Micelle-like macromolecular systems for controlled release of daunomycin

Soluble macromolecular conjugates for the delivery of the strongly hydrophobic anticancer drug daunomycin (DM) or rubomycin with its controlled release were prepared. The solution properties of these conjugates consisting of DM bonded to copolymer of maleic anhydride and divinyl ether (DIVEMA) and a few model compounds were investigated using adsorbance spectroscopy, as well as surface activity and solubilization of water-insoluble dye measurements. The data of these studies indicated that in water solutions conjugates are associated, probably intramolecularly. This micellization in parallel with an H-bonded ionic complex between DM and polymer carrier determines the DM release. It is concluded that the desirable drug release can be achieved through changing the structure of conjugates by means of varying the constituents hydrophobicity. © 1998 John Wiley & Sons, Ltd.     

Ethenedithione (S=C=C=S): Does It Obey Hund's Rule?

Significantly higher in energy (24 kJ mol⁻¹) than the triplet ground state (³Σ_g⁻) is the ¹Δ_g state of ethenedithione (S=C=C=S), in agreement with Hund's rule. This result was obtained from high-level ab initio calculations. Thus, ethenedithione cannot, as had been proposed, be considered as the first example for the violation of Hund's rule in an equilibrium structure.     

Americium preferred: lanmodulin,a natural lanthanide-binding protein favors an actinide over lanthanides

The separation and recycling of lanthanides is an active area of research with a growing demand that calls for more environmentally friendly lanthanide sources. Likewise, the efficient and industrial separation of lanthanides from the minor actinides (Np, Am–Fm) is one of the key questions for closing the nuclear fuel cycle; reducing costs and increasing safety. With the advent of the field of lanthanide-dependent bacterial metabolism, bio-inspired applications are in reach. Here, we utilize the natural lanthanide chelator lanmodulin and the luminescent probes Eu³⁺ and Cm³⁺ to investigate the inter-metal competition behavior of all lanthanides (except Pm) and the major actinide plutonium as well as three minor actinides neptunium, americium and curium to lanmodulin. Using time-resolved laser-induced fluorescence spectroscopy we show that lanmodulin has the highest relative binding affinity to Nd³⁺ and Eu³⁺ among the lanthanide series. When equimolar mixtures of Cm³⁺ and Am³⁺ are added to lanmodulin, lanmodulin preferentially binds to Am³⁺ over Cm³⁺ whilst Nd³⁺ and Cm³⁺ bind with similar relative affinity. The results presented show that a natural lanthanide-binding protein can bind a major and various minor actinides with high relative affinity, paving the way to bio-inspired separation applications. In addition, an easy and versatile method was developed, using the fluorescence properties of only two elements, Eu and Cm, for inter-metal competition studies regarding lanthanides and selected actinides and their binding to biological molecules.

In need of environmentally friendly methods for the separation and recycling of lanthanides and actinides, the binding of the protein lanmodulin to lanthanides and actinides was studied using time resolved laser induced fluorescence spectroscopy.     

Next-generation aqueous flow battery chemistries

The battery industry is seeking solutions for large-scale energy storage that are affordable, durable, and safe. Aqueous redox flow batteries (RFBs) have the inherent properties to meet these requirements. While much has been learned over the past decade on the properties of redox materials, the focus of next-generation systems must be primarily on lowering redox material cost and increasing durability. In this context, in addition to inexpensive materials such as iron salts, redox couples based on small organic molecules have shown significant promise. A considerable level of understanding has been gained on the factors affecting the durability of aqueous RFB systems, specifically relating to molecular stability and crossover. New molecular classes, substituent strategies, and cell configurations have been identified to enhance the durability of systems in the future. Next-generation systems will also need to focus on designing molecules for achieving high energy efficiency and power density as well. Furthermore, the application of computational methods for screening of chemical stability could accelerate discovery of new molecular architectures.     

Unexpected Kinetics in the Polymerization of Ethene by Cp$\rm{ {_{2}^{{\ast}}}}$ZrCl2/MAO

A sterically hindered metallocene catalyst, Cp ZrCl₂ activated with methylaluminoxane (MAO), is found to polymerize ethene at temperatures up to 60° with a good propagation rate constant but low number of active sites, and with negligible β‐hydride elimination or β‐hydride transfer to monomer. Moreover, transmetalation to Al is found to be effectively irreversible for alkyl groups larger than Me. With the major mechanisms for chain transfer and termination suppressed, one might expect a living polymerization. The bulk polymerization of ethene was indeed found to be quasi‐living even when performed at well above room temperature, and furthermore provided rate constants which agreed remarkably well with those from the mass‐spectrometric study.     

Laser-induced structural changes in pure GeO2 glasses

We report on the characterization of structural modifications created by micro-explosions at the beam waist of a tightly focused femtosecond laser pulse inside of GeO₂ glass. Micro-Raman scattering revealed the presence of structurally strongly modified regions at and around the irradiated sites. For separations of 5 μm between adjacent irradiated sites structural modifications due to a pressure increase are observed, whereas smaller spacings of 2 μm lead to thermal effects and crystallization. The mechanisms and the interplay of pressure and temperature effects are discussed.     

The structure of compact disjointness preserving operators on continuous functions

Let T be a compact disjointness preserving linear operator from C₀(X) into C₀(Y), where X and Y are locally compact Hausdorff spaces. We show that T can be represented as a norm convergent countable sum of disjoint rank one operators. More precisely, T = Σ_n δ ?h_n for a (possibly finite) sequence {x_n }_n of distinct points in X and a norm null sequence {h_n }_n of mutually disjoint functions in C₀(Y). Moreover, we develop a graph theoretic method to describe the spectrum of such an operator (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)