Template-Directed Synthesis of Shape-Persistent Macrocyclic Amphiphiles with Convergently Arranged Functionalities

Macrocyclic structures such as 1 and rings with different polar substituents pointing inwards can be prepared by the intramolecular Glaser coupling of tetraacetylenes held covalently in position around a temporary template.     

Varför Tunneldioder?

In the last two years the electronic industry has shown a great interest in tunnel diodes. This article gives a short explanation of the basic effect and summarizes the more important features of the device. The general fabrication technique is outlined, and some associated problems are discussed.     

Untersuchungen an Chitin. 2. Mitt. Einflu? der Deacetylierung auf die L?slichkeit

Ohne Zusammenfassung     

Two-photon double ionization of helium: investigating the importance of correlation in the final state

In this paper, we present theoretical results for the process of non-sequential two-photon double ionization of helium at the photon energy 42 eV. Our approach is based on solving the time-dependent Schrödinger equation in a B-spline based numerical framework. Information about the process is obtained by extracting the double-ionized component by means of uncorrelated final states. The total (generalized) cross section for the process is extracted, as well as differential cross sections resolved in electron energies and ejection angles. We focus on the impact the final-state correlation has on the accuracy of the cross sections.     

Theoretical studies on the interaction of partial agonists with the 5-HT<Subscript>2A</Subscript> receptor

A series of 51 5-HT_2A partial agonistic arylethylamines (primary or benzylamines) from different structural classes (indoles, methoxybenzenes, quinazolinediones) was investigated by fragment regression analysis (FRA), docking and 3D-QSAR approaches. The data, pEC₅₀ values and intrinsic activities (E_max) on rat arteries, show high variability of pEC₅₀ from 4 to 10 and of E_max from 15 to 70%. FRA indicates which substructures affect potency or intrinsic activity. The high contribution of halogens in para position of phenethylamines to pEC₅₀ points to a specific hydrophobic pocket. Other results suggest the significance of hydrogen bonds of the aryl moiety for activation and the contrary effect of benzyl groups on affinity (increasing) and intrinsic activity (decreasing). Results from fragment regression and data on all available mutants were considered to derive a common binding site at the rat 5-HT_2A receptor. After generation and MD simulations of a receptor model based on the β₂-adrenoceptor structure, typical derivatives were docked, leading to the suggestion of common interactions, e.g., with serines in TM3 and TM5 and with a cluster of aromatic amino acids in TM5 and TM6. The whole series was aligned by docking and minimization of the complexes. The pEC₅₀ values correlate well with Sybyl docking energies and hydrophobicity of the aryl moieties. With this alignment, CoMFA and CoMSIA approaches based on a training set of 36 and a test set of 15 compounds were performed. The correlation of pEC₅₀ with steric, electrostatic, hydrophobic and H-bond acceptor fields resulted in sufficient fit (q ²: 0.75–0.8, r ²: 0.92–0.95) and predictive power (r _pred²: 0.85–0.88). The important interaction regions largely reflect the patterns provided by the putative binding site. In particular, the fit of the aryl moieties and benzyl substituents to two hydrophobic pockets is evident.     

Hierarchical self-assembly of polycyclic heteroaromatic stars into snowflake patterns

Seeing stars: The two-dimensional patterns of the polycyclic heteroaromatic star molecules 1 on graphite vary with the side chain length. For n=12, frustrated self-assembly leads to hierarchically organized superstructures: up to 10?molecules form triangular aggregates which pack densely into hexagonal patterns with very large (15.5?nm) lattice constants.