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A rationally designed Schiff base chemosensor (L) could render specific detection of Al 3+ ions with two distinct turn-on emission signals, separated by over 100 nm upon excitation at two different wavelengths. The utility of the probe lies in facilitating sensing in 80% aqueous medium with an emission close to 600 nm via an intramolecular charge transfer (ICT) mechanism. The biocompatible and cell permeable probe could readily sense Al 3+ in live HeLa cells as well. The affinity of the probe for Al 3+ could be leveraged to specifically study DNA- Al 3+ interaction in solution. [ABSTRACT FROM AUTHOR]

At present, few genetically encoded fluorescent probes are currently available for the analysis of toxic heavy metal ions, and most have poor performance that cannot meet the requirements of sensitive and dynamic detection in living cells. In this study, we designed a single fluorescent protein-based probe sfGFP-MerBD, which can specifically response to Hg2+ with high binding affinity and wide dynamic range. More importantly, the developing probe can timely and reversibly monitor changes of Hg2+ concentration in living mammalian cells. The excellent performance of this probe is largely due to the recognition element of the probe, MerBD, which adopts an unusual planar trigonometric coordination configuration with Hg2+, and the coordination can cause enough conformational change to influence the fluorescence of skeleton protein sfGFP coupled with it. The small peptide MerBD was delicately designed based on the three-dimensional structure of metalloprotein MerR. This novel design strategy solves the challenging problems that there are few natural functional proteins in the process of constructing fluorescent probes for toxic metal ions and some functional proteins cannot be directly used as recognition elements. Based on the new strategy, more genetically encoded fluorescent probes of toxic heavy metal ions can be efficiently constructed and applied in the future. [Display omitted] • Genetically encoded probes are ideal tools in living cellular imaging. • Few genetically encoded probes related for toxic heavy metal are currently available. • Novel strategy is adopted in constructing the probe sfGFP-MerBD for sensing Hg2+. • The probe maintains the unusual planar trigonometric coordination with Hg2+. • The probe responses to Hg2+ with high binding affinity and wide dynamic range. [ABSTRACT FROM AUTHOR]

A rhodamine hydrazide conjugating uridine moiety (RBH-U) is firstly synthesized by screening different synthetic routes, and then developed as a fluorescence probe for selective detection of Fe3+ ions in an aqueous solution, accompanied by visual color change with naked eyes. Upon the addition of Fe3+ in a 1:1 stoichiometry, a 9-fold enhancement in the fluorescence intensity of the RBH-U was observed with an emission wavelength of 580 nm. In the presence of other metal ions, the "turn-on" fluorescent probe with pH-independent (value 5.0 to 8.0) is remarkably specific for Fe3+ with a detection limit as low as 0.34 μM. Further, the enhanced fluorescence intensity of RBH-U- Fe3+ can be quenched as a switch-off sensor to assist in the recognition of Cu2+ ions. Additionally, the colocalization assay demonstrated that RBH-U containing uridine residue can be used as a novel mitochondria-targeted fluorescent probe with rapid reaction time. Cytotoxicity and cell imaging of RBH-U probe in live NIH-3T3 cells suggest that it can be a potential candidate for clinical diagnosis and Fe3+ tracking toll for the biological system due to its biocompatibility and nontoxicity in NIH-3T3 cells even up to 100 μM. [Display omitted] • A novel mitochondria-targeted fluorescent probe (RBH-U) at 580 nm of emission. • Upon the addition of Fe3+ in a 1:1 stoichiometry, a 9-fold fluorescence intensity enhancement is occurred. • The efficient target of mitochondria, and selective recognition of Fe3+ in vivo and Cu2+ in vitro. [ABSTRACT FROM AUTHOR]

Hg(II) is well-known for quenching fluorescence in a distance dependent manner. Nevertheless, when we exposed the fluorophore of a green fluorescent protein (GFP) toward Hg(II), through H148C mutation, the GFP fluorescence could be “lighted up” by Hg(II) down to sub-nM level. The detection linear range is 0.5–3.0 nM for protein solutions at 8.0 nM. The GFPH148C protein displayed a promising selectivity toward Hg(II) and also the cellular imaging capacity. Spectra measurements suggested that the ground-state redistribution of protein contributed to the fluorescence enhancement, which was found not limited to Hg(II), and thus presented an opening for building a pool of GFP-based chemosensors toward other heavy metal ions. [ABSTRACT FROM AUTHOR]

Highlights: [•] The chemosensor 1 developed here performed a ratiometric response to Al3+. [•] Al3+ detection can be undertaken in aqueous solution at neutral pH. [•] The sensor design was transformed into test papers for the detection of Al3+. [•] The application of 1 for Al3+ imaging in live cells was also achieved. [ABSTRACT FROM AUTHOR]

Highlights: [•] A “turn-on” fluorescent chemosensor for the detection of Zn(II) was facilely synthesized. [•] Detection of Zn(II) can be performed in water at neutral pH with high sensitivity. [•] The chemosensor exhibits remarkably selective to Zn(II) over other metal ions. [•] The chemosensor could be efficiently delivered to live cells for bioimaging of Zn(II). [Copyright &y& Elsevier]