Binding of a Telomestatin Derivative Changes the Mechanical Anisotropy of a Human Telomeric G‐Quadruplex

Mechanical anisotropy is an essential property for biomolecules to assume structural and functional roles in mechanobiology. However, there is insufficient information on the mechanical anisotropy of ligand–biomolecule complexes. Herein, we investigated the mechanical property of individual human telomeric G‐quadruplexes bound to telomestatin, using optical tweezers. Stacking of the ligand to the G‐tetrad planes changes the conformation of the G‐quadruplex, which resembles a balloon squeezed in certain directions. Such a squeezed balloon effect strengthens the G‐tetrad planes, but dislocates and weakens the loops in the G‐quadruplex upon ligand binding. These dynamic interactions indicate that the binding between the ligand and G‐quadruplex follows the induced‐fit model. We anticipate that the altered mechanical anisotropy of the ligand–G‐quadruplex complex can add additional level of regulations on the motor enzymes that process DNA or RNA molecules.     

Anisotropie der Polarisierbarkeit des Monomerbausteins in amorphen Polymeren

Zusammenfassung Es wird eine Methode vorgestellt, mit der durch quantitative Erfassung der mittleren Molekelorientierung sowie durch Bestimmung der makroskopischen Doppelbrechung an orientierten Proben die Anisotropie der Polarisierbarkeit der Monomerbausteine für amorphe Polymere im Glaszustand ermittelt werden kann. Diese Anisotropie erweist sich zumindest für PMMA und PVC als recht klein im Vergleich zu derjenigen von Molekeln niedermolekularer Substanzen. Aufgrund der starken Polarisierbarkeit des Benzolringes ist die Anisotropie beim Grundbaustein für Polystyrol wesentlich höher.Mit 9 Abbildungen     

Anisotrope Wärmeleitfähigkeit in Polymeren

Ohne ZusammenfassungMit 24 Abbildungen     

各向异性介质中Ⅲ型半无限长裂纹的匀速扩展

本文用Laplace变换、Wiener-Hopf和Cagniard-de Hoop方法求解了各向异性介质中一半无限长Ⅲ型裂纹突然以匀速扩展的问题.给出了瞬态的位移场和运动裂纹尖端的动态应力强度因子.     

Positivité de la dissipation intrinsèque d'une classe de modèles d'endommagement anisotropes non standardsPositivity of intrinsic dissipation of a class of nonstandard anisotropic damage models

A nonstandard thermodynamics framework ensures the positivity of the dissipation due to degradation mechanisms for damage states represented by a symmetric second order tensor. The proof of the positivity of the intrinsic dissipation is given. An increasing damage, in terms of positive principal values of the damage rate tensor, guaranties this positivity for the considered class of models, extending then to induced anisotropy the isotropic case property of a positive damage rate. This result gives many possibilities of modeling for anisotropic damage. To cite this article: R. Desmorat, C. R. Mecanique 334 (2006).     

A model for solid-state dewetting of a fully-faceted thin film

Owing to their extremely aspect ratios, most thin films are unstable and when they are heated, they will dewet or agglomerate to form islands. This process can occur in the solid state through capillary-driven surface self-diffusion. A key feature of the dewetting process is the retraction of the edges of the film, either natural edges, patterned edges, or edges where holes have formed. Models of edge retraction have been previously developed for isotropic materials and anisotropic materials with differentiable surfaces, but the effects of faceting in highly anisotropic materials have been largely unexplored. Here, we present a two-dimensional model of edge retraction for highly anisotropic, fully-faceted thin films. This model shows generally good agreement with experimental results for edge retraction of single-crystal Ni films on MgO. In both experiments and the model, rims form as the edges retract. The effects of adjusting various physical parameters on the edge retraction rate and the evolving rim geometry were explored using the model. The film thickness, surface self-diffusivity on the top facet of the rim, the equivalent contact angle of the film on the substrate, and the absolute value of the surface energies were found to be the factors that have the greatest influence on the edge retraction rate. In isotropic models and some experimental systems, valleys form ahead of the retracting rims and deepen to contact the substrate and cause pinch-off. Our model suggests that this form of pinch-off will not occur when the rim is fully faceted and the top surface is an equilibrium facet. However, pinch-off can occur through film thinning and for films with top surfaces that do not form flat equilibrium facets.