Cystobactamids: Myxobacterial Topoisomerase Inhibitors Exhibiting Potent Antibacterial Activity

The development of new antibiotics faces a severe crisis inter alia owing to a lack of innovative chemical scaffolds with activities against Gram‐negative and multiresistant pathogens. Herein, we report highly potent novel antibacterial compounds, the myxobacteria‐derived cystobactamids 1 – 3 , which were isolated from Cystobacter sp. and show minimum inhibitory concentrations in the low μg mL^?1 range. We describe the isolation and structure elucidation of three congeners as well as the identification and annotation of their biosynthetic gene cluster. By studying the self‐resistance mechanism in the natural producer organism, the molecular targets were identified as bacterial type IIa topoisomerases. As quinolones are largely exhausted as a template for new type II topoisomerase inhibitors, the cystobactamids offer exciting alternatives to generate novel antibiotics using medicinal chemistry and biosynthetic engineering.     

Old Selenium Heterocycles Revisited: Synthesis,Spectroscopic, and Structural Characterization of N‐Acyl‐1,3‐selenazol‐2(3H)‐imines and 5‐Acyl‐1,3‐selenazol‐2‐amines from Acylselenourea Derivatives

A series of five‐membered selenium heterocycles was prepared from the reaction of various selenoureas and phenacyl bromides. In the case of 1‐acyl‐3‐arylselenoureas N‐acyl‐1,3‐selenazol‐2(3H)‐imines are formed, whereas the analogous reaction with 3,3‐disubstituted 1‐acylselenoureas affords 5‐acyl‐1,3‐selenazol‐2‐amines. The compounds were characterized by NMR spectroscopy and mass spectrometry. In addition, the proposed structures were unambiguously confirmed by X‐ray diffraction studies.     

Carbohydrate‐Based Nanocarriers Exhibiting Specific Cell Targeting with Minimum Influence from the Protein Corona

Whenever nanoparticles encounter biological fluids like blood, proteins adsorb on their surface and form a so‐called protein corona. Although its importance is widely accepted, information on the influence of surface functionalization of nanocarriers on the protein corona is still sparse, especially concerning how the functionalization of PEGylated nanocarriers with targeting agents will affect protein corona formation and how the protein corona may in turn influence the targeting effect. Herein, hydroxyethyl starch nanocarriers (HES‐NCs) were prepared, PEGylated, and modified on the outer PEG layer with mannose to target dendritic cells (DCs). Their interaction with human plasma was then studied. Low overall protein adsorption with a distinct protein pattern and high specific affinity for DC binding were observed, thus indicating an efficient combination of “stealth” and targeting behavior.     

Extending the Scope of the B(C6F5)3‐Catalyzed CN Bond Reduction: Hydrogenation of Oxime Ethers and Hydrazones

The B(C₆F₅)₃‐catalyzed hydrogenation is applied to aldoxime triisopropylsilyl ethers and hydrazones bearing an easily removable phthaloyl protective group. The C?N reduction of aldehyde‐derived substrates (oxime ethers and hydrazones) is enabled by using 1,4‐dioxane as the solvent known to participate as the Lewis‐basic component in FLP‐type heterolytic dihydrogen splitting. More basic ketone‐derived hydrazones act as Lewis bases themselves in the FLP‐type dihydrogen activation and are therefore successfully hydrogenated in nondonating toluene. The difference in reactivity between aldehyde‐ and ketone‐derived substrates is also reflected in the required catalyst loading and dihydrogen pressure.     

High Aspect Ratio Vertical Cantilever RF-MEMS Variable Capacitor

An electrostatically actuated, microwave microelectromechanical system variable capacitor fabricated using deep X-ray lithography is presented. A single exposure has been used to produce the novel high aspect ratio microstructure, which includes a thin, vertically oriented, movable nickel cantilever beam and a 40:1 vertical aspect ratio capacitance gap. The 0.8-pF capacitor operates in the 1-5GHz region and has Q-factors of 36 at 4GHz and 133 at 2 GHz. The variable capacitance ratio is 1.24:1 over a 20-V tuning range at 4GHz     

Notizen zur Phosphors?urebestimmung

Ohne Zusammenfassung     

Die Reciprokenmethode bei Berechnung der Atomformeln insbesondere von Silicaten

Ohne Zusammenfassung     

Institutional Logics from the Aggregation of Organizational Networks: Operational Procedures for the Analysis of Counted Data

We address some problems of network aggregation that are central to organizational studies. We show that concepts of network equivalence (including generalizations and special cases of structural equivalence) are relevant to the modeling of the aggregation of social categories in cross-classification tables portraying relations within an organizational field (analogous to one-mode networks). We extend our results to model the dual aggregation of social identities and organizational practices (an example of a two-mode network). We present an algorithm to accomplish such dual aggregation. Within the formal and quantitative framework that we present, we emphasize a unified treatment of (a) aggregation on the basis of structural equivalence (invariance of actors within equivalence sets), (b) the study of variation in relations between structurally equivalent sets, and (c) the close connections between aggregation within organizational networks and multi-dimensional modeling of organizational fields.     

Evolution toward 4G wireless networking [Guest Editorial]

This special issue serves as a stimulus to promote and accelerate technological evolution toward 4G networking. The response to the call for papers for this issue is indicative of the great interest with which the community views this topic. Of the many high quality in depth and breadth papers received from both academia and industry around the world, we could only accommodate a selected few in this issue. The research on the next generation wireless networking involves many cutting-edge research topics, which are presented in some articles included in this special issue     

Zur Bestimmung des Kupfers und Eisens im Kupferkiese und Werkblei

Ohne Zusammenfassung