficiency of 95 %, even at a donor/acceptor ratio as high as 1000:1, and a significant fluorescence of the acceptor was observed up to donor/acceptor ratios of 200 000:1.

BODIPY-based fluorometric sensor array for the highly sensitive identification of heavy-metal ions.

A BODIPY(4,4-difluoro-4-bora-3a,4a-diaza-s-indacene)-based fluorometric sensor array has been developed for the highly sensitive detection of eight heavy-metal ions at micromolar concentration. The di-2-picolyamine (DPA) derivatives combine high affinities for a variety of heavy-metal ions with the capacity to perturb the fluorescence properties of BODIPY, making them perfectly suitable for the design of fluorometric sensor arrays for heavy-metal ions. 12 cross-reactive BODIPY fluorescent indicators provide facile identification of the heavy-metal ions using a standard chemometric approach (hierarchical clustering analysis); no misclassifications were found over 45 trials. Clear differentiation among heavy-metal ions as a function of concentration was also achieved, even down to 10(-7)M. A semi-quantitative interpolation of the heavy-metal concentration is obtained by comparing the total Euclidean distance of the measurement with a set of known concentrations in the library.

Synthesis of a Photoresponsive Cryptand and Its Complexations with Paraquat and 2,7-Diazapyrenium

A McMurry coupling reaction was used for the efficient synthesis of a bis(m-phenylene)-32-crown-10 based cryptand Z-3 with high yield. This photoresponsive cryptand formed host-guest complexes with paraquat derivative 4 and 2,7-diazapyrenium derivative 5. Z-3, and E-3 exhibited similar binding affinity to the small guest 4, while dramatic changes were observed in the binding affinity to the large guest 5.