Analyse de films minces et ultra-minces: Perspectives nouvelles en spectrométrie d'émission des rayons X

This paper illustrates the capabilities of “low-energy electron induced X-ray spectrometry” (LEEIXS) for surface and thin, or ultra-thin, film analysis. The work deals with anodic films and shows that it is possible to measure oxide film thicknesses in a range between 0 and a few hundred angströms. In addition, it is demonstrated that this technique provides some information about the distribution of impurities in the interior of the films.     

Pinning of an interface by a weak potential

We prove that in a two-dimensional Gaussian SOS model with a small attractive potential the height of the interface remains bounded no matter how small the potential is; this is in sharp contrast with the free situation in which the interface height diverges logarithmically in the thermodynamic limit.     

Fluorescence Correlation Spectroscopy of the Binding of Nucleotide Excision Repair Protein XPC-hHr23B with DNA Substrates

The interaction of the nucleotide excision repair (NER) protein dimeric complex XPC-hHR23B, which is implicated in the DNA damage recognition step, with three Cy3.5 labeled 90-bp double-stranded DNA substrates (unmodified, with a central unpaired region, and cholesterol modified) and a 90-mer single-strand DNA was investigated in solution by fluorescence correlation spectroscopy. Autocorrelation functions obtained in the presence of an excess of protein show larger diffusion times (tau (d)) than for free DNA, indicating the presence of DNA-protein bound complexes. The fraction of DNA bound (theta), as a way to describe the percentage of protein bound to DNA, was directly estimated from FCS data. A significantly stronger binding capability for the cholesterol modified substrate (78% DNA bound) than for other double-stranded DNA substrates was observed, while the lowest affinity was found for the single-stranded DNA (27%). This is in accordance with a damage recognition role of the XPC protein. The similar affinity of XPC for undamaged and 'bubble' DNA substrates (58% and 55%, respectively) indicates that XPC does not specifically bind to this type of DNA substrate comprising a large (30-nt) central unpaired region.     

Intercepted-Knoevenagel condensation for the synthesis of unsymmetrical fused-tricyclic 4H-pyrans

4H-Pyrans (4H-Pys) and 1,4-dihydropyridines (1,4-DHPs) are important classes of heterocyclic scaffolds in medicinal chemistry. Herein, an indium(III)-catalyzed one-pot domino reaction for the synthesis of highly functionalized 4H-Pys, and a model of 1,4-DHP is reported. This alternative approach to the challenging Hantzsch 4-component reaction enables the synthesis of fused-tricyclic heterocycles, and the mechanistic studies underline the importance of an intercepted-Knoevenagel adduct to achieve higher chemoselectivity towards these types of unsymmetrical heterocycles.     

Point-mutation effects on charge-transport properties of the tumor-suppressor gene p53

We report on a theoretical study of point mutations effects on charge transfer properties in the DNA sequence of the tumor-suppressor p53 gene. On the basis of effective tight-binding models which simulate hole propagation along the DNA, a statistical analysis of mutation-induced charge transfer modifications is performed. In contrast to noncancerous mutations, mutation hot spots tend to result in significantly weaker changes of transmission properties. This suggests that charge transport could play a significant role for DNA-repairing deficiency yielding carcinogenesis.     

A note on dual modules and the transpose

Archiv der Mathematik - It is a classical result in matrix algebra that any square matrix over a field can be conjugated to its transpose by a symmetric matrix. For F a non-Archimedean local field,...     

A Kinetic Dearomatization Strategy for an Expedient Biomimetic Route to the Bielschowskysin Skeleton

Bielschowskysin ( 1 ), the flagship of the furanocembranoid diterpene family, has attracted attention from chemists owing to its intriguing and daunting polycyclic architecture and medicinal potential against lung cancer. The high level of functionalization of 1 poses a considerable challenge to synthesis. Herein, a stereoselective furan dearomatization strategy of furanocembranoids was achieved via the intermediacy of chlorohydrins. The stereochemical course of the kinetic dearomatization was established, and the C3 configuration of the resulting exo‐enol ether intermediates proved to be essential to complete the late‐stage transannular [2+2] photocycloaddition. Overall, this biomimetic strategy starting from the natural product acerosolide ( 9 ) featured an unprecedented regio‐ and highly stereoselective furan dearomatization, which provided rapid access to the pivotal exo‐enol ethers en route to the intricate bielschowskyane skeleton.