An Acylhydrazone-Based Fluorescent Sensor for Sequential Recognition of Al3+ and H2PO4−

A novel acylhydrazone-based fluorescent sensor NATB was designed and synthesized for consecutive sensing of Al3+ and H2PO4−. NATB displayed fluorometric sensing to Al3+ and could sequentially detect H2PO4− by fluorescence quenching. The limits of detection for Al3+ and H2PO4− were determined to be 0.83 and 1.7 μM, respectively. The binding ratios of NATB to Al3+ and NATB-Al3+ to H2PO4− were found to be 1:1. The sequential recognition of Al3+ and H2PO4− by NATB could be repeated consecutively. In addition, the practicality of NATB was confirmed with the application of test strips. The sensing mechanisms of Al3+ and H2PO4− by NATB were investigated through fluorescence and UV–Visible spectroscopy, Job plot, ESI-MS, 1H NMR titration, and DFT calculations.

Design and Synthesis of a Fluorescent Probe Based on Copper Complex for Selective Detection of Hydrogen Sulfide

A novel fluorescence probe NA-LCX was rationally designed and synthesized for the sequential recognition of Cu2+ and H2S by the combination of hydroxyl-naphthalene and diformylphenol groups. The response properties of NA-LCX for Cu2+ ions and H2S with “on-off-on” manner were investigated by fluorescence emission spectra. A highly selective and sensitive response of complex NA-LCX-Cu2+ for H2S over other competing amino acids was observed with a limit of detection at 2.79 μM. The stoichiometry of NA-LCX toward Cu2+ ions was determined to be 1 : 1 by the UV-Vis absorption spectrum, and the coordination configuration was calculated by density functional theory (DFT) calculations. Moreover, probe NA-LCX was applied successfully for the recognition of Cu2+ ions and H2S in living cells.

A Novel Highly Sensitive Dual-channel Chemical Sensor for Sequential Recognition of Cu2+ and CN- in Aqueous Media and its Bioimaging Applications on Living Cells

A simple and unique dual-channel chemical probe (DH) was designed and synthesized, which not only realized sequential recognition of Cu2+ and CN− by colorimetric and fluorometric methods, but also realized...

A naked-eye colorimetric sensor based on chalcone for sequential recognition of copper (II) and sulfide in semi-aqueous solution: Spectroscopic and Theoretical approaches

In this study, a simple colorimetric chemosensor based on the chalcone scaffold has been employed for sequential recognition of Cu2+ and S2- ion in a semi-aqueous solution. The chemosensor A01...

Sequential recognition of discrete export signals in flagellar subunits during bacterial Type III secretion

The flagellar T3SS delivers proteins from the bacterial cytosol to nascent cell surface flagella. Early subunits of the flagellar rod and hook are unchaperoned and contain their own export signals. One export signal, the gate recognition motif (GRM) docks subunits at the export gate, which must then open for unfolded subunits to enter the flagellar channel. Here, we identify a second signal at the extreme N-terminus of flagellar rod/hook subunits and determine that key to the signal is its hydrophobicity. We show that the two export signals are recognised sequentially, with the N-terminal signal being recognised only after subunits have docked at the export gate. The position of the N-terminal signal relative to the GRM is important, as a FlgD deletion variant (FlgDshort), in which the distance between the N-terminal signal and the GRM was shortened, stalled at the export machinery and was not exported. The attenuation of motility caused by FlgDshort was suppressed by mutations that destabilised the closed conformation of the FlhAB-FliPQR flagellar export gate, suggesting that the hydrophobic N-terminal signal might trigger gate opening.