Ratiometric Fluorescent Sensor for Silver Ion and Its Resultant Complex for Iodide Anion in Aqueous Solution

In aqueous solution, sensor DQAg can selectively detect Ag+ based on inhibition of the resonance, demonstrating a large hypsochromic shift of 84 nm and remarkable changes in the ratio (F481 nm/F565 nm) of the emission intensity (R/R0 up to 26-fold). Furthermore, the resultant Ag–DQAg also displays a ratiometric and highly selective response to iodide anion over other anions due to the liberation of DQAg from the complex by precipitating AgI

Highly Sensitive and Selective Fluorescent Sensor for Distinguishing Cadmium from Zinc Ions in Aqueous Media

A fluorescent sensor, QA, based on acetamidoquinoline with DPA as receptor, was synthesized. In aqueous buffer solution, QA demonstrates high selectivity for sensing Cd2+ with about 40-fold enhancement in fluorescence quantum yield and picomolar sensitivity (Kd = 0.25 ± 0.03 pM). Moreover, sensor QA can distinguish Cd2+ from Zn2+ via two different sensing mechanisms (PET for Cd2+; ICT for Zn2+), and the discrimination is even possible by “naked eyes”

A General Strategy for the Semisynthesis of Ratiometric Fluorescent Sensor Proteins with Increased Dynamic Range

We demonstrate how a combination of self-labeling protein tags and unnatural amino acid technology permits the semisynthesis of ratiometric fluorescent sensor proteins with unprecedented dynamic range <i>in vitro</i> and on live cells. To generate such a sensor, a binding protein is labeled with a fluorescent competitor of the analyte using SNAP-tag in conjugation with a second fluorophore that is positioned in vicinity of the binding site of the binding protein using unnatural amino acid technology. Binding of the analyte by the sensor displaces the tethered fluorescent competitor from the binding protein and disrupts fluorescence resonance energy transfer between the two fluorophores. Using this design principle, we generate a ratiometric fluorescent sensor protein for methotrexate that exhibits large dynamic ranges both <i>in vitro</i> (ratio changes up to 32) and on cell surfaces (ratio change of 13). The performance of these semisynthetic sensor proteins makes them attractive for applications in basic research and diagnostics

Ratiometric Zn²⁺ Fluorescent Sensor and New Approach for Sensing Cd²⁺ by Ratiometric Displacement

A fluorescent sensor QB, based on quinoline with DPA as receptor, is designed as a ratiometric sensor for Zn2+ and CHEF (chalation enhanced fluorescence) sensor for Cd2+. Moreover, another ratiometric signal output for Cd2+ can be observed when the bound Zn2+ in the QB−Zn2+ complex is displaced by Cd2+. These results demonstrate that QB can act not only as a ratiometirc sensor for Zn2+ but also as a dual-mode Cd2+-selective sensor via the CHEF mechanism and ratiometric displacement

A General Strategy for the Semisynthesis of Ratiometric Fluorescent Sensor Proteins with Increased Dynamic Range

We demonstrate how a combination of self-labeling protein tags and unnatural amino acid technology permits the semisynthesis of ratiometric fluorescent sensor proteins with unprecedented dynamic range in vitro and on live cells. To generate such a sensor, a binding protein is labeled with a fluorescent competitor of the analyte using SNAP-tag in conjugation with a second fluorophore that is positioned in vicinity of the binding site of the binding protein using unnatural amino acid technology. Binding of the analyte by the sensor displaces the tethered fluorescent competitor from the binding protein and disrupts fluorescence resonance energy transfer between the two fluorophores. Using this design principle, we generate a ratiometric fluorescent sensor protein for methotrexate that exhibits large dynamic ranges both in vitro (ratio changes up to 32) and on cell surfaces (ratio change of 13). The performance of these semisynthetic sensor proteins makes them attractive for applications in basic research and diagnostics

Quinoline-Based Fluorescent Probe for Ratiometric Detection of Lysosomal pH

A new pH-responsive fluorescent probe has been reported based on protonation-activable resonance charge transfer. In aqueous solution, probe PQ-Lyso exhibits ratiometric detection of pH changes with a large hypsochromic shift of 76 nm and remarkable changes in the fluorescence intensity ratio (<i>R</i> = <i>F</i>_494 nm/<i>F</i>_570 nm, <i>R</i>/<i>R</i>₀ = 105). Furthermore, PQ-Lyso, which is localized to lysosomes in living cells, can calibrate lysosomal pH using fluorescence ratiometry

Modulating Affinities of Di-2-picolylamine (DPA)-Substituted Quinoline Sensors for Zinc Ions by Varying Pendant Ligands

We have developed a series of di-2-picolylamine (DPA)-substituted quinoline sensors, HQ1–4, bearing a pendant ligand at the 8 position of quinoline. UV–vis spectra of HQ1–4 showed similar variations to that of HQ5 but with different varying extents upon the titration of zinc ions. Fluorescence intensities of HQ1, HQ3, and HQ4 were enhanced 4–6 times upon the addition of 1 equiv of zinc ions under an aqueous buffer. Somewhat unexpectedly, HQ2 is nonfluorescent in the presence of metal ions, including zinc ions. The affinities of HQ sensors are distributed in a broad range from nanomolarity to femtomolarity by varying the pendant ligands near the coordination unit. More importantly, these new sensors exhibited very high selectivity for Zn2+ over Na+, K+, Mg2+, and Ca2+ at the millimolar level and over other transition metal ions at the micromolar level, except for Cd2+. These findings indicated that the incorporations of the pendant groups exerted no effect on the spectroscopic properties and selectivity of the parent fluorescent sensor, with the exception of HQ2. Finally, X-ray crystal structures of ZnHQʼs revealed that the auxiliary pendant groups at the 8 position participated in zinc coordination and were able to tune the affinities of HQ sensors

A Strategy for Highly Selective Detection and Imaging of Hypochlorite Using Selenoxide Elimination

A new strategy for HOCl-specific fluorescent probes has been reported based on a selenoxide elimination reaction. Probes CM1 and CM2 were synthesized as the first fluorescent probes containing an arylseleno moiety for hypochlorite according to this strategy. Both probes displayed excellent properties, including high selectivity and sensitivity, fast response, and pH independency toward hypochlorite in vitro and vivo

Syntheses, Structures, and Characterizations of Two Pairs of Cd(II)-5-Aminotetrazolate Coordination Polymers

Two pairs of Cd(II)-5-aminotetrazolate coordination complexes, {[Cd(5-HATZ)2(H2O)2(μ2-SO4)]·H2O}n (1a) and [Cd5(5-ATZ)4(μ3-OH)2(μ5-SO4)2]n (1b), [Cd(5-HATZ)2(μ2-Cl)2]n (2a), and [Cd3(5-ATZ)4(MeCN)2(μ2-Cl)2]n (2b), have been synthesized and structurally characterized. At room temperature 1D single-bridged and double-bridged chain-like compounds 1a and 2a were isolated by solution evaporation method. Under hydrothermal synthesis at 180 °C, two three-dimensional coordination polymers 1b and 2b were isolated from compounds 1a and 2a, respectively. 1b is constructed by 3D [Cd5(μ5-SO4)2(μ3-OH)2]n4+ network templated by 5-ATZ anions. 2b exhibits the 3D metal-organic framework with a (8.122)(844.122)(42.124) topology. 5-Aminotetrazolate is a terminal ligand in 1a and 2a, whereas it is three-coordinated and/or four-coordinated in 1b and 2b. Thermal studies show that high-dimensional structures have higher thermal stability than that of 1D structures

Two 2-Fold Interpenetrated Frameworks Showing Different Topologies Based on the Isomerous Benzenedicarboxylate Mixed with a Flexible <i>N</i>,<i>N</i>‘-Type Ligand

This paper presents two 2-fold parallel interpenetrated polymers, namely ZnCo(bpp)(m-BDC)2 (1) and Co(bpp)(p-BDC)(2), based on isomerous 1,3-benzenedicarboxylate (m-BDC) and 1,4-benzenedicarboxylate (p-BDC). Compounds 1 and 2 have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction, IR, ICP, TGA, DSC, and element analysis. 1 crystallizes in the triclinic space group P1̄ and affords a three-dimensional (3D) six-connected α-Po network, whereas 2 crystallizes in the orthorhombic space group Pbca and gives an usual 2D four-connected 44 grid. These interpenetrated topologies should be attributed to the high functionality and adaptability of the 1,3-bis(4-pyridyl)propane (bpp) ligand