A photochemical method for patterning the immobilization of ligands and cells to self-assembled monolayers

This work describes a chemically well defined method for patterning ligands to self-assembled monolayers (SAMs) of alkanethiolates on gold. This method begins with monolayers presenting a nitroveratryloxycarbonyl (NVOC)-protected hydroquinone which is photochemically irradiated to reveal a hydroquinone group. The resulting hydroquinone is then oxidized to the corresponding benzoquinone, providing a site for the Diels-Alder mediated immobilization of ligands. The rate constant for the photochemical deprotection is 0.032 s(-1) (with an intensity of approximately 100 mW/cm(2) between 355 and 375 nm), corresponding to a half-life of 21 s. The hydroquinone is oxidized to the benzoquinone using either electrochemical or chemical oxidation and then functionalized by reaction with a cyclopentadiene-tagged ligand. Two methods for patterning the immobilization of ligands are described. In the first, the substrate is illuminated through a mask to generate a pattern of hydroquinone groups, which are elaborated with ligands. In the second method, an optical microscope fit with a programmable translational stage is used to write patterns of deprotection which are then again elaborated with ligands. This technique is characterized by the use of well-defined chemical reactions to control the regions and densities of ligand immobilization and will be important for a range of applications that require patterned ligands for biospecific interactions.     

A comparative kinetic and mechanistic study of glutamic acid oxidation by acid permanganate in the absence and presence of sodium dodecyl sulphate

The kinetics and mechanism of glutamic acid (GCO₂H) oxidation by acid permanganate has been carried out in the absence and presence of sodium dodecyl sulphate (SDS). The surfactant enhances the reaction rate without changing the reaction mechanism. The overall rate expression for the reduction of Mn^VII may be written:

Growth promotion of HepG2 hepatoma cells by antisense-mediated knockdown of glypican-3 is independent of insulin-like growth factor 2 signaling

Glypican-3 (GPC3) encodes a cell-surface heparan- sulfate proteoglycan and its expression is frequently silenced in ovarian cancer, mesotheliomas, and breast cancer cell lines and ectopic expression of GPC3 inhibited the growth of these cells, suggesting that GPC3 plays a negative role in cell proliferation. In contrast, up-regulation of GPC3 is often observed in hepatoma, neuroblastoma, and Wilms' tumor. Whether GPC3 plays the same growth inhibitory role in these tumors remains to be studied. Here we report that antisense-mediated knockdown of GPC3 in the HepG2 hepatoma cells significantly promotes the growth of hepatoma cells. In addition, we show that this growth promotion is independent of insulin-like growth factor 2 (IGF2) signaling. Our data suggest that GPC3 plays a growth-suppressing role in hepatoma and provide cell biological evidence inconsistent with the hypothesis that GPC3 acts as a growth suppressor by downregulating IGF2.     

9,9-diphenyl-1,9,10,10a-tetrahydro-2H-phenaleno[1,9-bc]pyrans

Reaction between some naphtho[2,1-b]pyrans and 1,1-diphenylethene affords 9,9-diphenyl-1,9,10,10a-tetrahydro-2H-phenaleno[1,9-bc]pyrans.     

Sensitive and selective spectrophotometric method for the determination of trace amounts of osmium with 1,2,3-indanetrione monothiosemicarbazone

Summary Sensitive and Selective Spectrophotometric Method for the Determination of Trace Amounts of Osmium with 1,2,3-Indanetrione Monothiosemicarbazone A simple, sensitive and selective spectrophotometric method has been developed for the determination of osmium using 1,2,3-indane-trione monothiosemicarbazone (ITMT). The method is based on the colour reaction between ITMT and osmium(VIII) in hydrochloric acid (0.32–0.60 M) medium. The calibration graph for measurement at 440 nm is linear in the range 1.4–33.6g of osmium per 25ml, with a molar absorptivity of 6.43×10⁴l·mole^–1·cm^–1. The effect of interferences has been studied and the method applied to the determination of osmium in synthetic samples whose composition correspond to osmiridium or syserkite, with good results.     

Determination of mercury by radiochemical displacement method

A radiochemical displacement method for the determination of micro amounts of Hg(II) has been developed. 65Zn was displaced from the Zn-1-(2-pyridylazo-2-naphthol) complex at pH 5 in borate buffers by Hg (II). 10-80 micrograms of mercury could be determined. Interference of various metal ions and methods for suppression have also been carried out.     

Retention, kinetics and thermodynamics profile of cadmium adsorption from iodide medium onto polyurethane foam and its separation from zinc bulk

The sorption behaviour of 2.5 × 10⁻⁵ M solution of Cd(II) on polyurethane foam (PUF) from iodide medium have been investigated. The conditions were optimized from aqueous solutions of different pH (1-10) and of acids of varied concentration (0.01-1.0 M). The maximum concentration of KI was found to be 0.24 M and equilibration time was established to be 20 min. The data successfully followed the Freundlich and Dubinin-Radushkevich (D-R) isotherms at low metal ion concentration while Langmuir isotherm followed at higher metal ion concentration. The Freundlich parameter 1/n = 0.66 ± 0.02 have been evaluated whereas D-R isotherm yields the sorption free energy E = 10.5 ± 0.1 kJ mol⁻¹ indicating ion exchange type chemisorption. The monolayer coverage (XL) constant of Langmuir isotherm was found to be 23.7 ± 0.4 mg g⁻¹. The numerical values of thermodynamics parameters enthalpy (ΔH), entropy (ΔS) and Gibbs free energy (ΔG) indicated the endothermic and spontaneous nature of sorption. The Scatchard plot analysis was tested to evaluate the binding sites of the PUF and stability constants of sorption were determined. On the basis of these parameters, the sorption mechanism was discussed. Among the foreign ions tested, Pb(II), Hg(II), cyanide and nitrite should be absent. The clean separation of Cd(II) from Zn(II) ions in the ratio 1:250, respectively, was achieved by column chromatography.     

Total synthesis of (+)-xyloketal D, a secondary metabolite from the mangrove fungus Xylaria sp.

(+)-Xyloketal D was prepared in a one-pot multistep domino reaction by heating optically active 5-hydroxy-4-methyl-3-methylenepentan-2-one (R) in toluene with 2,4-dihydroxyacetophenone. The absolute configuration of the natural product was confirmed by preparation of the starting enone from a lactone of established absolute configuration.     

Hall effects and entropy generation applications for peristaltic flow of modified hybrid nanofluid with electroosmosis phenomenon

The electroosmotic peristaltic flow of modified hybrid nanofluid in presence of entropy generation has been presented in this thermal model. The Hall impact and thermal radiation with help of nonlinear relations has also been used to modify the analysis. The assumed flow is considered due to a non-uniform trapped channel. The properties of modified hybrid nanofluid model are focused with interaction of three distinct types of nanoparticles namely copper ($Cu)$, silver ($Ag$) and aluminum oxide ($A{l}_2{O}_3).$ The mathematical modeling and significances of entropy generation and Bejan number are identified. With certain flow assumptions, the governing equations are attained for optimized peristaltic electroosmotic problem. Widely used assumptions of long wave length and low Reynolds number reduced the governing equations in ordinary differential equations. The ND solver is flowed for the solution process. The physical significant of results is observed by assigning the numerical values to parameters.     

The bis-phenyltin-substituted, lone-pair-containing tungstoarsenate [(C(6)h(5)Sn)(2)as(2)W(19)O(67)(H(2)O)](8)(-)

The bis-phenyltin-substituted, lone-pair-containing tungstoarsenate [(C(6)H(5)Sn)(2)As(2)W(19)O(67)(H(2)O)](8)(-) (1) has been synthesized and characterized by multinuclear NMR, IR, and elemental analysis. Single-crystal X-ray analysis was carried out on (NH(4))(7)Na[(C(6)H(5)Sn)(2)As(2)W(19)O(67)(H(2)O)].17.5H(2)O (NH(4)(-1), which crystallizes in the monoclinic system, space group P2(1)/c, with a = 18.3127(17) A, b = 24.403(2) A, c = 22.965(2) A, beta = 106.223(2) degrees, and Z = 4. Polyanion 1 consists of two B-alpha-(As(III)W(9)O(33)) Keggin moieties linked via a WO(H(2)O) fragment and two SnC(6)H(5) groups leading to a sandwich-type structure with nominal C(2)(v) symmetry. Polyanion 1 is stable in solution as indicated by the expected 6-line pattern (4:4:4:4:2:1) in (183)W NMR and the expected (119)Sn, (13)C, and (1)H NMR spectra. Synthesis of 1 was accomplished by reaction of C(6)H(5)SnCl(3) and K(14)[As(2)W(19)O(67)(H(2)O)] in a 2:1 molar ratio in aqueous acidic medium (pH 2). In the solid-state structure of NH(4)(-1, neighboring polyanions are weakly bound via W-O-Na bonds leading to chains which interact with each other via the phenyl rings resulting in a 2-D assembly.