A ruthenium(II)-trithiacyclononane curcuminate complex: Synthesis,characterization, DNA-interaction,and cytotoxic activity

The coordination of ruthenium(II) complexes to anionic oxygen-based donors are very rare. This study describes a simple, one-pot method for obtaining [ruthenium(II)(trithiacyclononane)(curcumin)(S-DMSO)]Cl (1) in 37% yield. The structural characterization of complex 1 by elemental analysis, FT-IR, 1-D and 2-D NMR, ESI⁺-MS as well as UV–vis and fluorescence spectroscopies are presented. The DNA-melting temperature (T_m) assay shows that salmon sperm DNA (smDNA) in the presence of complex 1 has a higher melting temperature, with ΔT_m = 7.4 °C, while in the presence of curcumin the melting temperature remains unaltered. The in vitro cytotoxic activities of curcumin and complex 1 were investigated using the tumor human prostate cell line, PC-3, and the healthy cell line, PNT-2. Complex 1 is innocuous toward normal prostate epithelial cells and, whereas curcumin is toxic, with inhibition rates of ca. 35 and 65% at 50 and 80 μM, respectively. On the tumor cell line PC-3, complex 1 did not cause viability changes, whereas curcumin exhibited dose-dependent inhibition, with ca. 73% inhibition at the highest concentration tested, i.e. 80 μM. This study suggests that coordination with the trithiacyclononane ruthenium(II) scaffold stabilizes the photochemical properties of curcumin and strongly changes its biologic activity.     

Chemometric analysis for optimizing derivatization in gas chromatography‐based procedures

This paper focuses on the application of principal component analysis (PCA) to facilitate the optimization of the derivatization of oestrogenic steroids—estrone, 17β‐estradiol, estriol, 17α‐ethinylestradiol and diethylstilbestrol—in order to achieve (1) the complete derivatization of all the hydroxyl groups contained in the structure of the compounds and (2) the greatest effectiveness of this reaction. Six different derivatization reagents were used in this study, whereas 2‐methyl‐anthracene was applied as the internal standard to evaluate the effectiveness of the reactions. The experimental data were subjected to PCA. With PCA, the dimensionality of the original multivariable data set could be reduced and the selection of optimum conditions for derivatization facilitated. The mixture of 99% N,O‐bis(trimethylsilyl)trifluoroacetamide + 1% trimethylchlorosilane and pyridine (1:1, v/v) at 60 °C for 30 min has been established as the most convenient and efficient means of derivatizing the aforementioned oestrogenic steroids and diethylstilbestrol; the N‐methyl‐N‐(trimethylsilyl)trifluoroacetamide + pyridine (1:1, v/v) mixture seems to be a promising alternative. The application of PCA for optimizing the derivatization procedure, proposed for the first time in this study, is particularly useful in the development of multicomponent methods across several chemical classes of compounds. Copyright © 2011 John Wiley & Sons, Ltd.     

Low-density polyethylene in mixtures of hexane and benzene derivates

Preferential sorption, equilibrium swelling degree, and volume of the swollen membrane in systems low-density polyethylene + hexane + aromatic compound (benzene, methylbenzene, or ethylbenzene) were studied using gravimetric and dilatometric methods at the temperature of 25 °C. Aromatic compounds are preferentially sorbed in low-density polyethylene compared to hexane. Experimental volume changes of the membrane were found to be noticeably different from those calculated on the basis of mass sorption data under the assumption of additivity. This difference points to the existence of the interactions between the polymer and the surrounding liquid mixture. The volume swelling degree curves are close to each other in the whole concentration range of the binary liquid mixture (hexane + aromatics) suggesting that the attractive forces between the polymer chains are the deciding factor limiting the volume expansion of the membrane in all three systems to the same extent.     

Fluorescent chemosensors for metal ions based on 3-(2-benzoxazol-5-yl)alanine skeleton

The ability of new chelate ligands, benzoxazol-5-yl-alanine derivatives substituted in position 2 by heteroaromatic substituent, to form complexes with selected metal ions in acetonitrile are studied by means of absorption and steady-state and time-resolved fluorescence spectroscopy. Among the ligands studied, only azaaromatic derivatives form stable complexes with transition metal ions in the ground state. Their absorption bands are bathochromically shifted enabling to use those ligands as ratiometric sensors. The fluorescence of each ligand is quenched by metal ions, however, in the presence of Cd(II) and Zn(II) ions a new red shifted emission band is observed.      

Kinetics of the Reaction of 2-Chloro-quinoxaline with Hydroxide Ion in ACN–H2O and DMSO–H2O Binary Solvent Mixtures

The kinetics of alkaline hydrolysis of 2-chloroquinoxaline (QCl) with hydroxide ion was investigated spectrophotometrically at different percentages of aqueous–organic solvent mixtures with acetonitrile (10–60% v/v) and with dimethylesulphoxide (10–80%) over the temperature range from 25 to 45 °C. The reaction was performed under pseudo first order conditions with respect to 2-chloroquinoxaline (QCl). An increase in the percentage of organic solvent (v/v) has different effects on the reaction rate constants, presumably due to hydrogen bond donor and acceptor differences of the media and other solvatochromic parameters. The data were discussed in terms of the Kamelt-Taft parameter and E _T(30). A nonlinear relation between the logarithm of the rate constant and reciprocal of the dielectric constant suggests the presence of selective solvation by the polar water molecules. Activation parameters ΔH ^#, ΔS ^# and ΔG ^# were determined and discussed.     

Stereoselective synthesis of tetracyclic indolines via gold-catalyzed cascade cyclization reactions

A reliable synthetic route to fused polycyclic indolines is documented by the development of a stereoselective gold catalyzed cascade cyclization of indole propargylic alcohols.     

Nature-inspired cascade catalysis: reaction control through substrate concentration--double vs. quadruple domino reactions

The design of biologically inspired, multi-component cascade reactions enables the targeted synthesis of assorted structurally complex products. Similar to regulation in cells the reaction path is controlled by the substrate concentration and complex enantiopure products with high structural diversity are provided.     

The effect of lipid oxidation on the water permeability of phospholipids bilayers

The effect of lipid oxidation on water permeability of phosphatidylcholine membranes was investigated by means of both scattering stopped flow experiments and atomistic molecular dynamics simulations. Formation of water pores followed by a significant enhancement of water permeability was observed. The molecules of oxidized phospholipids facilitate pore formation and subsequently stabilize water in the membrane interior. A wide range of oxidation ratios, from 15 to 100 mol%, was considered. The degree of oxidation was found to strongly influence the time needed for the opening of a pore. In simulations, the oxidation ratio of 75 mol% was found to be a threshold for spontaneous pore formation in the tens of nanosecond timescale, whereas 15 mol% of oxidation led to significant water permeation in the timescale of seconds. Once a pore was formed, the water permeability was found to be virtually independent of the oxidation ratio.