DNA binding and antitumor activities of zinc(II) complexes with some S-alkenyl derivatives of thiosalicylic acid

Transition Metal Chemistry - Two zinc(II) complexes with S-alkenyl derivatives of thiosalicylic acid as ligands have been synthesized and characterized by microanalysis, IR, 1H and 13C NMR...     

Semiconducting In2S3 quantum dots in thin film form: sonochemical versus conventional chemical synthesis and investigation of their structural and optical properties

Indium(III) sulfide quantum dots were deposited in thin film form using both a conventional chemical bath deposition method and a sonochemical route. The developed routes allow deposition of cubic α-In₂S₃ nanocrystals in thin film form. The as-deposited films produced by the conventional and sonochemical approaches are highly nanocrystalline, with average crystal sizes of 2.5 and 2.0 nm correspondingly (as determined from the Scherrer formula), which increase to 4.1 nm upon annealing treatment, due to coalescence and crystal-growth processes. Refinement of the lattice-constant value in the case of as-deposited and annealed films was performed using linear regression analysis. Blue-shifted band-gap energy values of as-deposited films with respect to those corresponding to bulk specimen, accompanied with the red shift of absorption onset upon annealing, strongly indicate the quantum-dot behavior of the synthesized nanocrystals. The detected three-dimensional quantum-confinement effects in the synthesized nanocrystals were discussed in terms of the Brus model. On the basis of optical spectroscopic data, we estimated the Bohr's excitonic radius value in this semiconductor. Presented at the X-th Symposium on Suface Physics, Prague, Czech Republic, July 11–15, 2005.     

New (sqrt3 xsqrt 3)R30 degrees phase of Pb on Ge(111) and its consequence for the melting transition

Depending on the preparation method, we find two different structures of the Pb/Ge(111) system at a nominal coverage of 4 / 3 monolayer that exhibit different melting points. One is the well studied beta phase that melts at 270 degrees C, but the other is a new and metastable phase that melts at 330 degrees C. Using surface x-ray diffraction the atomic structure of both phases is found to be surprisingly similar. The difference in melting points can be explained by the distribution of the excess Pb present on the surface, which has a direct effect on the vacancy density. We propose a modified phase diagram, in which the melting temperature of the beta phase depends strongly on coverage.     

Application potential of liquid-phase acoustic wave devices as chemical and biochemical sensors

Summary Theoretical concept and potential ability of the bulk acoustic wave device as a liquid-phase sensor are discussed. The sensitivity of the sensor to liquid medium properties and to the device liquid-solid interface were evaluated. The surface free energy and interfacial viscosity are proved to have significant influence in determining the frequency responses, besides the effect of added mass. The experiments with biomolecules in the form of enzymes enhanced the selective detection capability and the potential of liquid-phase immunosensors application.     

Electrosynthesis of hydrogen peroxide via the reduction of oxygen assisted by power ultrasound

The electrosynthesis of hydrogen peroxide using the oxygen reduction reaction has been studied in the absence and presence of power ultrasound in a non-optimized sono-electrochemical flow reactor (20 cm cathodic compartment length with 6.5 cm inner diameter) with reticulated vitreous glassy carbon electrode (30 x 40 x 10 mm, 10 ppi, 7 cm(2)cm(-3)) as the cathode. The effect of several electrochemical operational variables (pH, volumetric flow, potential) and of the sono-electrochemical parameters (ultrasound amplitude and horn-to-electrode distance) on the cumulative concentration of hydrogen peroxide and current efficiency of the electrosynthesis process have been explored. The application of power ultrasound was found to increase both the cumulative concentration of hydrogen peroxide and the current efficiency. The application of ultrasound is therefore a promising approach to the increased efficiency of production of hydrogen peroxide by electrosynthesis, even in the solutions of lower pH (<12). The results demonstrate the feasibility of at-site-of-use green synthesis of hydrogen peroxide.     

Antioxidant activities of Melittis melissophyllum L. (Lamiaceae)

Extracts of Melittis melissophyllum leaves in ether, chloroform, ethyl acetate, n-butanol and water were evaporated to dryness and dissolved in 50% ethanol to make 10% (w/v) solutions. The potential protective action of the extracts was assessed by the corresponding in vitro and in vivo tests. In the in vitro experiments extracts were tested as potential scavengers of free radicals (DPPH, O?·?, NO, and OH radicals), as well as inhibitors of liposomal peroxidation (LPx). The results obtained show that all extracts (exept n-BuOH extract) are good scavengers of radicals and reduce LPx intensity in liposomes, which points to their protective (antioxidant) activity. In vivo experiments were concerned with antioxidant systems (activities of GSHPx, GSHR, Px, CAT, XOD, GSH content and intensity of LPx) in liver homogenate and blood-hemolysate of experimental animals after their treatment with extracts of M. melissophyllum leaves, or in combination with CCl?. On the basis of the results obtained it can be concluded that the examined extracts have protective (antioxidative) effect and this antioxidative behaviour is more pronounced in liver than in blood-hemolysate. The reason is probably the fact that liver contains other enzymatic systems, which can also participate in the antioxidative mechanism. Of all the extracts the H?O one showed the highest protective activity.     

Some Considerations in Relation to the Matrix Equation AXB = C

In this paper we represent a new form of condition for the consistency of the matrix equation AXB = C. If the matrix equation AXB = C is consistent, we determine a form of general solution which contains both reproductive and non-reproductive solutions. Also, we consider applications of the concept of reproductivity for obtaining general solutions of some matrix systems which are in relation to the matrix equation AXB = C.     

Retention mechanism assessment and method development for the analysis of iohexol and its related compounds in hydrophilic interaction liquid chromatography

Hydrophilic interaction liquid chromatography (HILIC) has emerged in recent years as a valuable alternative to reversed-phase liquid chromatography in the analysis of polar compounds. Research in HILIC is divided into two directions: the assessment of the retention mechanism and retention behavior, and the development of HILIC methods. In this work, four polar neutral analytes (iohexol and its related compounds A, B, and C) were analyzed on two silica and two diol columns in HILIC mode with the aim to investigate thoroughly the retention mechanisms and retention behavior of polar neutral compounds on these four columns. The adsorption and partition contribution to the overall HILIC retention mechanism was investigated by fitting the retention data to linear (adsorption and partition) and nonlinear (mixed-retention and quadratic) theoretical models. On the other hand, the establishment of empirical second-order polynomial retention models on the basis of D-optimal design made possible the estimation of the simultaneous influence of several mobile-phase-related factors. Furthermore, these models were also used as the basis for the application of indirect modeling of the selectivity factor and a grid point search approach in order to achieve the optimal separation of analytes. After the optimization goals had been set, the grids were searched and the optimal conditions were identified. Finally, the optimized method was subjected to validation.

A novel C,D-spirolactone analogue of paclitaxel: autophagy instead of apoptosis as a previously unknown mechanism of cytotoxic action for taxoids

The design, synthesis and biological evaluation of a novel C,D-spirolactone analogue of paclitaxel is described. This is the first paclitaxel analogue without an oxetane D-ring that shows a significant cytotoxic effect (activity one order of magnitude lower than paclitaxel). More importantly, its cytotoxicity is a result of a different mechanism of action, involving mTOR inhibition-dependent autophagy instead of G(2)/M cell cycle arrest-dependent apoptosis.     

The d10 route to dye-sensitized solar cells: step-wise assembly of zinc(II) photosensitizers on TiO2 surfaces

Dye-sensitized solar cells have been assembled using a sequential approach: a TiO(2) surface was functionalized with an anchoring ligand, followed by metallation with Zn(OAc)(2) or ZnCl(2), and subsequent capping with a chromophore functionalized 2,2':6',2'-terpyridine; the DSCs exhibit surprisingly good efficiencies confirming the effectiveness of the new strategy for zinc-based DSC fabrication.