Proteoglycans and their constituent glycosaminoglycans are associated with all amyloid deposits and may be involved in the amyloidogenic pathway. In Alzheimer's disease, plaques are composed of the amyloid-b peptide and are associated with at least four different proteoglycans. Using CD spectroscopy, fluorescence spectroscopy and electron microscopy, we examined glycosaminoglycan interaction with the amyloid-b peptides 1±40 (Ab40) and 1±42 (Ab42) to determine the effects on peptide conformation and fibril formation. Monomeric amyloid-b peptides in trifluoroethanol, when diluted in aqueous buffer, undergo a slow random to amyloidogenic b sheet transition. In the presence of heparin, heparan sulfate, keratan sulfate or chondroitin sulfates, this transition was accelerated with Ab42 rapidly adopting a b-sheet conformation. This was accompanied by the appearance of well-defined amyloid fibrils indicating an enhanced nucleation of Ab42. Incubation of preformed Ab42 fibrils with glycosaminoglycans resulted in extensive lateral aggregation and precipitation of the fibrils. The glycosaminoglycans differed in their relative activities with the chondroitin sulfates producing the most pronounced effects. The less amyloidogenic Ab40 isoform did not show an immediate structural transition that was dependent upon the shielding effect by the phosphate counter ion. Removal or substitution of phosphate resulted in similar glycosaminoglycan-induced conformational and aggregation changes. These findings clearly demonstrate that glycosaminoglycans act at the earliest stage of fibril formation, namely amyloid-b nucleation, and are not simply involved in the lateral aggregation of preformed fibrils or nonspecific adhesion to plaques. The identification of a structure±activity relationship between amyloid-b and the different glycosaminoglycans, as well as the condition dependence for glycosaminoglycan binding, are important for the successful development and evaluation of glycosaminoglycan-specific therapeutic interventions.

This article reports for the first time a novel category of hollow organic@inorganic hybrid two‐layered nanoparticles (NPs), in which the inner layer is formed by optically active helical polyacetylene, and the outer layer by silica. Such NPs show remarkable optical activity and are successfully used for enantioselective crystallization. To prepare such NPs, n‐butyl acrylate undergoes radical polymerization to first form poly(n‐butyl acrylate) (PBA) cores two shells by catalytic polymerization of substituted acetylene and sol–gel approach of TEOS (tetraethyl orthosilicate), respectively. Removal of the PBA cores provides the expected hollow core/shell NPs. The intense dircular dichroism (CD) effects demonstrate that the hollow chiral NPs possess considerable optical activity, arising from the helical substituted polyacetylenes forming the inner layer. The hollow NPs are further used as chiral templates to induce enantioselective crystallization of racemic alanines, demonstrating the significant potential applications of the hollow chiral NPs in chiral technologies. Also of particular significance is the detailed process of the induced crystallization observed by TEM. The strategy for preparing the hollow hybrid chiral NPs should be highlighted since it combines free radical polymerization and catalytic polymerization with sol–gel process in a single system, by which numerous advanced materials will be accessible.

The research in circularly polarized luminescence has attracted wide interest in recent years. Efforts on one side are directed toward the development of chiral materials with both high luminescence efficiency and dissymmetry factors, and on the other side, are focused on the exploitations of these materials in optoelectronic applications. This review summarizes the recent frontiers (mostly within five years) in the research in circularly polarized luminescence, including the development of chiral emissive materials based on organic small molecules, compounds with aggregation-induced emissions, supramolecular assemblies, liquid crystals and liquids, polymers, metal-ligand coordination complexes and assemblies, metal clusters, inorganic nanomaterials, and photon upconversion systems. In addition, recent applications of related materials in organic light-emitting devices, circularly polarized light detectors, and organic lasers and displays are also discussed.

No abstract

Circularly polarized luminescent (CPL) materials are currently drawing ever-increasing interest. This contribution reports the first success in simply combining chiral helical substituted polyacetylenes (HSPAs) with achiral luminophores to fabricate CPL materials demonstrating a high dissymmetry factor (g lum ) up to 10 −1 , despite neither covalent nor noncovalent interactions occurring between the two components. Circularly polarized scattering and fluorescence-selective absorption mechanisms are proposed for the generation of CPL, and a "matching rule" is further established for selecting chiral polymers and achiral luminophores for the purpose. Taking advantage of the circularly polarized scattering effect, full-color tunable CPL materials are prepared from the combination of achiral fluorescent dyes and chiral HSPAs. Following the fluorescence-selective absorption mechanism, functional composite films with on−off and switchable CPL performance are fabricated. Also, remarkably, the g lum value in the prepared materials can reach up to +0.323. The present study provides a simple, powerful, and universal strategy for constructing novel CPL materials.