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An imbalance in cysteine (Cys) levels in the cells and plasma has been identified as the risk indicator for various human diseases. The structural similarity of cysteine with its congener homocysteine and glutathione offers challenges in its measurement. Herein, we report a hydrogen‐bonded organic‐inorganic framework of Cu(II) (HOIF) for the selective detection of cysteine over other biothiols. The non‐fluorescent HOIF showed 12‐fold green emission in the presence of cysteine. The monomeric unit of HOIF is stabilized via intermolecular hydrogen bonds, resulting in a non‐porous network structure. Non‐interference from homocysteine, glutathione, and other competitive bio‐analytes revealed explicit affinity of HOIF for cysteine. Fluorimetric titration showed a wide working concentration window (650 nM–800 μM) for measuring cysteine in an aqueous medium. The mechanistic investigation involving HRMS, EPR, and UV‐vis spectroscopic studies revealed the decomplexation of HOIF with Cys, resulting in a fluorescence turn‐on response from the luminescent ligand. Validation using a commercial dye, "Cysteine Green", confirmed the prospect of HOIF for early diagnostic purposes. Utilizing the fluorescence turn‐on property of HOIF in the presence of cysteine, we measured cysteine quantitatively in the blood plasma samples. Bio‐imaging of endogenous cysteine in cancer cells indicated the ability of HOIF to monitor the intracellular cysteine. [ABSTRACT FROM AUTHOR]

High levels of unconjugated bilirubin (UB) in serum lead to asymptomatic and neonatal jaundice and brain dysfunctions. Herein, we have reported the detection of UB at as low as 1 μM in an aqueous alkaline medium using a Zn(II) complex. The specificity of the complex has been validated by the HPLC in the concentration window 6–90 μM, which is rare. The sensory response of the probe at physiological pH against nitro explosives developed it as an instant‐acting fluorosensor for picric acid (PA) and 2,4‐dinitrophenol (2,4‐DNP). Spectroscopic titration provided a binding constant of 4×105 M−1 with PA. The naked eye detection was found to be 15 μM. The solid‐state photoluminescent nature of the complex enabled it for PA sensing in the solid phase. Interestingly, the probe remained fluorescent in various volatile and non‐volatile organic solvents. As a result, it can also detect PA and 2,4‐DNP in a wide range of common organic media. NMR studies revealed the coordination of PA, 2,4‐DNP, and UB to the Zn(II) center of the probe, which is responsible for the observed quenching of the probe with the analytes. [ABSTRACT FROM AUTHOR]

Lab-on-a-paper-based devices are promising alternatives to the existing arduous techniques for point-of-need monitoring. The present work reports an instant and facile method to produce a microfluidic paper-based analytical device (μPAD). The fabricated μPAD has been used to detect hypochlorite (OCl−) by incorporating newly synthesized chromo-fluorogenic ratiometric probes 1 and 2 into the sample reception zone. The probes showed high selectivity and fast response (<10 s) toward OCl− with an excellent linear relationship in the concentration range of 0–100 μM. The concentration-dependent fluorometric change driven by the reaction of 1@μPAD with OCl− has been monitored using gel-doc imaging systems, which is unprecedented. Digitizing the intensity of the colour solution with different mathematical models of colour has developed a straightforward method for monitoring OCl− without any interference from its competitors. 1@μPAD can detect OCl− at ∼10 times lower than the WHO recommended limit. The detection limit of 1@μPAD via a digital camera-based fluorescence technique was found to be better over digital camera-based cuvette assays. Therefore, 1@μPAD has been successfully utilized to monitor OCl− in actual environmental water samples with portability, ease of use, and sensitivity. The analytical RSD was found to be ≤3% based on fluorimetric detection using 1@μPAD. The chemodosimetric reaction between OCl− and the probe was evidenced by UV-vis and fluorescence spectroscopy, 1H NMR, and ESI-MS. The rapid response time, biocompatibility, low cytotoxicity, 100% aqueous solubility, ratiometric feature, and exclusive OCl− selectivity over other competitive ROS/RNS successfully lead to the application of the probes for bioimaging of exogenous as well as endogenous OCl− in normal cells (HEK293) and cancerous cells (HeLa). [ABSTRACT FROM AUTHOR]

Fluorescence spectroscopic studies of a pair of new oxido‐vanadium(V) compounds with biological thiols, such as homocysteine (Hcy), cysteine (Cys), and glutathione (GSH), have been investigated in this article. Despite notable progress in vanadium‐thiol chemistry, no attention has been paid to exploring vanadium‐based optical probes to study their interaction with biothiols. For this purpose, two oxido‐vanadium(V) compounds, 1 and 2, have been prepared involving a tridentate ONO donor‐based luminescent coumarin‐derived ligand. Single crystal X‐ray diffraction analysis, NMR (1H, 13C, and 51V) spectroscopy, XPS, and DFT calculations have been used to establish their identities. The vanadium center in these compounds has a distorted octahedral environment. In compound 2, a methanol molecule is coordinated to the vanadium(V) center in the trans position of the terminal oxido moiety. The latter exerts a strong trans‐labilizing influence on the coordinating methanol. Both 1 and 2 are weakly fluorescent. Photophysical investigations of the vanadium complexes in aqueous media at physiological pH (7.4) in the presence of various biothiols and amino acids showed significant fluorescence enhancement (83‐fold) of the vanadium complexes, specifically with Hcy. The specific affinity of the complexes for Hcy remained unchanged even in the presence of other biothiols and amino acids. Kinetic investigation reveals pseudo‐first order behavior of the compound with Hcy. Mechanistic studies have manifested that Hcy‐induced reduction triggers the decomplexation of the vanadium compound, followed by hydrolysis and subsequent cyclization. Time‐correlated single photon counting suggested that the radiative rate constant (kr) of 1 and 2 in the presence of Hcy serves as the prime factor for the fluorescence enhancement of the medium. Compound 1 has been tested efficiently for Hcy measurement in blood plasma rendering it suitable for practical applications. [ABSTRACT FROM AUTHOR]

Abstract: A halotolerant bacterium Acinetobacter soli (MTCC 5918), isolated from the salt farm of our institute, was found to secrete a novel siderophore under iron deprivation conditions. A combination of multinuclear one and two dimensional NMR spectroscopies in conjunction with mass technique revealed that the siderophore, we named acinetoamonabactin (1), is a triscatechol derivative of tris(aminomethyl)methylamine. [ABSTRACT FROM AUTHOR]

Abstract: A series of intramolecularly hydrogen‐bonded zwitterionic compartmental ligands HL1–HL4, containing a pendent diamine arm that is monoprotonated and an aldehyde functionality at two different ortho‐positions of a 4‐halophenoxide, is reported herein. Single‐crystal X‐ray diffraction (SXRD) provides persuasive evidence for the identification of this class of proton‐transferred zwitterions at room temperature. The solid‐state photoluminescent nature of these zwitterions remains intact in aqueous and organic solutions. Grinding of HL1 and HL2 with Cu2+/Ni2+ salts develop turn‐on probes 1–4. Compounds 1 and 4 are dinuclear CuII and NiII species, respectively. Compound 2 is a tetranuclear CuII complex. Interestingly, compound 3 is a mononuclear NiII species in which both nitrogen atoms in the pendant diamine arm are protonated and, therefore, not coordinated to the NiII center. All these probes (1–4) display an instant response to the poison gas hydrogen cyanide (HCN) and cyanide salts present in both solid matrices and aqueous (100 % water) solution. Selective and rapid sensing of HCN gas and cyanide salts in solid/soil/water phases, without any interference, by the mechanosynthesized complexes 1–4 can be perceived easily by the naked eye under a hand‐held UV lamp. [ABSTRACT FROM AUTHOR]

Abstract: Aeruginic acid (H2L), a weakly fluorescent natural ionophore, was synthesized via one‐pot mechanochemical grinding at room‐temperature. This sulfur containing intermediate siderophore showed unique specificity towards Zn2+ in 100% water at physiological pH even in presence of other challenging metal ions particularly, paramagnetic metal ions such as Fe3+, Co2+, Ni2+, and Cu2+. H2L also displayed a naked eye observable instant color change under UV light in presence of Zn2+, in aqueous solution and in solid phase as well. The receptor H2L with 49 nM limit of detection, upon excitation at 360 nm, reversibly binds one equivalent Zn2+ as evidenced from Job's plot, ESI‐MS, and 1H NMR spectroscopy. Being fully water soluble, non‐toxic, and permeable in nature, this natural ionophore can visualize Zn2+ in the gastrointestinal tract of live whole brine shrimp Artemia. We are not aware of any report on bio‐imaging of Zn2+ in living organism. [ABSTRACT FROM AUTHOR]