Base dependent pyrrolidine ring pucker in aep-PNA monomers: NMR and PSEUROT analysis

The aep-PNA is a chiral and cyclic PNA analogue, which has a stronger and base dependent binding affinity with complementary DNA. To understand the base dependent properties at monomer level, the structural studies of aep-PNA-(T/C/A) monomers have been carried out focussing on the conformational analysis of pyrrolidine ring pucker in aep-PNA by ¹H NMR and the coupling constant data fitted into PSEUROT software. The results indicate that the type of pyrrolidine pucker depends on the electronic nature of substituent, implying the effect of pyrimidine or purine substituents in determining the ring pucker in monomers. This may consequently influence the aep-PNA oligomer conformation. Since pyrrolidine nucleic acids have emerged as an important class of PNA analogues, present results may have importance for their future development.     

Photoactivatable V-Shaped Bifunctional Quinone Methide Precursors as a New Class of Selective G-quadruplex Alkylating Agents

Combining the selectivity of G-quadruplex (G4) ligands with the spatial and temporal control of photochemistry is an emerging strategy to elucidate the biological relevance of these structures. In this work, we developed six novel V-shaped G4 ligands that can, upon irradiation, form stable covalent adducts with G4 structures via the reactive intermediate, quinone methide (QM). We thoroughly investigated the photochemical properties of the ligands and their ability to generate QMs. Subsequently, we analyzed their specificity for various topologies of G4 and discovered a preferential binding towards the human telomeric sequence. Finally, we tested the ligand ability to act as photochemical alkylating agents, identifying the covalent adducts with G4 structures. This work introduces a novel molecular tool in the chemical biology toolkit for G4s.     

Brassinin inhibits proliferation and induces cell cycle arrest and apoptosis in nasopharyngeal cancer C666-1 cells

BackgroundNasopharyngeal cancer is a tumor that occurs in the mucous epithelium of the nasopharynx. Due to its rapid growth and early metastatic nature, the successful treatment of nasopharyngeal cancer is highly challenging.ObjectiveHere, we intended to assess the in vitro anticancer property of brassinin against the nasopharyngeal cancer C666-1 cells.MethodologyThe in vitro free radical scavenging property of the brassinin was assessed by various free radical scavenging activities such as FRAP, DPPH, chemiluminescence (CL), and ORAC assays. The cytotoxic level of the brassinin (1–50 µM) against the nasopharyngeal cancer C666-1 cells and normal Vero cells were assessed by the MTT cytotoxicity assay. The levels of TBARS, GSH, and the SOD activity was assessed using kits. The level of ROS generation, MMP, and apoptosis were investigated by the respective fluorescent staining techniques. The flow cytometry analysis was done to scrutinize the cell cycle arrest. The Bax/Bcl-2 level and caspase activities were examined using respective kits.ResultsThe brassinin treatment effectively scavenged the free radicals, which are assessed by the FRAP, DPPH, chemiluminescence (CL), and ORAC assays. The proliferation of brassinin treated C666-1 cells were decreased remarkably, while the same concentration of brassinin did not disturbed the Vero cell viability. The 30 µM of brassinin effectively increased the ROS production, depleted the MMP, and stimulated the apoptosis in the C666-1 cells. The brassinin increased the TBARS and depleted the GSH and SOD in the C666-1 cells. The flow cytometry analysis revealed that the brassinin administration improved the G0/G1 ratio and decreased the proportion of cells with ‘S’ and ‘G2/M’ phase. The Bax, caspase-3 and ?9 were elevated and Bcl-2 level was decreased in the brassinin administered C666-1 cells.ConclusionOur findings discovered that the brassinin has the capacity to prevent the proliferation and stimulate the apoptotic cell death C666‐1 cells via blocking cell cycle and increasing oxidative stress and apoptotic markers. Hence, it can be a talented therapeutic agent to treat the nasopharyngeal cancer in the future.     

Anticancer Effects and Molecular Action of 7-α-Hydroxyfrullanolide in G2/M-Phase Arrest and Apoptosis in Triple Negative Breast Cancer Cells

Triple negative breast cancer (TNBC) is a breast cancer subtype characterized by the absence of estrogen receptor, progesterone receptor and human epidermal growth factor receptor 2 expression. TNBC cells respond poorly to targeted chemotherapies currently in use and the mortality rate of TNBC remains high. Therefore, it is necessary to identify new chemotherapeutic agents for TNBC. In this study, the anti-cancer effects of 7-α-hydroxyfrullanolide (7HF), derived from Grangea maderaspatana, on MCF-7, MDA-MB-231 and MDA-MB-468 breast cancer cells were assessed using MTT assay. The mode of action of 7HF in TNBC cells treated with 6, 12 and 24 µM of 7HF was determined by flow cytometry and propidium iodide (PI) staining for cell cycle analysis and annexin V/fluorescein isothiocyanate + PI staining for detecting apoptosis. The molecular mechanism of action of 7HF in TNBC cells was investigated by evaluating protein expression using proteomic techniques and western blotting. Subsequently, 7HF exhibited the strongest anti-TNBC activity toward MDA-MB-468 cells and a concomitantly weak toxicity toward normal breast cells. The molecular mechanism of action of low-dose 7HF in TNBC cells primarily involved G2/M-phase arrest through upregulation of the expression of Bub3, cyclin B1, phosphorylated Cdk1 (Tyr 15) and p53-independent p21. Contrastingly, the upregulation of PP2A-A subunit expression may have modulated the suppression of various cell survival proteins such as p-Akt (Ser 473), FoxO3a and β-catenin. The concurrent apoptotic effect of 7HF on the treated cells was mediated via both intrinsic and extrinsic modes through the upregulation of Bax and active cleaved caspase-7–9 expression and downregulation of Bcl-2 and full-length caspase-7–9 expression. Notably, the proteomic approach revealed the upregulation of the expression of pivotal protein clusters associated with G1/S-phase arrest, G2/M-phase transition and apoptosis. Thus, 7HF exhibits promising anti-TNBC activity and at a low dose, it modulates signal transduction associated with G2/M-phase arrest and apoptosis.     

Determination of cerium in rare earth ores by fluorescence quenching of rhodamine 6G

A fluorescence quenching method has been developed to determine cerium with rhodamine 6G. The method is based on the oxidation of rhodamine 6G by cerium(IV) in sulfuric acid solution. The linear calibration range is 4.0 × 10^–7 -1.6 × 10^–6mol/L. The detection limit is 1.0 × 10^–7 mol/L. The relative standard deviation was 1.0% (n = 5). The method has been used to determine cerium in rare earth ores, with satisfactory results. The method offers the advantages of simplisity, sensitivity and selectivity.     

Stabilization ofEscherichia coli penicillin G acylase by polyethylene glycols against thermal inactivation

The effects of five polyethylene glycol (PEG) compounds of different molecular weight on the thermal stability of penicillin G acylase (PGA) obtained from a mutant ofEscherichia coli ATCC 11105 have been investigated. The molecular weights of PEG compounds were 400, 4000, 6000, 10,000, and 15,000. The thermal inactivation mechanisms of both native and PEG-containing PGA were considered to obey first order inactivation kinetics during prolonged heat treatments. Optimal concentrations of PEGs at molecular weights of 400,4000, 6000,10,000, and 15,000 were found to be 250,150,150,100, and 50 mM, respectively. The greatest enhancement of thermostability was observed with PEG 4000 and PEG 6000, as a nearly 20-fold increase above 50°C. PGA showed almost the same temperature activity profile and optimal temperature values both in the presence and absence of PEG. The addition of PEGs did not cause any change in the optimal temperature value of PGA, but the parametersV _m ,K _m , the activation energy, and thek _cat values of enzyme were markedly decreased because of the mixed inhibition by PEG compounds. The type of inhibition was found to be hyperbolic uncompetitive.     

Spectrophotometric estimation of ketotifen fumarate in pharmaceutical formulations

Four simple and sensitive spectrophotometric methods (A–D) for the determination of Ketotifen fumarate in bulk samples and pharmaceutical formulations are described. They are based on the formation of coloured species by the coupling of the diazotised sulphanilamide with the drug (method A, _max 520 nm) or by oxidizing it with excessN-bromo-succinimide and determining the consumed NBS with decrease in colour intensity of celestine blue (method B: _max 540 nm) or by the reduction of Folin-Ciocalteau reagent (method C: _max 720 nm) or by the formation of a chloroform-soluble, coloured ionassociation complex between the drug and Azocarmine G at pH 1.5 (method D: _max 540 nm). Regression analysis of Beer-Lambert plots showed good correlations in the concentration ranges 1–10, 2–12, 4–28 and 2.5–25 g/ml for methods A–D, respectively. The validity of the proposed methods was tested by analysing pharmaceutical formulations containing KTF: the relative standard deviations were within ±1.0%. Recoveries were 98.9–100.2%.     

Assessing G4-Binding Ligands In Vitro and in Cellulo Using Dimeric Carbocyanine Dye Displacement Assay

G-quadruplexes (G4) are the most actively studied non-canonical secondary structures formed by contiguous repeats of guanines in DNA or RNA strands. Small molecule mediated targeting of G-quadruplexes has emerged as an attractive tool for visualization and stabilization of these structures inside the cell. Limited number of DNA and RNA G4-selective assays have been reported for primary ligand screening. A combination of fluorescence spectroscopy, AFM, CD, PAGE, and confocal microscopy have been used to assess a dimeric carbocyanine dye B6,5 for screening G4-binding ligands in vitro and in cellulo. The dye B6,5 interacts with physiologically relevant DNA and RNA G4 structures, resulting in fluorescence enhancement of the molecule as an in vitro readout for G4 selectivity. Interaction of the dye with G4 is accompanied by quadruplex stabilization that extends its use in primary screening of G4 specific ligands. The molecule is cell permeable and enables visualization of quadruplex dominated cellular regions of nucleoli using confocal microscopy. The dye is displaced by quarfloxin in live cells. The dye B6,5 shows remarkable duplex to quadruplex selectivity in vitro along with ligand-like stabilization of DNA G4 structures. Cell permeability and response to RNA G4 structures project the dye with interesting theranostic potential. Our results validate that B6,5 can serve the dual purpose of visualization of DNA and RNA G4 structures and screening of G4 specific ligands, and adds to the limited number of probes with such potential.