Functionalized Tricyclic Cytosine Analogues Provide Nucleoside Fluorophores with Improved Photophysical Properties and a Range of Solvent Sensitivities

Tricyclic cytosines (tC and tC^O frameworks) have emerged as a unique class of fluorescent nucleobase analogues that minimally perturb the structure of B‐form DNA and that are not quenched in duplex nucleic acids. Systematic derivatization of these frameworks is a likely approach to improve on and diversify photophysical properties, but has not so far been examined. Synthetic methods were refined to improve on tolerance for electron‐donating and electron‐withdrawing groups, resulting in a series of eight new, fluorescent cytidine analogues. Photophysical studies show that substitution of the framework results in a pattern of effects largely consistent across tC and tC^O and provides nucleoside fluorophores that are brighter than either parent. Moreover, a range of solvent sensitivities is observed, offering promise that this family of probes can be extended to new applications that require reporting on the local environment.     

Robust and Adhesive Hydrogels from Cross‐Linked Poly(ethylene glycol) and Silicate for Biomedical Use

A systematic approach to develop robust and adhesive hydrogels by photopolymerizing poly(ethylene glycol) (PEG)‐diacrylate and methoxy‐PEG‐acrylate in the presence of charged silicate nanoparticles (Laponite) is presented. PEG‐diacrylate and silicate are used for covalent and physical cross‐linking, thus providing the hydrogel with mechanical and adhesive strengths. Methoxy‐PEG‐acrylate is used as a softening agent. The resulting hydrogels can be extensively elongated and the hydrogels readily adhere to tissue even in the elongated state. These hydrogels may aid the development of adhesive tissue engineering matrixes, wound dressings, sealants, and the adhesive components of biomedical devices.

     

Hochdrucksynthese und Struktur von Rb2PtH6 und Cs2PtH6, ternären Hydriden mit K2PtCl6-Struktur

High-pressure Synthesis and Structure of Rb₂PtH₆ and Cs₂PtH₆, Ternary Hydrides with K₂PtCl₆-Structure The ternary platinum hydrides Rb₂PtH₆ and Cs₂PtH₆ were synthesized by the reaction of rubidium hydride and cesium hydride, respectively, with platinum sponge under a hydrogen pressure above 1 500 bar at 500°C. X-ray investigations on powdered samples and elastic neutron diffraction experiments on the deuterated compounds at the time-of-flight spectrometer POLARIS led to their complete structure determination. Their atomic arrangements are isotypic with that of K₂PtCl₆ containing isolated [PtH₆]^2?-octahedra (space group: Fm3 m, Z = 4).     

The Veronese surface revisited

Recently, the classical Veronese surface reemerged in the context of the application oriented field of Computer Aided Geometric Design due to its interesting relation to rational triangular Bézier surfaces. This motivated the investigation of Veronese varieties presented in this paper. It is shown that the general degree Veronese surface forms a singular subvariety of certain algebraic varieties. This general result is then further examined and extended in the low-degree cases . Received 3 May 2000.     

Minor groove binders and drugs targeting proteins cover complementary regions in chemical shape space

DNA minor groove binders (MGBs) are known to influence gene expression and are therefore widely studied to explore their therapeutic potential. We identified shape-based virtual screening with ROCS as a highly effective computational approach to enrich known MGBs in top-ranked molecules. Discovery of ten previously unknown MGBs by shape-based screening further confirmed the relevance of ligand shape for minor groove affinity. Based on experimental testing we propose three simple rules (at least two positive charges, four nitrogen atoms, and one aromatic ring) as filters to reach even better enrichment of true positives in ROCS hit lists. Interestingly, shape-based ranking of MGBs versus FDA-approved drugs again leads to high enrichment rates, indicating complementary coverage of chemical shape space and indicating minor groove affinity to be unfavorable for approval of drugs targeting proteins.     

The Stokes problem in a periodic layer

We construct and justify the asymptotic representation at infinity of solutions to the Stokes problem in a three‐dimensional domain with periodic geometric structure, which is bounded in one dimension, e.g., a periodically perforated layer. © 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

Nanocomposite polymer hydrogels

The technological need for new and better soft materials as well as the drive for new knowledge and fundamental understanding has led to significant advances in the field of nanocomposite gels. A variety of complex gel structures with unique chemical, physical, and biological properties have been engineered or discovered at the nanoscale. The possibility to form self-assembled and supramolecular morphologies makes organic polymers and inorganic nanoparticles desirable building blocks for the design of water based gels. In this review, we highlight the most recent (2004–2008) accomplishments and trends in the field of nanocomposite polymer hydrogels with a focus on creative approaches to generating structures, properties, and function within mostly biotechnological applications. We examine the impact of published work and conclude with an outline on future directions and challenges that come with the design and engineering of new nanocomposite gels.