Pyrophosphate-selective fluorescent chemosensor based on 1,8-naphthalimide-DPA-Zn(II) complex and its application for cell imaging

A new zinc(II) complex with a two-dipicolylamine-substituted 1,8-naphthalimide for recognition of pyrophosphate with ratiometrical fluorescence changes in aqueous solution has been synthesized and characterized. Its biological application to monitor the intracellular pyrophosphate (PPi) was successfully demonstrated by the observation that the fluorescence of 1 was enhanced by the presence of the Zn(2+) ion and was quenched by addition of PPi.     

A highly selective and sensitive fluorescence sensing system for distinction between diphosphate and nucleoside triphosphates

Among the numerous chemosensors available for diphosphate (P(2)O(7)(4-), PPi) and nucleoside triphosphates (NTPs), only a few can distinguish between PPi and NTPs. Hence, very few bioanalytical applications based on such selective chemosensors have been realized. We have developed a new fluorescence sensing system for distinction between PPi and NTPs based on the combination of two sensors, a binuclear Zn(II) complex (1·2Zn) and boronic acid (BA), in which one chemosensor (1·2Zn) shows signal changes depending on the PPi (or NTP) concentration, and the other (BA) blocks the signal change caused by NTPs; this system enables the distinction of PPi from NTPs and is sensitive to nanomolar concentrations of PPi. The new sensing system has been successfully used for the direct quantification of RNA polymerase activity.     

A Fluorescence Sensor Array Based on Zinc(II)-Carboxyamidoquinolines: Toward Quantitative Detection of ATP**

The newly prepared fluorescent carboxyamidoquinolines ( 1 – 3 ) and their Zn(II) complexes ( Zn@1-Zn@3 ) were used to bind and sense various phosphate anions utilizing a relay mechanism, in which the Zn(II) ion migrates from the Zn@1-Zn@3 complexes to the phosphate, namely adenosine 5’-triphosphate (ATP) and pyrophosphate (PPi), a process accompanied by a dramatic change in fluorescence. Zn@1-Zn@3 assemblies interact with adenine nucleotide phosphates while displaying an analyte-specific response. This process was investigated using UV-vis, fluorescence, and NMR spectroscopy. It is shown that the different binding selectivity and the corresponding fluorescence response enable differentiation of adenosine 5’-triphosphate (ATP), adenosine 5’-diphosphate (ADP), pyrophosphate (PPi), and phosphate (Pi). The cross-reactive nature of the carboxyamidoquinolines-Zn(II) sensors in conjunction with linear discriminant analysis (LDA) was utilized in a simple fluorescence chemosensor array that allows for the identification of ATP, ADP, PPi, and Pi from 8 other anions including adenosine 5’-monophosphate (AMP) with 100 % correct classification. Furthermore, the support vector machine algorithm, a machine learning method, allowed for highly accurate quantitation of ATP in the range of 5–100 μM concentration in unknown samples with error <2.5 %.     

Cd(II) sensing in water using novel aromatic iminodiacetate based fluorescent chemosensors

[structure: see text]. Compounds 1 and 2 were designed as fluorescent chemosensors for Cd(II). For both, a selective determination of Cd(II) over Zn(II) was achieved. The fluorescence emission of both was pH-independent and switched off between pH 3-11 in 100% water. Whereas the recognition of Cd(II) at pH 7.4 gave rise to the formation of charge-transfer complexes (exciplexes) for both (lambdamax ca. 500 and 506 nm, respectively), the recognition of Zn(II) only switched on the (monomeric) anthracene emission of 2, while for 1 it was red-shifted (lambdamax = 468 nm).     

Turn-on fluorescence sensing of nucleoside polyphosphates using a xanthene-based Zn(II) complex chemosensor

Fluorescence sensing with small molecular chemosensors is a versatile technique for elucidation of function of various biological substances. We now report a new fluorescent chemosensor for nucleoside polyphosphates such as ATP using metal-anion coordination chemistry. The chemosensor 1-2Zn(II) is comprised of the two sites of 2,2'-dipicolylamine (Dpa)-Zn(II) as the binding motifs and xanthene as a fluorescent sensing unit for nucleoside polyphosphates. The chemosensor 1-2Zn(II) selectively senses nucleoside polyphosphates with a large fluorescence enhancement (F/F(o) > 15) and strong binding affinity (K(app) approximately = 1 x 10(6) M(-1)), whereas no detectable fluorescence change was induced by monophosphate species and various other anions. The 'turn-on,' fluorescence of 1-2Zn(II) is based on a new mechanism, which involves the binding-induced recovery of the conjugated form of the xanthene ring from its nonfluorescent deconjugated state which was formed by an unprecedented nucleophilic attack of zinc-bound water. The selective and highly sensitive ability of 1-2Zn(II) to detect nucleoside polyphosphates enables its bioanalytical applications in fluorescence visualization of ATP particulate stores in living cells, demonstrating the potential utility of 1-2Zn(II).     

Mononuclear Zn(II)- and Cu(II)-complexes of a hydroxynaphthalene-derived dipicolylamine: fluorescent sensing behaviours toward pyrophosphate ions

Mononuclear Zn(II)-DPA and Cu(II)-DPA complexes crafted on 2-hydroxy-6-cyanonaphthalene fluorophore selectively recognize PPi over ATP and other anions including inorganic phosphates in aqueous medium, showing turn-on type fluorescence enhancements. Coordination of a hydroxyl group of the fluorophore, directly or in alkoxy form, to the central metal ion is crucial for the sensing processes. Both the complexes elicit a fluorescence increase in a time-dependent fashion.     

A highly selective pyrophosphate sensor based on ESIPT turn-on in water

Pyrophosphate (PPi) is a biologically important target. A binuclear system 3?2Zn is found to selectively recognize PPi, leading to a ratiometric fluorescent sensor at pH 7.4 in water. The binding event triggered a large fluorescence response (～100 nm bathochromic shift) by turning on the excited state intramolecular proton transfer (ESIPT). Detection of PPi released from a PCR experiment indicated that this new probe could be a useful tool in bioanalytical applications.     

A ratiometric fluorescence probe for selective visual sensing of Zn2+

A simple ratiometric fluorescence probe based on vinylpyrrole end-capped bipyridine for the visual sensing of Zn2+ under aqueous physiological pH (6.8-7.4) is described. The fluorophores 3a-c showed strong emission around 537 nm in acetonitrile with a quantum yield of 0.4. In buffered (HEPES, pH 7.2) acetonitrile-water mixture (9:1 v/v), titration of transition metal salts to 3c showed strong quenching of the emission at 547 nm except in the case of Zn2+, which resulted in a red-shifted emission at 637 nm. Alkali and alkaline earth metal salts could not induce any considerable changes to the emission behavior of 3a-c. The binding of Zn2+ was highly selective in the presence of a variety of other metal ions. Though Cu2+ quenches the emission of 3c, in the presence of Zn2+, a red emission prevails, indicating the preference of 3c toward Zn2+. Job plot and Benesi-Hildebrand analysis revealed a 1:1 complexation between the probe and the metal ion. The selective visual sensing of Zn2+ with a red emission is ideally suited for the imaging of biological specimens.     

Dipyrrolylquinoxaline-bridged Schiff bases: a new class of fluorescent sensors for mercury(II)

Novel 2,3-bis(1H-pyrrol-2-yl)quinoxaline-functionalized Schiff bases were prepared and characterized as new fluorescent sensors for mercury(II) ion. The X-ray crystal structures of compounds 4, 5, 4a and 5a were determined. The binding properties of 4 and 5 for cations were examined by UV-vis and fluorescence spectroscopy. The UV-vis and fluorescence data indicate that a 1 : 1 stoichiometric complex is formed between compound 4 (or 5) and mercury(II) ion, and the association constant is (3.81 +/- 0.7) x 10(5) M(-1) for 4 and (3.43 +/- 0.53) x 10(5) M(-1) for 5. The recognition mechanism between compound 4 (or 5) and metal ion was discussed based on their chemical construction and the fluorescence quenching effect when they interact with each other. Competition experiments revealed that compound 4 (or 5) has a highly selective response to mercury(II) ion in aqueous solution.     

Imino-phenolic-pyridyl conjugates of calix[4]arene (L1 and L2) as primary fluorescence switch-on sensors for Zn2+ in solution and in HeLa cells and the recognition of pyrophosphate and ATP by [ZnL2

Pyridyl-based triazole-linked calix[4]arene conjugates, viz. L(1) and L(2), were synthesized and characterized. These two conjugates were shown to be selective and sensitive for Zn(2+) among the 12 metal ions studied in HEPES buffer medium by fluorescence, absorption, and visual color change with the detection limit of ~31 and ~112 ppb, respectively, by L(1) and L(2). Moreover, the utility of the conjugates L(1) and L(2) in showing the zinc recognition in live cells has also been demonstrated using HeLa cells as monitored by fluorescence imaging. The zinc complexes of L(1) and L(2) were isolated, and the structure of [ZnL(1)] has been established by single-crystal XRD and that of [ZnL(2)] by DFT calculations. TDDFT calculations were performed in order to demonstrate the electronic properties of receptors and their zinc complexes. The isolated zinc complexes, viz. [ZnL(1)] and [ZnL(2)], have been used as molecular tools for the recognition of anions on the basis of their binding affinities toward Zn(2+). [ZnL(2)] was found to be sensitive and selective toward phosphate-bearing ions and molecules and in particular to pyrophosphate (PPi) and ATP among the other 18 anions studied; however, [ZnL(1)] was not sensitive toward any of the anions studied. The selectivity has been shown on the basis of the changes observed in the emission and absorption spectral studies through the removal of Zn(2+) from [ZnL(2)] by PPi. Thus, [ZnL(2)] has been shown to detect PPi up to 278 ± 10 ppb at pH 7.4 in aqueous methanolic (1/2 v/v) HEPES buffer.     

两种磺酰胺类化合物的合成及其对Fe3+的氧化-还原荧光“开-关”性质

合成了两种磺酰胺类化合物, 并研究了其荧光性能. 通过它们对金属阳离子的选择性识别实验, 发现其在乙醇水溶液中均对Fe3+有专一性的识别作用, 并在NH2OH·HCl和H2O2的存在下, 两种化合物对Fe3+都具有氧化-还原荧光“开-关”作用.     

A highly selective fluorescent chemosensor for zinc ion and imaging application in living cells

A new 2,6-bis(5,6-dihydrobenzo[4,5]imidazo[1,2-c]quinazolin-6-yl)-4-methylphenol (1) serves as a highly selective and sensitive fluorescent probe for Zn(2+) in a HEPES buffer (50 mM, DMSO:water = 1:9 (v/v), pH = 7.2) at 25 °C. The increase in fluorescence in the presence of Zn(2+) is accounted for by the formation of dinuclear Zn(2+) complex [Zn(2)(C(35)H(25)N(6)O)(OH)(NO(3))(2)(H(2)O)] (2), characterized by X-ray crystallography. The fluorescence quantum yield of the chemosensor 1 is only 0.019, and it increases more than 12-fold (0.237) in the presence of 2 equiv of the zinc ion. Interestingly, the introduction of other metal ions causes the fluorescence intensity to be either unchanged or weakened. By incubation of cultured living cells (A375 and HT-29) with the chemosensor 1, intracellular Zn(2+) concentrations could be monitored through selective fluorescence chemosensing.     

罗丹明类荧光探针的合成及对铜离子的检测

合成了罗丹明类Cu2+荧光增强型分子探针3',6'-双(二乙氨基)-2-(N-乙叉基氨基)螺[异吲哚-1,9'-占吨]-3-酮（RA）,并研究了它的光谱性能及对铜离子的识别作用.在乙腈/水（体积比1/1）的介质中,当加入Cu2+后探针RA显玫瑰红色,最大吸收波长为548 nm,最大发射波长为571 nm,且荧光强度显著增强,但是,其它常见离子如Na+, K+, Mg2+, Ca2+, Mn2+, Cd2+, Cr3+, Co2+, Ni2+, Ag+, Pb2+, Zn2+, Fe3+, Hg2+不引起或引起很小的紫外/可见或荧光光谱变化.RA的选择性荧光增强主要是由于Cu2+诱导分子中的酰胺闭环结构发生开环,导致分子结构的共轭程度增大.在6.5×10-8～2.9×10-6 mol?L-1范围内RA可以有效检测Cu2+,检测限为5.0×10-8 mol?L-1.RA对Cu2+的识别不可逆,而且探针RA对pH值不敏感,可以在比较宽的范围内（pH=4.1～10.5）高灵敏、高选择性检测Cu2+.     

Ratiometric Fluorescent Determination of the Zinc Ion Using a Terpyridine Derivative

Zinc is essential for normal growth and development, and hence selective recognition and detection for zinc has been a significant area of research. Here 4′-(4-methoxyphenyl)-2,2′:6′,2″-terpyridine is described for the ratiometric fluorescence quantification of zinc ion with high selectivity. The fluorescence of 4′-(4-methoxyphenyl)-2,2′:6′,2″-terpyridine at 406?nm was quenched in the presence of zinc, and a new emission band appeared at 452?nm. The ratiometric method for the determination of zinc ion was based on the dual fluorescence measurements at 406 and 452?nm. This fluorescence response is caused by the formation of a 1:1 complex between 4′-(4-methoxyphenyl)-2,2′:6′,2″-terpyridine and the zinc(II) ion. The analytical figures of merit for the protocol were obtained. The linear dynamic range extended for zinc concentrations from 3.0 to 40.0?µmol/L with a limit of detection of 0.28?µmol/L. Zinc was determined in water with satisfactory results.     

基于间苯二甲酰腙的荧光探针的合成及其接力识别Al3+和焦磷酸根

设计合成了一种基于2-羟基-1-萘甲醛和间苯二甲酰肼的简单高效的荧光探针L,其结构通过~1H NMR、~(13)C NMR和HRMS进行表征。在乙醇-水(1∶1)的体系中,L能够高选择性识别铝离子,表现出明显的荧光增强,并具有较低的检测限(5. 924×10~(-6)mol/L),二者结合比为1∶2。此外,原位生成的配合物L-2Al~(3+)可接力识别焦磷酸根(PPi),具有良好的选择性和灵敏度,检测限可达4. 756×10~(-5)mol/L。该荧光探针具有潜在的应用价值。     

Ion imprinted sol-gel nanotubes membrane for selective separation of copper ion from aqueous solution

Selective separation of Cu(II) ions from aqueous solution was accomplished with a new type of ion-imprinted silica nanotube membrane. A study on its capability for adsorption and selective recognition showed that best selectivity coefficient over Zn(II) ion was over 150, which is much higher than those of control silica nanotube membranes. The largest relative selectivity coefficient over Zn(II) was >200. The new membrane also possess a fast kinetics for the removal of Cu(II) from aqueous solution, an equilibrium period of <30 min, and suitability for repeated use. Hence, the new membrane acts as an effective material for highly selective preconcentration and separation of Cu(II) ion.     

基于羟苯基苯并咪唑的Zn2+比率荧光探针

通过羰基将两分子2-(4-氨基-2-羟苯基)苯并咪唑(4-AHBI)连接,合成了结构高度对称的新化合物N,N′-二-[3-羟基-4-(2-苯并咪唑)苯基]脲(C27H20N6O3,1),测试了不同溶剂条件下1的紫外吸收和荧光发射光谱,研究了1对Zn2+的选择性识别作用。结果表明,随着溶剂极性的增大,1的紫外吸收峰发生蓝移,激发态分子内质子转移(ESIPT)荧光发射峰明显增强。与4-AHBI相比,1在乙腈溶液中的紫外吸收强度增强约3.5倍,最大吸收峰红移8 nm,荧光发射增强8倍多。1在乙腈溶液中的Zn2+荧光响应行为表明1与Zn2+的结合将导致1在445 nm处的荧光强度不断降低,而在395 nm处出现的新峰的荧光强度不断增强,具有比率荧光探针的特点,而且检测范围较宽,可达1×10-6-1×10-2 mol.L-1。     

Terpyridine Metal Complexes as Building Blocks for Supramolecular Assemblies and Polymers: Thermal Stabilities and Thin Film Preparation

5,5'-Dimethyl-2,2':6',2'-terpyridine complexes with various transition metal ions like Zn(II), Co(II), Mn(II) and Hg(II) were investigated concerning their thermal properties. A significant dependency of the thermal stability (5% weight loss) of the complexes depending on the kind of metal ion used could be observed ranging from 315 to 390 °C. Furthermore, self-assembled thin films of such metallo-supramolecular Hg(II) complexes were prepared and characterized by synchrotron based X-ray reflectivity and fluorescence techniques.     

A metal-organic framework with highly polar pore surfaces: selective CO2 adsorption and guest-dependent on/off emission properties

A 3D porous Zn(II) metal-organic framework {[Zn(2)(H(2)dht)(dht)(0.5)(azpy)(0.5)(H(2)O)]·4H(2)O} (1; H(2)dht=dihydroxyterphthalate, azpy=4,4'-azobipyridine) has been synthesised by employing 2,5-dihydroxyterephthalic acid (H(4)dht), a multidentate ligand and 4,4'-azobipyridine by solvent-diffusion techniques at room temperature. The as-synthesised framework furnishes two different types of channels: one calyx-shaped along the [001] direction and another rectangle-shaped along the [101] direction occupied by guest water molecules. The dehydrated framework, {[Zn(2)(H(2)dht)(dht)(0.5)(azpy)(0.5)]} (1') provides 52.7% void volume to the total unit-cell volume. The pore surfaces of 1' are decorated with unsaturated Zn(II) sites and pendant hydroxyl groups of H(2)dht linker, thereby resulting in a highly polar pore surface. The dehydrated framework 1' shows highly selective adsorption of CO(2) over other gases, such as N(2), H(2), O(2) and Ar, at 195 K. Photoluminescence studies revealed that compound 1 exhibits green emission (λ(max)≈530 nm) on the basis of the excited-state intramolecular proton-transfer (ESIPT) process of the H(2)dht linker; no emission was observed in dehydrated solid 1'. Such guest-induced on/off emission has been correlated to the structural transformation and concomitant breaking and reforming of the OH···OCO hydrogen-bonding interaction in the H(2)dht linker in 1'/1.