3,3‘,5,5‘-Tetramethyl-N-(9-anthrylmethyl)benzidine: A Dual-Signaling Fluorescent Reagent for Optical Sensing of Aliphatic Aldehydes

Development and application of a high throughput assay system for the detection of Rieske dioxygenase activity

Herein we report the development of a new periodate-based reactive assay system for the fluorescent detection of the cis-diol metabolites produced by Rieske dioxygenases. This sensitive and diastereoselective assay system successfully evaluates the substrate scope of Rieske dioxygenases and determines the relative activity of a rationally designed Rieske dioxygenase variant library. The high throughput capacity of the assay system enables rapid and efficient substrate scope investigations and screening of large dioxygenase variant libraries.

Diverse applications of TMB-based sensing probes

Extending the research on 3,3',5,5'-tetramethylbenzidine (TMB) and its derivatives in analytical chemistry is important, considering that TMB is widely used as an enzyme catalytic substrate. In this work, two TMB derivatives, TMBS and TMBB, were synthesized via a facile and one-step condensation reaction between the -NH2 group of TMB and the -CHO group of salicylaldehyde or benzaldehyde. Because at low pH the two Schiff base compounds can release TMB which can emit strong fluorescence, the probes could show dual-modal signal responses, fluorescence and UV-vis absorption, towards the pH. Practical applications of pH sensing in Chinese rice vinegar and lemon juice samples were successfully demonstrated. On the basis of these findings, a catalytic chromogenic reaction was developed to monitor the pH with the naked eye, too. Furthermore, considering the chemical equilibrium reaction between CO2 and H2O and that glucose oxidase (GOD) can catalyse the dehydrogenation and oxidation reaction of β-d-glucose to produce gluconic acid, both of which can result in lowering the pH values of the two Schiff base systems, highly sensitive and selective dual-modal sensing systems for detecting CO2 and β-d-glucose have also been successfully established. Therefore, the two synthesized TMB derivatives can demonstrate their robust application potential.

A mitochondria-targeting time-gated luminescence probe for hypochlorous acid based on a europium complex

A europium complex-based mitochondria-targeting probe has been developed for the time-gated luminescence imaging of hypochlorous acid in living samples.

Lanthanide complex-based luminescent probes for highly sensitive time-gated luminescence detection of hypochlorous acid

Two novel lanthanide complex-based luminescent probes, ANMTTA-Eu(3+) and ANMTTA-Tb(3+) {ANMTTA, [4'-(4-amino-3-nitrophenoxy)methylene-2,2':6',2"-terpyridine-6,6"-diyl] bis(methylenenitrilo) tetrakis(acetic acid)}, have been designed and synthesized for the highly sensitive and selective time-gated luminescence detection of hypochlorous acid (HOCl) in aqueous media. The probes are almost nonluminescent due to the photoinduced electron transfer (PET) process from the 4-amino-3-nitrophenyl moiety to the terpyridine-Ln(3+) moiety, which quenches the lanthanide luminescence effectively. Upon reaction with HOCl, the 4-amino-3-nitrophenyl moiety is rapidly cleaved from the probe complexes, which affords strongly luminescent lanthanide complexes HTTA-Eu(3+) and HTTA-Tb(3+) {HTTA, (4'-hydroxymethyl-2,2':6',2"-terpyridine-6,6"-diyl) bis(methylenenitrilo) tetrakis(acetic acid)}, accompanied by the remarkable luminescence enhancements. The dose-dependent luminescence enhancements show good linearity with detection limits of 1.3 nM and 0.64 nM for HOCl with ANMTTA-Eu(3+) and ANMTTA-Tb(3+), respectively. In addition, the luminescence responses of ANMTTA-Eu(3+) and ANMTTA-Tb(3+) to HOCl are pH-independent with excellent selectivity to distinguish HOCl from other reactive oxygen/nitrogen species (ROS/RNS). The ANMTTA-Ln(3+)-loaded HeLa and RAW 264.7 macrophage cells were prepared, and then the exogenous HOCl in HeLa cells and endogenous HOCl in macrophage cells were successfully imaged with time-gated luminescence mode. The results demonstrated the practical applicability of the probes for the cell imaging application.

Colorimetric Signaling of Large Aromatic Hydrocarbons via the Enhancement of Aggregation Processes

[graph: see text] In this paper, the use of aggregation processes in squaraine derivatives as signaling protocols in the development of colorimetric probes for certain neutral guest (aromatic hydrocarbons) has been studied.

Determination of aliphatic aldehydes by liquid chromatography with pulsed amperometric detection

An electrochemical detection method for short-chain saturated and unsaturated aliphatic aldehydes separated by liquid chromatography in moderately acidic medium is described. A triple-step waveform of the potentials applied to the polycrystalline platinum electrode, is proposed for sensitive detection of aliphatic aldehydes in flowing streams avoiding tedious pre- or post-column derivatization and/or cleanup procedures. The influences of the perchloric acid concentration and dissolved oxygen in the mobile phase, on the amperometric and chromatographic performance were evaluated and considered in terms of sensitivity and selectivity. Under the optimised experimental conditions (i.e., deoxygenated 50mM HClO4) the proposed analytical method allowed detection limits between 0.2 microM for acrolein and 2.5 microM for valeraldehyde. Regression analysis of calibration data indicates that responses for all investigated compounds are linear over about 2 orders of magnitude above the LOD, with correlation coefficients >0.990. The method was successfully applied to the determination of formaldehyde, acetaldehyde, propionaldehyde and acrolein in real matrices such as spiked water and red wines with good mean recoveries (81-97%).