Fluorescence based metabisulfite sensing: New aspects of ion sensing by a styryl benzothiazolium dye and understanding nitrite interference.

Detection of specific ions using fluorescent probes has relevance in several areas of therapeutics development and environmental science. Here, we provide new perspectives to the sensing of a styryl benzothiazolium-based fluorescent compound 1 and report that sensing properties are for sulfite ions in general with highest preference for metabisulfite ions (S2O52-) adding to its previously determined role as a bisulfite ion sensor. This probe exhibits its sensing action via an addition reaction in which the styryl double bond gets reduced. The interference studies highlighted that the sequence of addition of nitrite and metabisulfite has a bearing on the overall interference outcome. Spectroscopic studies revealed that the order of preferential sensing of sulfites and sulfide ion is S2O52- > HSO3- > SO32- > S2-. Although this probe displays robust sensing on its own through fluorescence quenching, its fluorescence emission can be enhanced at much lower concentrations in the presence of a G-quadruplex DNA without compromising the outcome of the sensing.

Bacterial rRNA A-site recognition by DAPI: Signatures of intercalative binding.

The bacterial A-site RNA is one of the key targets towards the development of new antibacterials including new treatment options for tuberculosis. Using DAPI as a prototype, we have explored the potential of bisamidines as a potential chemical motif for bacterial A-site recognition. We have demonstrated that the binding of DAPI shows a concentration-dependent thermal stabilization of the bacterial A-site RNA (ΔTm = 9.9 °C). The binding, however, does not show pH-dependent changes upon lowering of pH. Both UV-vis and CD experiments show that the DAPI binding involves base stacking with the RNA bases in a manner that is analogous to intercalation. Scatchard analysis of the UV-vis titration data revealed a micromolar affinity of the DAPI to the bacterial rRNA A-Site (Ka = 1.14 × 106 M-1) which was corroborated by the FID-based relative binding affinity comparison with aminoglycosides. The molecular docking studies showed binding poses consistent with polar and stacking interactions with the RNA. These studies highlight the role of amidines in bacterial A-site recognition and the need for the development of their structural analogs towards the making of aminoglycoside mimics.

New Approaches in Sensing and Targeting Bacterial rRNA A-site.

New chemical agents that could combat increasing antibiotic resistance are urgently needed. In this mini-review, an old but highly relevant RNA sequence which is crucial for the continuation of bacterial life-cycle is covered. Some of the most significant advances of the last decade in sensing and targeting the bacterial rRNA A-site: a well-validated binding site of proverbially known aminoglycoside antibiotics are described. Some of the major advances in direct sensing of the bacterial decoding side (A-site) are described and also new fluorescent molecules that are capable of detecting lead compounds through high-throughput assays by displacement of fluorescent probe molecules are highlighted. Lastly, some of the recently discovered non-aminoglycoside small molecule binders of bacterial rRNA A-site as a new class of molecules that could provide future scaffolds and molecules for developing new antibacterial agents have been discussed.

Design, computational studies, synthesis and biological evaluation of thiazole-based molecules as anticancer agents.

BACKGROUND: Abolition of cancer warrants effective treatment modalities directed towards specific pathways dysregulated in tumor proliferation and survival. The antiapoptotic Bcl-2 proteins are significantly altered in several tumor types which position them as striking targets for therapeutic intervention. Here we designed, computationally evaluated, synthesized, and biologically tested structurally optimized thiazole-based small molecules as anticancer agents. METHODS: The virtually designed 200 molecules were subjected to rigorous docking and in silico ADME-Toxicity studies. Out of this, 23 skeletally diverse thiazole-based molecules which passed pan assay interference compounds (PAINS) filter and were synthetically feasible were synthesized in 3 steps using cheap and readily available reagents. The molecules were in vitro evaluated against Bcl-2-Jurkat, A-431 cancerous cell lines and ARPE-19 cell lines. Molecular Dynamics (MD) simulation studies were performed to analyse conformational changes induced by ligand 32 in Bcl-2. Flow cytometry analysis of compound 32 treated Bcl-2 cells was done to check apoptosis. RESULTS: The molecules exhibited appreciable interactions with Bcl-2 and were having acceptable drug like properties as tested in silico. The multi step synthesis yielded 23 skeletally diverse thiazole-based molecules in up to 80% yield. The molecules simultaneously inhibited Bcl-2 Jurkat cells in vitro without causing detectable toxicity to normal cells (ARPE-19 cells). Among them molecules 32, 50, 53, 57 and 59 showed considerable activities against Bcl-2 Jurkat and A-431cell lines at concentrations ranging from 32-46 µM and 34-52 µM, respectively. The standard doxorubicin exhibited IC50 in Bcl-2 Jurkat and A-431cell lines at 45.87 µM and 42.37 µM, respectively. The molecule 32, almost equipotent in both the cell lines was subjected to molecular dynamics (MD) simulation with Bcl-2 protein (4IEH). It was shown that 32 interacted with protein majorly via hydrophobic interactions and few H-bonding interactions. Fluorescence-activated cell sorting (FACS) analysis established that molecule is dragging cancerous cells towards apoptosis. DISCUSSION AND CONCLUSION: The chemical intuition was checked by computation coupled with biological results confirmed that thiazole-based hits have the potential to be developed downstream into potent and safer leads against antiapoptotic Bcl-2 cells.