Dabcyl as a Naked Eye Colorimetric Chemosensor for Palladium Detection in Aqueous Medium.

Industrial activity has raised significant concerns regarding the widespread pollution caused by metal ions, contaminating ecosystems and causing adverse effects on human health. Therefore, the development of sensors for selective and sensitive detection of these analytes is extremely important. In this regard, an azo dye, Dabcyl 2, was synthesised and investigated for sensing metal ions with environmental and industrial relevance. The cation binding character of 2 was evaluated by colour changes as seen by the naked eye, UV-Vis and 1H NMR titrations in aqueous mixtures of SDS (0.02 M, pH 6) solution with acetonitrile (99:1, v/v). Out of the several cations tested, chemosensor 2 had a selective response for Pd2+, Sn2+ and Fe3+, showing a remarkable colour change visible to the naked eye and large bathochromic shifts in the UV-Vis spectrum of 2. This compound was very sensitive for Pd2+, Sn2+ and Fe3+, with a detection limit as low as 5.4 × 10-8 M, 1.3 × 10-7 M and 5.2 × 10-8 M, respectively. Moreover, comparative studies revealed that chemosensor 2 had high selectivity towards Pd2+ even in the presence of other metal ions in SDS aqueous mixtures.

Study of the efficiency of chemiluminescence resonance energy transfer system based on hemin/G-quadruplex DNAzyme catalysis by chemiluminescence imaging.

For designing and constructing a highly efficient CRET system, it is extremely important to systematically study the effects of reactants and the catalysts on the efficiency. In this paper, we investigated the effects of reactants and the catalyst hemin/G-quadruplex DNAzyme concentration, donor-acceptor ratio and distance on the CRET efficiency by CL imaging. The CRET system was based on hemin/G-quadruplex DNAzyme catalyzed luminol analogue L012 and hydrogen peroxide CL system, taking luminol analogue L012 as the energy donor and a quenching dye DABCYL labelled on the catalyst hemin/G-quadruplex instead of the donor as the energy acceptor. Our study showed that the concentrations of the CL reactants had no significant effect on the efficiency, while the concentration of the catalyst hemin/G-quadruplex had a great effect on the CRET efficiency. When the ratio of the energy donor to the acceptor was as high as 250, the efficiency was only reduced by 5.1%, which was quite different from that of FRET. In addition, a DNA double-stranded structure was designed at the end of G-quadruplex to control the distance between the donor and the acceptor. When the acceptor DABCYL was separated by different linker lengths (1, 5, 10, 20, and 30 base pairs) from the catalyst and the donor L012 molecules, the corresponding CRET efficiencies were 86.0%, 75.1%, 25.7%, 14.0%, and 5.0%, respectively. CL imaging was successfully used to study the efficiency of CRET with high throughput, low sample consumption, and high sensitivity. Our strategy would be beneficial to design and construct a highly efficient CRET system, enabling the interdisciplinary applications of CRET.

Fluorescent aptasensor based on D-AMA/F-CSC for the sensitive and specific recognition of myoglobin.

A novel fluorescent biosensor based on dabcyl [(E)-4-((4-(dimethylamino) phenyl) diazenyl)benzoic acid] -modified anti-Mb aptamer (D-AMA) and 6-FAM(6-carboxyfluorescein) -modified complementary short chain (F-CSC)for the specific and sensitive detection of Mb levels is presented in this study. In PBS buffer solution, D-AMA bound to F-CSC, and then dabcyl quenched the fluorescence of 6-FAM. After adding Mb into the system, D-AMA bound to Mb and separated from F-CSC. The fluorescence of 6-FAM was restored after it separated from dabcyl. The assay exhibited high specificity and sensitivity toward Mb, with a low limit of detection of 0.07 ng/mL (S/N = 3) and linear relationships of 0.1-5 ng/mL. It was further applied to detect Mb levels in spiked human blood sera samples.

FRET-Protease-Coupled Peptidyl-Prolyl cis-trans Isomerase Assay: New Internally Quenched Fluorogenic Substrates for High-Throughput Screening.

In this work, a sensitive and convenient protease-based fluorimetric high-throughput screening (HTS) assay for determining peptidyl-prolyl cis-trans isomerase activity was developed. The assay was based on a new intramolecularly quenched substrate, whose fluorescence and structural properties were examined together with kinetic constants and the effects of solvents on its isomerization process. Pilot screens performed using the Library of Pharmacologically Active Compounds (LOPAC) and cyclophilin A (CypA), as isomerase model enzyme, indicated that the assay was robust for HTS, and that comparable results were obtained with a CypA inhibitor tested both manually and automatically. Moreover, a new compound that inhibits CypA activity with an IC50 in the low micromolar range was identified. Molecular docking studies revealed that the molecule shows a notable shape complementarity with the catalytic pocket confirming the experimental observations. Due to its simplicity and precision in the determination of extent of inhibition and reaction rates required for kinetic analysis, this assay offers many advantages over other commonly used assays.