-
-
-
-
-
-
-
[show abstract]
[hide abstract]
ABSTRACT: High-tech pH paper: A "chameleon" pH probe composed of rhodamine (red, see scheme) and fluorescein (green) units emits at wavelengths of 580 nm and 512 nm, where the intensities show a contrary response to pH changes. Confocal microscopy of HeLa cells with this probe reveals red and green spots; the ratio of these signals can be calibrated to give the pH value of the respective organelle.
Angewandte Chemie International Edition 04/2013; · 13.45 Impact Factor
-
Chemical Reviews 04/2013; · 40.20 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We present here, the design, synthesis, spectroscopic characterization, and in vitro biological assessment of a gemcitabine-coumarin-biotin conjugate (5). Probe 5 is a multifunctional molecule composed of a thiol-specific cleavable disulfide bond, a coumarin moiety as a fluorescent reporter, gemcitabine (GMC) as a model active drug, and biotin as a cancer targeting unit. Upon addition of free thiols that are relatively abundant in tumor cells, disulfide bond cleavage occurs, as well as active drug GMC release and concomitantly fluorescence intensity increases. Confocal microscopic experiments reveal that 5 is preferentially taken up by A549 cells rather than WI38 cells. Fluorescence-based colocalization studies using lysosome- and endoplasmic reticulum-selective dyes suggest that thiol-induced disulfide cleavage of 5 occur in the lysosome possibly via receptor mediated endocytosis. The present drug delivery system (DDS) is a new theranostic agent, wherein both a therapeutic effect and drug uptake can readily monitored at the subcellular level by two photon fluorescence imaging.
Journal of the American Chemical Society 03/2013; · 9.91 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The multitopic ion-pair receptor is able to recognize and extract various cesium and potassium salts via three different ion recognition modes. Furthermore, it is capable of extracting and then releasing KNO(3)via ion-pair metathesis with CsClO(4), allowing KNO(3) recovery.
Chemical Communications 02/2013; · 6.17 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: On the basis of 1H NMR spectroscopic analyses and single crystal X-ray crystal structural data, the ion pair receptor 1, bearing a calix[4]pyrrole for anion binding and calix[4]arene crown-5 for cation recognition, was found to act as a receptor for both CsF and KF ion pairs. Both substrates are bound strongly but via different binding modes and with different complexation dynamics. Specifically, exposure of to KF in 10% CD3OD in CDCl3 leads first to complexation of the K+ cation by the calix[4]arene crown-5 moiety. Then, as the relative concentration of KF increases the calix[4]pyrrole subunit binds the F- anion. Once bound, the K+ cation and the F- anion give rise to a stable 1:1 ion pair complex that generally precipitates from solution. In contrast to what is seen with KF, the CsF ion pair interacts with receptor 1 in two different modes in 10% CD3OD in CDCl3. In the first of these, the Cs+ cation interacts with the calix[4]arene crown-5 ring weakly. In the second interaction mode, which is thermodynamically more stable, the Cs+ cation and the counter anion, F-, are simultaneously bound to the receptor framework. Further proof that system 1 acts as a viable ion pair receptor came from the finding that receptor 1 could extract KF from an aqueous phase into nitrobenzene, overcoming the high hydration energies of the K+ and F- ions. It was more effective in this regard than a 1:1 mixture of the constituent cation and anion receptors (4 and 5).
Journal of the American Chemical Society 12/2012; · 9.91 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We synthesized a new probe, Mito-Naph, to visualize mitochondrial thioredoxin (Trx) activity in cells. A fluorescence off-on change is induced by disulfide cleavage of the probe, resulting from a reaction with Trx and subsequent intramolecular cyclization by the released thiolate to give a fluorescent product. By measuring the fluorescence at 540 nm, Trx activity can be detected at nanomolar concentrations (down to 50 nM) well below its physiological levels. The in vitro and in vivo Trx preference of Mito-Naph was demonstrated by fluorometric and confocal microscopic experiments. In vitro kinetic analysis of the disulfide bond cleavage revealed that the second-order rate constant for Trx is (4.04 ± 0.26) × 10(3) (M s)(-1), approximately 5000 times faster than that for GSH. The inhibition experiments involving PX-12, a selective inhibitor of Trx, also revealed that the emission from Mito-Naph significantly decreased in PX-12 dose-dependent manners, both in living cells and in cellular protein extracts. The Trx preference was further supported by an observation that the fluorescence intensity of rat liver extract was decreased according to the Trx depletion by immunoprecipitation. On the basis of these results, it is concluded that Mito-Naph preferentially reacts with Trx, compared with other biological thiols containing amino acids in vitro and in vivo.
Journal of the American Chemical Society 09/2012; 134(41):17314-9. · 9.91 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We have synthesized a series of coumarins (1-3) that can emit fluorescence in a turn-on manner through a Michael-type reaction with thiol-containing compounds. The only difference among the coumarins is the position of a carboxyl group on its benzene ring moiety near the double-bond conjugated coumarin. Their selectivity for Cys, GSH, and Hcy as well as the associated fluorogenic mechanism were illustrated by fluorescence spectroscopy, DFT calculations, and kinetic studies. All isomers prefer Cys over GSH in the reaction from 48.6 (probe 3) to 111-fold (probe 1) as demonstrated in a second order kinetics. The high selectivity of probe 1 to Cys might be achieved since the ortho carboxyl group on its benzene ring prefers a less negatively charged nucleophile. During intracellular Cys detection using 1, a possible interference by a large amount of GSH in the HepG2 cells was evaluated. The cells were treated with l-buthionine sulfoximine (BSO), an inhibitor of γ-glutamylcysteine synthetase, providing an experimental condition where the cells could not synthesize GSH from Cys or other species. Then, the fluorescence intensity of 1 in HepG2 cells under BSO-H(2)O(2) treatment was strongly enhanced by N-acetylcysteine (NAC), a precursor of Cys, implicating that the fluorescence signal from the cells is mainly associated with changes in intracellular [Cys] rather than that in intracellular [GSH].
Biomaterials 08/2012; 33(33):8495-502. · 7.40 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A weakly donating group (n-propyl) has been used as a substituent at the para-position of the phenyl group for a series of phenylethynylpyrene derivatives where the number of phenylethynyl peripheral arms appended to the pyrene core is varied. This system markedly improved the concurrent stability of both cation and anion radicals and consequently greatly improved electrogenerated chemiluminescence (ECL). Density functional theory (DFT)-based theoretical calculations supported the associated photophysical and electrochemical properties of the series compounds.
The Journal of Organic Chemistry 08/2012; · 4.45 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A novel ferrocene-based anion receptor bearing amide and triazolium donor groups and its anion complexation have been reported. We found that it shows marked electrochemical selectivity to F(-), followed by AcO(-) > Cl(-) > Br(-) > I(-), which is in accordance with (1)H NMR titration results.
The Analyst 08/2012; 137(19):4454-7. · 4.23 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Presented here is a multicomponent synthetic strategy that allows for the direct, fluorescence-based monitoring of the targeted cellular uptake and release of a conjugated therapeutic agent. Specifically, we report here the design, synthesis, spectroscopic characterization, and preliminary in vitro biological evaluation of a RGD peptide-appended naphthalimide pro-CPT (compound 1). Compound 1 is a multifunctional molecule composed of a disulfide bond as a cleavable linker, a naphthalimide moiety as a fluorescent reporter, an RGD cyclic peptide as a cancer-targeting unit, and camptothecin (CPT) as a model active agent. Upon reaction with free thiols in aqueous media at pH 7.4, disulfide cleavage occurs. This leads to release of the free CPT active agent, as well as the production of a red-shifted fluorescence emission (λ(max) = 535 nm). Confocal microscopic experiments reveal that 1 is preferentially taken up by U87 cells over C6 cells. On the basis of competition experiments involving okadaic acid, an inhibitor of endocytosis, it is concluded that uptake takes place via RGD-dependent endocytosis mechanisms. In U87 cells, the active CPT payload is released within the endoplasmic reticulum, as inferred from fluorescence-based colocalization studies using a known endoplasmic reticulum-selective dye. The present drug delivery system (DDS) could represent a new approach to so-called theragnostic agent development, wherein both a therapeutic effect and drug uptake-related imaging information are produced and can be readily monitored at the subcellular level. In due course, the strategy embodied in conjugate 1 could allow for more precise monitoring of dosage levels, as well as an improved understanding of cellular uptake and release mechanisms.
Journal of the American Chemical Society 05/2012; 134(30):12668-74. · 9.91 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The binding properties of four amido derivatives of p-tetraphenyl tetrahomodioxacalix[4]arene towards alkali and alkaline-earth metal cations using UV-absorption spectrophotometry,
1H NMR and ESI-mass spectrometry techniques are reported.
Journal of Inclusion Phenomena 04/2012; 66(1):153-161. · 1.89 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Reported are the crystal and solution structures (determined by X-ray crystallography and EPR spectroscopy/simulation of the
EPR spectra, respectively) of two dinuclear CuII complexes, coordinated to isomeric dinucleating azetidine-based ligands, whose N3 cavities (pyridine/azetidine/secondary amine) are bridged by para- or meta-substituted phenyl groups. The CuII sites in the two dinuclear systems are similar to each other and as expected from the known structure of the corresponding
mononuclear complex. The significant differences between the crystal structures of the mono- and the two dinuclear complexes
and between the crystal and the solution structures are due to the elasticity of the CuII coordination sphere, the flexibility of the dinucleating ligands and subtle changes related to weak interactions (crystal
lattice, solvation, anion coordination/ion pairing).
Journal of Inclusion Phenomena 04/2012; 65(1):59-64. · 1.89 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: AbstractNew fluorogenic calixazacrown (5) bearing two pyrene amide pendent groups has been synthesized. Based on ratiometric changes of monomer and excimer emissions,
5 has been found to act as a selective sensor for Pb2+ ion due to conformational change upon chelation of Pb2+ within 1:1 complex.
Graphical Abstract
Journal of Inclusion Phenomena 04/2012; 66(1):133-137. · 1.89 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Iron-substituted MCM-41 materials (Fe-MCM-41) have been synthesized via a hydrothermal method with in situ incorporation of
Fe(III) oxalate complex under various basic conditions. The resulting Fe-MCM-41 samples were characterized by X-ray diffraction,
N2 adsorption measurement, and UV–Vis spectrometry. By controlling initial synthesized pH, the Fe-MCM-41 with highly ordered
hexagonal mesoporous structures and high iron content (Si/Fe=20) could be obtained. The iron species in Fe-MCM-41 samples
mainly coexisted in isolated iron and highly dispersed iron oxide nanoclusters. Activity and stability of the obtained catalyst
were evaluated on the wet peroxide oxidation of phenol under mild reaction conditions (<80°C, ambient pressure). The Fe-MCM-41
with highly ordered mesoporous structure and high Fe content appeared to be the most interesting catalysts for phenol degradation
owing to its high organic mineralization, low sensitivity to leaching Fe out and good oxidant efficiency.
Journal of Inclusion Phenomena 04/2012; 65(1):73-81. · 1.89 Impact Factor
