Synthesis and Spectroscopic Studies of N,N’-dialkyl Derivatives of Antisymmetrical 2H,5H-Dihydropyrrolo[3,4-c]pyrrole-1,4-diones

2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione derivatives (DPP) are chemically stable, fluorescent molecules, known as High Performance Pigments. Preparation of the soluble derivatives of DPPs provides great advantage in designing the optic sensor for new and existing applications and overcoming aggregation problems in solid matrices. For this purpose, the synthesis of antisymmetric DPPs and the formation of new organic dyes through N,N’-dialkylation and their spectroscopic studies have been carried out both in solutions and in solid phase.     

Cholesterol effects on vesicle pools in chromaffin cells revealed by carbon-fiber microelectrode amperometry

Cell–cell communication is often achieved via granular exocytosis, as in neurons during synaptic transmission or neuroendocrine cells during blood hormone control. Owing to its critical role in membrane properties and SNARE function, cholesterol is expected to play an important role in the highly conserved process of exocytosis. In this work, membrane cholesterol concentration is systematically varied in primary culture mouse chromaffin cells, and the change in secretion behavior of distinct vesicle pools as well as pool recovery following stimulation is measured using carbon-fiber microelectrode amperometry. Amperometric traces obtained from activation of the younger readily releasable and slowly releasable pool (RRP/SRP) vesicles at depleted cholesterol levels showed fewer sustained fusion pore features (6.1 ± 1.1% of spikes compared with 11.2 ± 1.0% for control), revealing that cholesterol content influences fusion pore formation and stability during exocytosis. Moreover, subsequent stimulation of RRP/SRP vesicles showed that cellular cholesterol level influences both the quantal recovery and kinetics of the later release events. Finally, diverging effects of cholesterol on RRP and the older reserve pool vesicle release suggest two different mechanisms for the release of these two vesicular pools.     

Determination of pK a of benzoic acid- and p-aminobenzoic acid-modified platinum surfaces by electrochemical and contact angle measurements

Acidity constant values of benzoic acid (BA)-modified platinum electrode (Pt-BA) and p-aminobenzoic acid (pABA)-modified platinum electrode (Pt-NHBA) surfaces were determined using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and contact angle measurements (CAM). Diazonium tetrafluoroborate salt reduction and pABA oxidation reactions were used to prepare (Pt-BA) and (Pt-NHBA) surfaces, respectively. Both surfaces exhibited pH dependence with [Fe(CN)₆]^3?/4? redox probe solutions at different pH; this allowed us to estimate the surface pK _a values. Acidity constants for Pt-BA surface were found to be pK _a (3.09 ± 0.25), (4.89 ± 0.11), and (3.91 ± 0.54) by CV, EIS, and CAM techniques, respectively, while the values for Pt-NHBA surface were pK _a (3.16 ± 0.45), (4.24 ± 0.40), and (5.64 ± 0.12). The Pt-BA surface pK _a values were lower in CV and CAM measurements relative to the bulk solution of BA, while a higher value was observed in EIS for Pt-BA surface. The pK _a values determined for Pt-NHBA surface via both CV and EIS were lower than the bulk value; however, the result obtained from CAM was one unit higher than pK _a of bulk pABA.     

Determination of the effect of Quercetinon oxidant- antioxidant parameters in the blood and liver tissues of rats given sodium fluoride experimentally

AimThe purpose of the study is to research the effect of quercetin, which has a good antioxidant characteristic in rats exposed to sodium fluoride (NaF) toxication, on oxidant and antioxidant activity in liver tissue and erythrocyte.Material and method40 Swiss albino male rats with a weight of approximately 20–25 gr were used in the study. The rats were separated into 4 equal groups (n = 10). The first group, the control group, was given normal drinking water; the second group was given 12 mg/kg/day NaF; the third group was given 40 mg/kg/day quercetin; the fourth group was given 12 mg/kg/day NaF+40 mg/kg/day quercetin orally for 30 days. As a result of the experiment, plasma AST and ALT activities were found. Total oxidant capacity (TOC) and total antioxidant capacity (TAC) analyses were made in liver tissue and erythrocyte hemogenisate. Histopathological analyses of the liver tissue were conducted.ResultsNo changes were found in plasma ALT activities between groups. Increases were found in AST activity of all groups. While erythrocyte TAC level was found to increase in fluorine and fluorine + quercetin group when compared with the control group, erythrocyte TOC level was found to increase in all groups when compared with the control group. No significant change was found in TOC and TAC levels in the liver tissue. In liver tissue histopathology, while hydropic degeneration and cellular necrosis were found in vena centralis area in fluorine group, hydropic degeneration was found in heptocytes in centrilobular area in the quercetin group. In the fourth group, hydropic degeneration and centrilobular necrosis were more severe. It was found that in rats which are given NaF experimentally, fluorine and quercetin caused histopathological degenerations in the liver tissue during this time.ConclusionWhile no changes were found in TOC and TAC levels of liver tissue, antioxidant capacity was found to be stimulated in fluorine groups in erythrocyte.     

Bioanalytical tools for single-cell study of exocytosis

Regulated exocytosis is a fundamental biological process used to deliver chemical messengers for cell-cell communication via membrane fusion and content secretion. A plethora of cell types employ this chemical-based communication to achieve crucial functions in many biological systems. Neurons in the brain and platelets in the circulatory system are representative examples utilizing exocytosis for neurotransmission and blood clotting. Single-cell studies of regulated exocytosis in the past several decades have greatly expanded our knowledge of this critical process, from vesicle/granule transport and docking at the early stages of exocytosis to membrane fusion and to eventual chemical messenger secretion. Herein, four main approaches that have been widely used to study single-cell exocytosis will be highlighted, including total internal reflection fluorescence microscopy, capillary electrophoresis, single-cell mass spectrometry, and microelectrochemistry. These techniques are arranged in the order following the route of a vesicle/granule destined for secretion. Within each section, the basic principles and experimental strategies are reviewed and representative examples are given revealing critical spatial, temporal, and chemical information of a secretory vesicle/granule at different stages of its lifetime. Lastly, an analytical chemist’s perspective on potential future developments in this exciting field is discussed.     

Iron(III) selective fluorescence probe based on perylene tetracarboxylic diimide

Responses of organic fluorophore, perylenediimide derivative N,N′-di[3-[2-(3-thienyl)ethyl]phenyl]perylene-3,4,9,10-bis-(dicarboxyimide) (PDI1) was investigated in polymer matrix of polyvinyl chloride (PVC) by emission spectrometry. Its response to Fe(III) ions was evaluated in terms of the effect of pH. The properties of time dependent response, reversibility, limit of detection, linear concentration range for the metal ion and repeatability characteristics of the sensing element also have been studied. The offered sensor exhibited remarkable fluorescence intensity quenching at pH 6.0 in the concentration range of 1 × 10^?6 to 2.5 × 10^?3 M Fe(III) ions. The reproducibility of the sensor membrane was investigated by alternately changing the solution between 1 × 10^?4 M Fe(III) in Na₂HPO₄ (4 × 10^?2 M) and NaH₂PO₄ buffer (2 × 10^?3 M).     

Ligandless cloud point extraction of Cr(III), Pb(II), Cu(II), Ni(II), Bi(III), and Cd(II) ions in environmental samples with Tween 80 and flame atomic absorption spectrometric determination

A cloud point extraction (CPE) procedure has been developed for the determination trace amounts of Cr(III), Pb(II), Cu(II), Ni(II), Bi(III), and Cd(II) ions by using flame atomic absorption spectrometry. The proposed cloud point extraction method was based on cloud point extraction of analyte metal ions without ligand using Tween 80 as surfactant. The surfactant-rich phase was dissolved with 1.0 mL 1.0 mol L⁻¹ HNO₃ in methanol to decrease the viscosity. The analytical parameters were investigated such as pH, surfactant concentration, incubation temperature, and sample volume, etc. Accuracy of method was checked analysis by reference material and spiked samples. Developed method was applied to several matrices such as water, food and pharmaceutical samples. The detection limits of proposed method were calculated 2.8, 7.2, 0.4, 1.1, 0.8 and 1.7 μg L⁻¹ for Cr(III), Pb(II), Cu(II), Ni(II), Bi(III), and Cd(II), respectively.     

Epithelial-to-Mesenchymal Transition Is Not a Major Modulating Factor in the Cytotoxic Response to Natural Products in Cancer Cell Lines

Numerous natural products exhibit antiproliferative activity against cancer cells by modulating various biological pathways. In this study, we investigated the potential use of eight natural compounds (apigenin, curcumin, epigallocatechin gallate, fisetin, forskolin, procyanidin B2, resveratrol, urolithin A) and two repurposed agents (fulvestrant and metformin) as chemotherapy enhancers and mesenchymal-to-epithelial (MET) inducers of cancer cells. Screening of these compounds in various colon, breast, and pancreatic cancer cell lines revealed anti-cancer activity for all compounds, with curcumin being the most effective among these in all cell lines. Although some of the natural products were able to induce MET in some cancer cell lines, the MET induction was not related to increased synergy with either 5-FU, irinotecan, gemcitabine, or gefitinib. When synergy was observed, for example with curcumin and irinotecan, this was unrelated to MET induction, as assessed by changes in E-cadherin and vimentin expression. Our results show that MET induction is compound and cell line specific, and that MET is not necessarily related to enhanced chemosensitivity.