Coumarin-Based Noncytotoxicity Fluorescent Dye for Tracking Actin Protein in In-Vivo Imaging.

Drosophila shares maximum homology with the human disease-causing genes and thus has been employed to evaluate the toxicity of numerous compounds. Further, its distinguishable developmental stages, easy rearing, and short lifespan make it a perfect model organism to study toxicological properties of any new compound. The current study evaluates the toxic effect of a coumarin-based organic fluorescent dye, 7-hydroxy-4-methyl-8-((4-(2-oxo-2H-chromen-3-yl)thiazol-2-ylimino)methyl)-2H-chromen-2-one (CTC), using Drosophila melanogaster as a model organism by studying different behavioral, screening, and staining techniques using Oregon-R flies. For toxicity assessment, one control fly group was compared with various flies that had been subjected to fed CTC dye orally of different concentrations (0.5, 1, 2.5, and 5 µg/mL). The 3rd instar larvae were checked for the larvae crawling assay. The crawling assay demonstrates that the speed and path of the treated larvae are almost equal to the control ones, which signifies the non-neurotoxic property of CTC. Trypan blue assay further suggested that the dye does not cause any major damage to the gut. Phalloidin staining revealed that the actin composition remains unaltered even after the CTC treatment, while the DAPI staining experiment indicates that CTC does not cause any nuclear damage to fly gut cells. However, at a concentration of 5 µg/mL, CTC causes developmental delay. The flies hatched after larval treatment of CTC do not show any structural defects, suggesting clearly that CTC is also nongenotoxic to Drosophila. The current studies propose CTC as a noncytotoxic and nongenotoxic dye to track actin protein in the model organism D. melanogaster.

Synthesis of First Coumarin Fluorescent Dye for Actin Visualization.

Selective fluorescence imaging of actin protein hugely depends on the fluorescently labeled actin-binding domain (ABD). Thus, it is always a challenging task to image the actin protein (in vivo or in vitro) directly with an ABD-free system. To overcome the limitations of actin imaging without an ABD, we have designed a facile and cost-effective red fluorescent coumarin dye 7-hydroxy-4-methyl-8-(4-(2-oxo-2H-chromen-3-yl)thiazol-2-ylimino)methyl-2H-chromen-2-one (CTC) for actin binding. The selective binding of the dye was investigated using the gut and eye of the model organism Drosophila melanogaster and C2C12 and SCC-9 cell lines. Our result suggests two major advantages of CTC over the dyes presently used for imaging actin proteins. First, the dye can bind to actin efficiently without any secondary intermediate. Second, it is much more stable at room temperature and exhibits excellent photostability. To the best of our knowledge, this is the first fluorescent dye that can bind to the actin protein without employing any secondary intermediate/actin-binding domain. These findings could pave the way for many biologists and physicists to successfully employ the CTC dye for imaging and tracking actin proteins by fluorescence microscopy in various in vivo and in vitro systems.

Computational study to evaluate the potency of phytochemicals in Boerhavia diffusa and the impact of point mutation on cyclin-dependent kinase 2-associated protein 1.

A protein's function is closely related to its structural properties. Mutations can affect the functionality of a protein. Different cancer tissues have found disordered expression of the cyclin-dependent kinase 2-associated Protein 1 (CDK2AP1) gene. A protein molecule's conformational flexibility affects its interaction with phytochemicals and their biological partners at various levels. Boerhavia diffusa has been investigated most extensively for its medicinal activities like anticancer properties. It contains many bioactive compounds like Boeravinone A, Boeravinone B, Boeravinone C, Boeravinone D, Boeravinone E, Boeravinone F, Boeravinone G, Boeravinone H, Boeravinone I and Boeravinone J. We have studied to analyse the binding efficacy properties as well as essential dynamic behaviour, free energy landscape of both the native and mutant protein CDK2AP1 with bioactive compounds from Boerhavia diffusa plant extracts through computational approaches by homology modelling, docking and molecular dynamics simulation. From the molecular docking study, we found that. Boeravinone J have best binding affinity (-7.9 kcal/mol) towards the native protein of CDKAP1 compared to others phytochemicals. However, we found the binding energy for H23R and C105R (mutation point) -7.8 and -7.6 kcal/mol, respectively. A single minima energy point (from 100 ns molecular dynamics simulation study) was found in the H23R mutant with Boeravinone J complex suggested that minimum structural changes with less conformational mobility compared C105A mutant model.Communicated by Ramaswamy H. Sarma.

Molecular dynamics simulation perception study of the binding affinity performance for main protease of SARS-CoV-2.

Like common cold and flu, SARC-CoV-2 virus spreads by droplets of sneezes or coughs which virus affects people of various age groups. Today, this virus is almost distributed all over the world. Since binding process plays a crucial role between host and receptor, therefore, we studied the molecules intended toward inhibition process through molecular docking and molecular dynamics simulation process. From the molecular docking study, it is noteworthy that remdesivir shows better binding affinity toward the main protease of SARS-CoV2 compared to other studied drugs. Within studied phytochemicals, carnosic acid shows better binding poses toward main protease of SARS-CoV2 among studied phytochemicals. The amino acid residues GLN110 and PHE294 were almost found in all the studied interactions of drugs and phytochemicals with main protease of SARS-CoV-2. Furthermore, the results show a larger contribution of the Van der Waals energies as compared to others like electrostatic energies suggesting that ligands at the binding pocket are predominantly stabilized by hydrophobic interactions. The conformational change during ligand binding was predicted from Gibbs free energy landscape analysis through molecular dynamics simulation. We observed that, there were two main free energy basins for both docked carnosic acid complex and for docked remdesivir complex, only one main free energy basin was found in the global free energy minimum region.Communicated by Ramaswamy H. Sarma.

Drug resistance reversal potential of multifunctional thieno[3,2-c]pyran via potentiation of antibiotics in MDR P. aeruginosa.

We explored the antibacterial potential (alone and combination) against multidrug resistant (MDR) Pseudomonas aeruginosa isolates KG-P2 using synthesized thieno[3,2-c]pyran-2-ones in combination with different antibiotics. Out of 14 compounds, two compounds (3g and 3l) abridged the MIC of tetracycline (TET) by 16 folds. Compounds was killing the KG-P2 cells, in time dependent manner, lengthened post-antibiotic effect (PAE) of TET and found decreased the mutant prevention concentration (MPC) of TET. In ethidium bromide efflux experiment, two compounds repressed the drug transporter (efflux pumps) which is further supported by molecular docking of these compounds with efflux complex MexAB-OprM. In another study, these compounds inhibited the synthesis of biofilm.

Nanomaterial catalyzed green synthesis of tetrazoles and its derivatives: a review on recent advancements.

Tetrazoles are indispensable nitrogen containing heterocyclic scaffolds that offer a broad spectrum of applications in various domains such as medicinal chemistry, high energy material science, biochemistry, pharmacology etc. Owing to their useful applications, a wide range of catalysts have been explored for green synthesis of tetrazole derivatives. In recent times, nanomaterials have been emerged as extremely efficient catalysts for different organic transformations because of their high surface area-to-volume ratio, easy surface modification, simple fabrications, easy recovery and reusability. In this article, we have presented an overview of utilization of various nano-catalysts, nanocomposites and other solid-supported nanomaterials as an efficient environmental benign catalytic system for green synthesis of tetrazoles and derivatives. This review will provide an exclusive emphasis on boehmite, magnetic, copper, carbon, MCM-41, and composite based nanomaterials that have been developed since the year 2010 for the synthesis of tetrazole derivatives. In addition, we have briefly discussed the fabrication, functionalization and characterization of some novel nanomaterials and their advantages in the synthesis of tetrazole and its derivatives along with the reaction mechanism that involves synthesis of tetrazole derivatives via nanomaterials catalysed reactions.

Fluorometric sensing of hydroxylamine in an aqueous medium utilizing a diphenyl imidazole-based probe.

The detection of hydroxylamine in an aqueous medium is challenging due to its very similar chemical reactivity to its nearest competitors such as hydrazine hydrate and primary amines. Moreover, the detection of hydroxylamine at neutral pH adds further complexity to the sensing phenomenon due to its poor reactivity in a neutral aqueous medium. In this work, we have presented a diphenyl imidazole benzaldehyde (DIB) probe which demonstrates the detection of hydroxylamine (HA) in micromolar concentrations with high selectivity in 5% DMSO phosphate buffer solution at pH 7.4 via a fluorescence "turn-on" signal. The interaction of hydroxylamine with the probe has been comprehensively studied by using fluorescence spectroscopy, proton NMR, FTIR, ESI-mass spectrometry and DLS measurements. The experimental results were further corroborated with the DFT studies. These results could pave the way toward the development of molecular indicators for hydroxylamine in chemical and biological platforms.

Butterfly pea (Clitoria ternatea) extract as a green analytical tool for selective colorimetric detection of bisulphate (HSO4-) ion in aqueous medium.

The blue color of butterfly pea (Clitoria ternatea) was extracted by Milli-Q water and evaluated for selective detection of bisulphate (HSO4-) ions. The stability of the Clitoria ternatea extract was established by UV-visible and fluorescence techniques. The blue water extract from Clitoria ternatea selectively recognizes HSO4- ions over various anions via a distinct visual color change from blue to purple with a significant hypsochromic shift of 68 nm in the UV-visible absorption spectra. Thus Clitoria ternatea extract provides a selective real time colorimetric monitoring of HSO4- ions which would pave the way for the development of low cost green analytical tool. This type of detection technique enhances the environmental and economic benefits and can emerge as an alternative form of synthetic chelating sensors.

Through bond energy transfer (TBET)-operated fluoride ion sensing via spirolactam ring opening of a coumarin-fluorescein bichromophoric dyad.

The detection of fluoride ions in a competitive environment often poses several challenges. In this work, we have designed and synthesized a coumarin functionalized fluorescein dyad (R3) which represents an ideal through bond energy transfer (TBET) fluorophore with the coumarin unit as donor and fluorescein unit as acceptor. The bichromophoric dyad demonstrates the detection of fluoride ions in the parts per billion (ppb) concentration level (22.8 ppb) with high selectivity via a TBET emission signal at 548 nm with a diagnostic bright yellow colour fluorescence output. Based on UV-visible, fluorescence, 1H NMR and DFT studies, it is shown that the fluoride ion induces the opening of the spirolactam ring of the fluorescein moiety and provides a π-conjugation link between the donor and acceptor units enabling a TBET phenomenon with a larger pseudo-Stokes shift of 172 nm. To the best of our knowledge, this is the first report where the fluoride ion is detected via a TBET signal between the coumarin and fluorescein units in a bichromophoric dyad.

Sequential displacement strategy for selective and highly sensitive detection of Zn2+, Hg2+ and S2- ions: An approach toward a molecular keypad lock.

A thiocarbonohydrazone locked salicylidene based macrocycle ligand L has been synthesized and its ion sensing properties were examined by UV-visible and fluorescence spectroscopy. The macrocycle serves as a highly selective colorimetric sensor for Hg2+ ions while it acts as an excellent fluorescent sensor for Zn2+ ions by exhibiting a green fluorescence at 498 nm even in the presence of interfering ions. A detailed analysis of binding characteristics such as complex stoichiometry, association constant and detection limits of L toward Hg2+ and Zn2+ ions were evaluated by UV-visible and fluorescence experiments which revealed a stronger binding affinity and higher detection limit of L toward the mercury ions. Further, the sequential displacement strategy for the chromofluorogenic detection of Zn2+, Hg2+ and S2- ions by ligand L, has been studied comprehensively. Finally, the ion-responsive fluorescence output signal of L were employed to design a molecular keypad lock which could be accessible by two users having two different set of chemical passwords (inputs) through distinguishable optical trajectories.

Fluorescence-based ion sensing in lipid membranes: a simple method of sensing in aqueous medium with enhanced efficiency.

Detection of ions in chemical, biological and environmental samples has gathered tremendous momentum considering the beneficial as well as adverse effects of the ions. Generally, most of the ions are beneficial up to an optimum concentration, beyond which they are toxic to human health. However, most of the fluorescence-based ion sensors are only active in non-aqueous solution because of the low solubility of the sensor molecules in aqueous buffer medium. In the present work, we have demonstrated that encapsulation of an aqueous insoluble thiocarbonohydrazone-locked salicylidene-based macrocyclic ligand in 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) membranes allows the selective detection of Zn2+ in aqueous medium with approximately 3-fold enhanced efficiency compared to its efficiency in DMSO medium. We have further modulated the charge of the membrane surface by adding various concentrations of a negatively charged lipid, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol (POPG), and showed that negative surface charge further enhances the Zn2+ sensing efficiency up to approximately 6-fold. This strategy opens up a new avenue of utilizing organic sensors to detect vital ions in aqueous medium.

Synthesis of 1-amino-2-aroyl/acetylnaphthalenes through a base mediated one pot inter and intramolecular C-C bond formation strategy.

A new precursor 2-(1-cyano-2,2-bis(methylthio)vinyl)benzonitrile has been synthesized by the reaction of 2-cyanomethylbenzonitrile, carbon disulfide and methyl iodide under basic conditions. The reaction of 2-(1-cyano-2,2-bis(methylthio)vinyl)benzonitrile with various functionalized aryl/heteroaryl methyl ketones or acetone under basic conditions afforded 4-amino-3-aroyl/heteroaroyl/acetyl-2-methylsulfanylnaphthalene-1-carbonitriles in good yields through a (5C + 1C) annulation strategy; this involves sequential intermolecular, followed by intramolecular, C-C bond formation reactions. The structure of the product was confirmed by single crystal X-ray crystallography.

Microwave assisted base dependent regioselective synthesis of partially reduced chromenes, isochromenes and phenanthrenes.

We have reported a microwave assisted base directed regioselective synthesis of partially reduced chromenes, isochromenes and phenanthrenes. Functionalized 4-(piperidin-1-yl)-5,6-dihydro-2H-benzo[h]-chromen-2-one-3-carbonitriles have been used as precursors, which on reaction with functionalized acetophenones in the presence of KOH in DMF under microwave irradiation yield (Z)-2-(2-aryl-5,6-dihydro-4H-benzo[f]isochromen-4-ylidene)acetonitriles. The use of NaH in DMF provides 3-aryl-1-(piperidin-1-yl)-9,10-dihydro phenanthrene-2-carbonitriles in excellent yield regioselectively. The use of cyclohexanone as a nucleophile source yields (Z)-2-(3,4,7,8-tetrahydro-1H-naphtho[2,1-c]chromen-6(2H)-ylidene)acetonitriles. The structure and geometry of isochromene have been proved without any ambiguity by single crystal X-ray diffraction.

Molecular capsules derived from resorcin[4]arenes by metal-coordination.

A short introduction to the fundamental features and recent developments of supramolecular chemistry is presented besides defining scope and limitation of this review article. A brief overview about calix[n]arenes and especially resorcin[4]arenes and their conformationally rigid cavitands is given. Selected examples are presented to demonstrate the dependence of self-assembly of cavitands exhibiting different flexibility either due to their basic macrocycle or due to flexible receptor units commonly located at the o,o'-position of the resorcinarene ring. In addition, the process of self-assembly is also controlled by metal coordination geometry as shown by one example. The receptor units may also be connected at the methylene group of the cavitand as shown by one example. Examples of supramolecular architectures are presented utilizing the special features of 2,2':6',2″-terpyridine (terpy) metal-binding ligand. The synthesis and characterization of a metallo-supramolecular Zn-coordination cage with a diameter of 4-5 nm based on a cavitand-terpy building block is presented in detail.