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Polymer self-assembly is a powerful approach for forming nanostructures for solution-phase applications. However, polymer semiconductor assembly has primarily been driven by solvent interactions. Here, we report poly(3-hexythiophene) homopolymer assembly driven and stabilized by oxidative doping with iron (III)

High magnetic field solid-state NMR was performed on amphipathic cationic antimicrobial peptides from fish to characterize their secondary structure and orientation in hydrated phospholipid bilayers. High-resolution distance and orientational restraints on 13C- and 15N-labeled amidated piscidins 1 and 3 provided site-specific information establishing alpha-helicity and an orientation parallel to the membrane surface. Few membrane-bound natural peptides with this topology have been structurally studied at high resolution in the presence of hydrated lipid bilayers. This orientation was foreseen since the partitioning of amphipathic cationic antimicrobial peptides at the water-bilayer interface allows for favorable peptide-lipid interactions, and it may be related to the mechanism of action. The enhanced resolution obtained at 900 MHz evidences a determinant advantage of ultra-high-field NMR for the structural determination of multiple-labeled peptides and proteins.

Les radicaux cationiques de tri- et tetraalkyl cyclopropanes sont generes par transfert d'electron induit par la lumiere a partir du chloranile et du fluoranile. Les effets CIDNP observes au cours de ces reactions sont compatibles avec les radicaux cationiques dans lesquels la liaison cyclopropane la plus substituee est coupee ou affaiblie

Les radicaux cationiques du bicyclo [6.1.0] nonatriene et de ses derives sont generes par transfert d'electrons photoinduit, en solution

A dimer and a mixture of oligomers of acceptor-substituted anilines were prepared, either by Knoevenagel condensation of substituted cyanoacetylpiperazines with p-aminobenzaldehydes or by carbonyldiimidazole-promoted coupling of phenylpiperazines with p-aminocyanocinnamic acids. The resulting oligomeric amidopiperazines possess significantly additive molecular moments when in extended conformations and therefore are potentially valuable for the fabrication of polymer films containing electric field oriented chromophores, such as required for second-order nonlinear optics. The dimer is conformationally defined, and x-ray structural analysis of a model compound confirmed the stereochemistry and bond angles at the amide linkage. The enforced extended conformation of the dimer resulted in an enhanced dipole moment relative to the constituent monomers and raises the possibility of further enhancements in extended higher oligomers.

Reaction photochimique du chloro-6 methylene-5 pentamethyl-1,2,3,4,6 bicyclo [2.2.0] hexene avec le chloranile excite dans l'acetone conduisant au chlorure de pentamethyl benzyle. Mecanisme, transfert d'electron avec mise en jeu de radicaux cationique derives du methylenebicyclo [2.2.0] hexene. Etude par CIDNP

A chemically induced nuclear spin polarization study was made to elucidate the structure of the radical cations of norbornadiene (1) and quadricyclene (2) and to ascertain whether they are two discrete species or a single homallylic structure. Photoreaction of chloranil was used. Results indicate that two discrete radical cations are generated by electron transfer from 1 and 2, and that each must have a lifetime of at least several nanoseconds to explain the generation of nuclear spin polarization. One cation gives rise to a polarized rearrangement product (1) while the other does not lead to a polarized 2. (DLC)

Isomerisation de l'hexamethyl bicyclo [2.2.0] hexadiene-2,5(1) en hexamethylbenzene(2). En solvants polaires conversion de (1) en (2) avec rendements quantiques superieurs a l'unite. Mecanismes radicalaires. Mise en evidence de 2 cations radicalaires differents 2 B 2 et 2 A 1