Protection and Labelling of Thymidine by a Fluorescent Photolabile Group

A fluorescent photolabile group including coumarin and MeNPOC moieties was synthesized to protect 5′‐OH terminal function of thymidine (T). Its photochemical and photophysical properties were studied, in particular the photocleavage (photodeprotection under a 365‐nm irradiation) is only lowered by a factor of two by addition of the fluorophore. Fluorescence properties of the coumarin probe are not changed upon irradiation, which is satisfactory for the application required, i.e., in situ synthesis of DNA microarrays.     

Synthesis of amphiphilic polyelectrolyte block copolymers using “living” radical polymerization. Application as stabilizers in emulsion polymerization

This paper describes the synthesis of amphiphilic block copolymers composed of an ionic poly(styrenesulfonate) first segment and a hydrophobic polystyrene second one, using TEMPO-mediated “living” radical polymerization. These copolymers proved to be efficient stabilizers in the emulsion polymerization of styrene.     

Comparative conformational analysis between an undecamer of DNA and its apurinic homologue

Molecular modeling of a DNA undecamer and a corresponding DNA apurinic undecamer (d(CGCACXCACGC) d(GCGTGTGTGCG), X = A or apurinic site) has been performed using the jumna program. Among the possible structures, several are slightly distorted and correctly fit the experimental data obtained from NMR measurements. In these structures, the thymine base that faces the apurinic site lies inside the double helix.     

Reactions of a P-chloro-iminophosphane with main group nucleophiles: Syntheses and x-ray crystal structure analyses of two 1,3-diphosphatetraz-3-ene derivatives

The reactions of chloro(2,4,6-tri-tert-butylphenylimino)phosphane with lithium tris(trimethylsilyl)silanide and lithium diphenylketimide furnish products resulting from the incorporation of a second chloroiminophosphane molecule into the primary substitution product and subsequent nucleophilic displacement of the chlorine ligand. The final products have been characterized by X-ray structure analyses, which revealed some remarkable features.     

Amide‐Based Oligocatenanes by an Iterative Template Strategy

A new pathway for the supramolecular synthesis of oligocatenanes is developed. It is based on a combination of most suitable macrocyclic structural units, obtained from tert‐butyl‐substituted isophthalic acid and terephthalic acid building blocks. These structural parts guarantee, on the one hand, the solubility of the catenanes and their intermediates, and, on the other hand, the preferred formation of larger ring sizes of the macrocycles to be intertwined. Acting as monotopic and ditopic concave templates, the tetra‐ and octalactam macrocycles were submitted to threading procedures to yield higher‐order catenanes of the amide type. By repetition of the threading steps, it was possible to isolate multiply mechanically connected [n]catenanes up to n=4 composed of various macrocyclic units.     

On the role of (weak) compressibility for fluid-structure interaction solvers

In the present study, a weakly compressible formulation of the Navier-Stokes equations is developed and examined for the solution of fluid-structure interaction (FSI) problems. Newtonian viscous fluids under isothermal conditions are considered, and the Murnaghan-Tait equation of state is employed for the evaluation of mass density changes with pressure. A pressure-based approach is adopted to handle the low Mach number regime, ie, the pressure is chosen as primary variable, and the divergence-free condition of the velocity field for incompressible flows is replaced by the continuity equation for compressible flows. The approach is then embedded into a partitioned FSI solver based on a Dirichlet-Neumann coupling scheme. It is analytically demonstrated how this formulation alleviates the constraints of the instability condition of the artificial added mass effect, due to the reduction of the maximal eigenvalue of the so-called added mass operator. The numerical performance is examined on a selection of benchmark problems. In comparison to a fully incompressible solver, a significant reduction of the coupling iterations and the computational time and a notable increase in the relaxation parameter evaluated according to Aitken's Δ² method are observed.