Weijiang He

Visible Light Excitable Zn2+ Fluorescent Sensor Derived from an Intramolecular Charge Transfer Fluorophore and Its in Vitro and in Vivo Application

The UV- and sensor-induced interferences to living systems pose a barrier for in vivo Zn(2+) imaging. In this work, an intramolecular charge transfer (ICT) fluorophore of smaller aromatic plane, 4-amino-7-nitro-2,1,3-benzoxadiazole, was adopted to construct visible light excited fluorescent Zn(2+) sensor, NBD-TPEA. This sensor demonstrates a visible ICT absorption band, a large Stokes shift, and biocompatibility. It emits weakly (Phi = 0.003) without pH dependence at pH 7.1-10.1, and the lambda(ex) and lambda(em) are 469 (epsilon(469) = 2.1 x 10(4) M(-1) cm(-1)) and 550 nm, respectively. The NBD-TPEA displays distinct selective Zn(2+)-amplified fluorescence (Phi = 0.046, epsilon(469) = 1.4 x 10(4) M(-1) cm(-1)) with emission shift from 550 to 534 nm, which can be ascribed to the synergic Zn(2+) coordination by the outer bis(pyridin-2-ylmethyl)amine (BPA) and 4-amine. The Zn(2+) binding ratio of NBD-TPEA is 1:1. By comparison with its analogues NBD-BPA and NBD-PMA, which have no Zn(2+) affinity, the outer BPA in NBD-TPEA should be responsible for the Zn(2+)-induced photoinduced electron transfer blockage as well as for the enhanced Zn(2+) binding ability of 4-amine. Successful intracellular Zn(2+) imaging on living cells with NBD-TPEA staining exhibited a preferential accumulation at lysosome and Golgi with dual excitability at either 458 or 488 nm. The intact in vivo Zn(2+) fluorescence imaging on zebrafish embryo or larva stained with NBD-TPEA revealed two zygomorphic luminescent areas around its ventricle which could be related to the Zn(2+) storage for the zebrafish development. Moreover, high Zn(2+) concentration in the developing neuromasters of zebrafish can be visualized by confocal fluorescence imaging. This study demonstrates a novel strategy to construct visible light excited Zn(2+) fluorescent sensor based on ICT fluorophore other than xanthenone analogues. Current data show that NBD-TPEA staining can be a reliable approach for the intact in vivo Zn(2+) imaging of zebrafish larva as well as for the clarification of subcellular distribution of Zn(2+) in vitro.

Design and Synthesis of a Ratiometric Fluorescent Chemosensor for Cu(II) with a Fluorophore Hybridization Approach

A new ratiometric fluorescent sensor for Cu(2+), WLN, has been developed via integrating a 1,8-naphthalimide fluorophore with 8-aminoquinoline. WLN exhibits a highly selective ratiometric response to Cu(2+) over other transition metal ions in aqueous media. Moreover, its practical ratiometric imaging ability for intracellular Cu(2+) has been confirmed in human breast adenocarcinoma cells (MCF-7 cells) using a confocal microscope.

Rational design of a dual chemosensor for cyanide anion sensing based on dicyanovinyl-substituted benzofurazan.

A dicyanovinyl-substituted benzofurazan derivative (C1) was prepared as an efficient ratiometric chemosensor for cyanide anion detection in aqueous acetonitrile solution. Mechanism studies suggested that the nucleophilic addition of cyanide to the α-position of the dicyanovinyl group blocked the ICT progress of C1 and induced remarkable emission and absorption shift.

A new ratiometric and colorimetric chemosensor for cyanide anion based on Coumarin–hemicyanine hybrid

A hybrid coumarin-hemicyanine dye, Cou-BT, was developed as a new ratiometric and colorimetric sensor for cyanide with a sensing mechanism via nucleophilic addition of cyanide anion to the benzothiolium group. Cou-BT shows high sensitivity and selectivity for cyanide detection over other common anion species in aqueous acetonitrile solution. The calculated pseudo-first-order rate constant for cyanide anion addition was (2.13 ± 0.08) × 10(-2) s(-1) at 298 K, and the detection limit was estimated to be 0.64 μM. The DFT and TDDFT calculation results suggest that the ratiometric and colorimetric sensing behavior of Cou-BT upon its reaction with cyanide was due to the interrupted π-conjugation and blocked ICT progress.

In vitro and in vivo imaging application of a 1,8-naphthalimide-derived Zn2+ fluorescent sensor with nuclear envelope penetrability

A newly developed fluorescent sensor, , shows a specific turn-on response to Zn(2+) and can be excited by visible light. The in situ nuclear Zn(2+) imaging in HeLa and HepG2 cells reveals the nuclear envelope penetrability of the sensor. The specific sensor location in a zebrafish larva was also demonstrated.

A charge transfer type pH responsive fluorescent probe and its intracellular application

A new charge transfer pH fluorescent probe BTP has been prepared by the ethylene bridging of benzothiazole and pyridine. The probe exhibits a specific fluorescent response to pH with a large Stokes shift, and the pH-induced emission enhancement factor (EEF) is about 22-fold when the pH is increased from 3.2 to 5.2. The presence of metal cations such as Na+, K+, Ca2+, Mg2+ and other transition metal cations does not interfere with its fluorescent pH response. In addition, the intracellular pH fluorescent imaging ability of the probe has been confirmed on macrophage cells using a confocal microscope.

Synthesis and fluorescence properties of isoindoline–benzazole-based boron difluoride complexes

In this article, a series of isoindoline–benzazole-based boron difluoride complexes (7–12) were synthesized and characterized. Analysis of the X-ray crystal structures of compounds 7, 8 and 10–12 indicates the existence of π–π stacking and H-bond (F–H–C, O–H–N, N–H–C) interactions. These novel boron complexes exhibit large Stokes shifts (3300–8400 cm−1) and moderate quantum yields (0.15–0.64). Time-dependent DFT (TD-DFT) calculations reveal that the maximum absorption bands for 7–12 are attributed to the HOMO → LUMO transitions, and that the calculated absorption wavelengths agree well with the experimental trends.

In Vitro and in Vivo Fluorescent Imaging of a Monofunctional Chelated Platinum Complex Excitable Using Visible Light

The biological fluorescent distribution of a model antitumor monofunctional platinum(II) complex bearing a 7-nitro-2,1,3-benzoxadiazole fluorophore can be visualized in breast carcinoma MCF-7 cells, pulmonary carcinoma A549 cells, kidney epithelial 293T cells, and zebrafish larva.

His-oriented peptide hydrolysis promoted by cis-[Pt(en)(H2O)2]2+: a new specific peptide cleavage site.

The new specific hydrolysis of histidine-containing peptides promoted by cis-[Pt(en)(H(2)O)(2)](2+) was investigated by electrospray ionization mass spectrometry (ESI-MS) and nuclear magnetic resonance spectrometry (NMR). MS determination demonstrated that cis-[Pt(en)(H(2)O)(2)](2+) anchors to AcGHG with the stoichiometry of either 1:1 or 2:1 (Pt/peptide), but only with 1:1 stoichoimetry to AcGHL. Cis-[Pt(en)(H(2)O)(2)](2+) is able to promote the cleavage of the first downstream peptide bond from histidine at 60 degrees C and pH 2.65, and Pt-anchored peptides are the essential intermediates for the promoted hydrolysis. Moreover, the larger amount of Pt(II) complex results in higher fragmental yield and higher hydrolysis rate. In the presence of 1 equiv of Pt(II) complex, (1)H NMR determination confirmed the apparent first-order kinetics of the Pt(II)-promoted hydrolysis and the hydrolysis rate for AcGHG and AcGHL is 0.20 day(-1) and 0.14 day(-1), respectively. Moreover, Pt(II) coordinating to histidine imidazole is the key step to form the Pt(II)-anchored peptides. The Pt(II)-activating the first His-downstream carbonyl group via synergic coordinating to His imidazole and carbonyl O atom has been proposed for the Pt(II)-promoted his-oriented peptide hydrolysis. The lower rate for AcGHL should be correlated to the steric hindrance of Leu side chain to the second Pt(II) coordinating to tripeptide. In addition, the newly confirmed specific His-oriented peptide cleavage site implies a new potential strategy for target cleavage of peptides or proteins.

Synthesis and Properties of New Thiacalixarene Derivatives with Palladium Ion

Three new thiacalix[4]arene derivatives, 5,11,17,23-tetra-tert-butyl-25,27-di(2-hydroxyethoxy)-26,28-dihydroxythiacalix-{}[4]arene (2), 5,11,17,23-tetra-tert-25, 26,27,28-tetrakis[(methylcarboxyl)methoxy]thiacalix[4]arene (3),5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(2-hydroxy-1-propanoxy)thiacalix[4]arene (4), were synthesized for the first time. The coordination properties of thiacalix[4]arene(1) and its derivatives (2 and 4) were investigated by detecting the interactions betweenthese compounds and two palladium complexes, cis-[Pd(en)(H2O)2]2+ and cis-[Pd(dtco-3-OH)(H2O)2]2+, by means of electrospray ionization mass spectrometry (ESI-MS) technique.