Hydrazine sensors development based on a glassy carbon electrode modified with a nanostructured TiO2 films by electrochemical approach

Microchimica Acta - The authors describe a selective hydrazine sensor that is based on the use of a film of TiO2 nanoparticles faceted predominantly at the 101 and 001 sides. The hydrazine (Hyd)...     

Charge-Transfer Reaction of Chloranilic Acid with Crizotinib: Spectrophotometric Study,Computational Modeling and Use in Development of Microwell Assay for Crizotinib

The reaction of chloranilic acid (CA) with crizotinib (CZT); a novel drug used for treatment of non-small cell lung cancer) was investigated in different solvents of varying dielectric constants and polarity indices. The reaction resulted in the formation of a violet-colored product. Spectrophotometric investigations confirmed that the reaction proceeded through CT complex formation. The molar absorptivity of the CT complex produced was found to be linearly correlated with the dielectric constant and polarity index of the solvent. The association constant of the CA–CZT CT complex and the stoichiometric ratio of CA:CZT were determined. Computational molecular modeling for the CT complex between CA and CZT was conducted, the sites of interaction on CZT molecule were determined, and the mechanism of the reaction was postulated. The reaction was employed as a basis for the development of a novel 96-microwell assay for CZT. In this assay, the absorbances of the CA–CZT CT complex solutions were measured by a microwell-plate absorbance reader. The CZT limits of detection and quantitation are 8.8 and 26.4 μg·mL^?1, respectively. The assay was successfully applied to the analysis of CZT in its bulk form and capsules with good accuracy and precision. The assay described herein has great practical value as it has high throughput and consumes minimum volume of organic solvent, thus it reduces the exposures of the analysts to the toxic effects of organic solvents, and significantly reduces the analysis cost.     

Salt effects on reactivities of low-spin iron(II) complexes of diazabutadiene and Schiff base ligands

Salt effects on reactivity are reported for base hydrolysis of tris-ligand-iron(II) complexes of several diazabutadiene and Schiff base ligands in aqueous solutions of alkali metal halides and of tetraalkylammonium bromides. The observed patterns vary markedly with ligand nature, the trend paralleling ligand hydrophilicity. These patterns of salt effects on reactivity are compared with those for a variety of other inorganic substitution reactions.     

C60 fullerene binding to DNA

Fullerenes have attracted considerable attention in various areas of science and technology. Owing to their exceptional physical, chemical, and biological properties, they have many applications, particularly in cosmetic and medical products. Using the Lennard-Jones 6-12 potential function and the continuum approximation, which assumes that intermolecular interactions can be approximated by average atomic surface densities, we determine the binding energies of a C₆₀ fullerene with respect to both single-strand and double-strand DNA molecules. We assume that all configurations are in a vacuum and that the C₆₀ fullerene is initially at rest. Double integrals are performed to determine the interaction energy of the system. We find that the C₆₀ fullerene binds to the double-strand DNA molecule, at either the major or minor grooves, with binding energies of ?4.7 eV or ?2.3 eV, respectively, and that the C₆₀ molecule binds to the single-strand DNA molecule with a binding energy of ?1.6 eV. Our results suggest that the C₆₀ molecule is most likely to be linked to the major groove of the dsDNA molecule.     

Kinetics of base hydrolysis of tris-(1,10-phenanthroline)iron(II) and of solvolysis of cis-dichlorobis(1,2-ethanediamine)cobalt(III) in water + diol mixtures

Rate constants for base hydrolysis of the tris-(1,10-phenanthroline)iron(II) cation and for solvolysis of the cis-dichlorobis(1,2-ethanediamine)cobalt(III) cation have been measured in binary aqueous mixtures containing 1,2-ethanediol, 1,2- or 1,4-butanediol, 1,2- or 1,6-hexanediol, 1-propanol, or t-butyl alcohol, at 298.2 K. Kinetics of base hydrolysis of the cobalt(III) complex have also been monitored in methanol-water and ethanol-water mixtures, again at 298.2 K. The observed reactivity trends are discussed in terms of the hydrophilic and hydrophobic properties of the respective diols. The dominant factor determining reactivity is hydration of the attacking hydroxide or leaving chloride, as is evidenced by the close correspondence between rate constants and transfer chemical potentials for these anions. The role of hydration has also been probed through the determination of activation volumes for these two reactions in 60% 1,4-butanediol. © 1993 John Wiley & Sons, Inc.     

Reactivity and solvatochromism of pentacyanoferrate(II) complexes in diol–water mixtures

Rate constants are reported for substitution at the pentacyanoferrate(II) ions [Fe(CN)5L]3−, where L=3,5-dimethylpyridine or 3-cyanopyridine, in binary aqueous mixed solvents containing up to 60vol% 1,2-ethanediol, 1,2-butanediol, methanol or ethanol. Trends for diol-containing mixtures are compared with those for monohydroxylic alcohols, and the reactivity pattern for these complexes is compared with those established earlier for base hydrolysis of tris(1,10-phenanthroline)iron(II) and for the aquation of cis-dichloro-bis- (1,2-ethanediamine)cobalt(III). The solvatochromic behaviour of several pentacyanoferrate(II) ions has been established in binary aqueous mixtures containing 1,2-ethanediol, 1,2-butanediol, 1,4-butanediol and 1,2-pentanediol. A correlation between reactivity and solvatochromism is presented. This revised version was published online in June 2006 with corrections to the Cover Date.     

Dynamic spatial and structural organization in artificial cells regulates signal processing by protein scaffolding

Structural and spatial organization are fundamental properties of biological systems that allow cells to regulate a wide range of biochemical processes. This organization is often transient and governed by external cues that initiate dynamic self-assembly processes. The construction of synthetic cell-like materials with similar properties requires the hierarchical and reversible organization of selected functional components on molecular scaffolds to dynamically regulate signaling pathways. The realization of such transient molecular programs in synthetic cells, however, remains underexplored due to the associated complexity of such hierarchical platforms. In this contribution, we effectuate dynamic spatial organization of effector protein subunits in a synthetic biomimetic compartment, a giant unilamellar vesicle (GUV), by associating in a reversible manner two fragments of a split luciferase to the membrane. This induces their structural dimerization, which consequently leads to the activation of enzymatic signaling. Importantly, such organization and activation are dynamic processes, and can be autonomously regulated – thus opening up avenues toward continuous spatiotemporal control over supramolecular organization and signaling in an artificial cell.

Engineered artificial cells respond to environmental cues through a pre-programmed enzymatic machinery that induces spatio-structural organization and activation of effector proteins at the lipid membrane.     

Holospiniferoside: A New Antitumor Cerebroside from The Red Sea Cucumber Holothuria spinifera: In Vitro and In Silico Studies

Chemical investigation of the methanolic extract of the Red Sea cucumber Holothuria spinifera led to the isolation of a new cerebroside, holospiniferoside (1), together with thymidine (2), methyl-α-d-glucopyranoside (3), a new triacylglycerol (4), and cholesterol (5). Their chemical structures were established by NMR and mass spectrometric analysis, including gas chromatography–mass spectrometry (GC–MS) and high-resolution mass spectrometry (HRMS). All the isolated compounds are reported in this species for the first time. Moreover, compound 1 exhibited promising in vitro antiproliferative effect on the human breast cancer cell line (MCF-7) with IC₅₀ of 20.6 µM compared to the IC₅₀ of 15.3 µM for the drug cisplatin. To predict the possible mechanism underlying the cytotoxicity of compound 1, a docking study was performed to elucidate its binding interactions with the active site of the protein Mdm2–p53. Compound 1 displayed an apoptotic activity via strong interaction with the active site of the target protein. This study highlights the importance of marine natural products in the design of new anticancer agents.     

Electrical properties of CuTlSe2 in the liquid state

The electrical conductivity and thermoelectric power of CuTlSe₂ have been investigated as a function of temperature up to 230 °C above its melting point. In the liquid state the experimental data are analyzed in terms of a model developed for the density of states and electrical transport in solid amorphous semiconductors (Mott, 1970). Positive thermoelectric power suggests a large predominance of holes in electrical conduction. It appears that the conduction is due to holes in extended states near the band edge. It is found that the energy gap has a large temperature coefficient =5.5×10^–4eV/K.