Dendritic molecular capsules for hydrophobic compounds

Reichardt's dye, a highly solvatochromic dye, was encapsulated within poly (glycerol succinic acid) ([Gn]-PGLSA-OH) dendrimers to investigate the interior environment of these dendritic macromolecules. The absorption maximum for the encapsulated Reichardt's dye in water was indicative of a relatively high dielectric constant present within the dye/dendrimer complex. (1)H NMR of the encapsulated complex showed the presence of aromatic protons from Reichardt's dye along with the aliphatic protons of the dendrimer. Additionally, there were substantial changes in T(1) and T(2) times of the encapsulated dye when compared with the free dye, and (1)H NOESY spectra for the complex showed a significant number of intermolecular NOE cross-peaks. These data reveal the close through-space proximity of the dye to the dendrimer and the restricted motion of the encapsulated dye. To demonstrate the potential use of these macromolecules as drug delivery vehicles, the poorly water-soluble anticancer drug 10-hydroxycamptothecin (10HCPT) was encapsulated within a carboxylated PGLSA dendrimer ([G4]-PGLSA-COONa). Cytotoxicity assays with human breast cancer cells showed a significant reduction of cell viability, demonstrating that 10HCPT retains activity upon encapsulation.     

Simultaneous analysis of oxidized and reduced glutathione in cell extracts by capillary zone electrophoresis

Glutathione (GSH) and glutathione disulfide (GSSG) levels in cells constitute a thiol redox system. They can be used as an indicator of oxidative stress of the cell. In this study, a capillary zone electrophoresis (CZE) method is described that enables quantitation of GSH and GSSG from cellular extracts. The CZE buffer used was 20 mM ammonium acetate containing 5% (v/v) acetic acid at pH 3.1 in conjunction with a polybrene coated capillary operated in reverse polarity mode. Effects of different acids used to prepare cell samples were investigated on CZE performance. The acids include meta phosphoric acid (MPA), trichloroacetic acid (TCA), phosphoric acid (PA) and sulfosalicylic acid (SSA) and are used to stabilize GSH and GSSG before performing CZE analysis. The method features a limit of detection of 4 microM and a limit of quantitation of 12 microM for both GSSG and GSH and recoveries of 94% for GSH and 100% for GSSG. Quantitative analysis of GSSG and GSH in HaCaT cell extracts (5% SSA, w/v) was performed with this method and changes in the ratio of GSH to GSSG in N-ethylmaleimide treated cell sample was observed by comparing with control cell samples.     

Advances in Catalysis. Volume 25; edited by D.D. Eley, H. Pines, and P.B. Weisz, Academic Press, New York, San Francisco and London, 1976, xii + 457 pages, $42.50

Photolysis of 1,2-divinyl- and 1-phenyl-2-vinyltetramethyldisilane and 1-phenylethenylpentamethyldisilane has been investigated. All three compounds afforded a new type of silicon—carbon double-bonded intermediate via photorearrangement of a silyl group to the terminal carbon of a vinyl group.     

Reactions of hydropolysilanes with alcohols catalysed by tris(triphenylphosphine)chlororhodium

[RhCl(PPh₃)₃] is a very effective catalyst for the cleavage of Si-Si bonds by alcohols.     

Mesoporous electrode material from alumina-stabilized anatase TiO2 for lithium ion batteries

A mesoporous electrode material whose structure is composed of anatase nanocrystals stabilized by alumina is reported. Powder X-ray diffraction shows the anatase phase only, but micro-Raman spectroscopy shows that the materials have a core-shell morphology with grains of bulk anatase covered by a thin rutile layer on the surface. This structure is unique when compared to analogous materials stabilized by zirconia (PNNL-1). Nitrogen adsorption isotherms demonstrate a monotonous increase in surface area and mesopore volume with increasing Al content. Thin film electrodes from these materials were characterized by lithium insertion electrochemistry. Cyclic voltammograms exhibit significant differences in Li accommodation in Al-free and Al-stabilized materials.     

Magnetism of metal cyanide networks assembled at interfaces

Studies of metal cyanide thin films prepared directly at interfaces are reviewed. The systems range from monolayers, single-layer analogs of Prussian blue-like networks, to bulk powders prepared as thin films. Monolayer networks are prepared at the air/water interface and transferred to solid supports using Langmuir-Blodgett film methods. Films of bulk materials are prepared directly on solid surfaces using a templated sequential deposition procedure. The magnetic properties of the films have been explored, and in some cases, these monolayers and surface films give rise to new behavior that is only possible because of the fabrication method or thin film architecture. The methods of synthesis can generate oriented samples, even when the materials are poorly crystalline. Furthermore, the interface-assembled networks are inherently anisotropic, leading to phenomena not present in the solid-state analogs, such as anisotropic photomagnetism in a thin film of Rb_jCo_k[Fe(CN)₆]_l·nH₂O.