A multi-O\u3csub\u3e2\u3c/sub\u3e complex derived from a copper(I) dendrimer

\u3cp\u3eThe high-pressure reaction of 2-vinylpyridine with the primary amines of four consecutive generations of poly(propylene imine) dendrimers (DAB-dendr- (NH\u3csub\u3e2\u3c/sub\u3e)(n)) (n = 4, 8, 16, 32) yielded dendrimers with bis[2-(2- pyridyl)ethyl]-amine (PY2) ligands. The complexation of the new dendrimers with metal ions was investigated by a variety of techniques. The reaction of the first- and fourth-generation dendrimers (n=4 and 32, respectively) with Zn(II)(ClO\u3csub\u3e4\u3c/sub\u3e)\u3csub\u3e2\u3c/sub\u3e was studied by \u3csup\u3e1\u3c/sup\u3eH NMR titration, and the complexation of all new dendrimers with Cu(II)(ClO\u3csub\u3e4\u3c/sub\u3e)\u3csub\u3e2\u3c/sub\u3e was investigated by UV/Vis and EPR spectroscopy. Quantitative coordination of one metal ion per PY2 group was demonstrated in all cases. A UV/Vis titration of the fourth-generation dendrimer DAB-dendr-(PY2)\u3csub\u3e32\u3c/sub\u3e in dichloromethane with [Cu(I)(CH\u3csub\u3e3\u3c/sub\u3eCN)\u3csub\u3e4\u3c/sub\u3e](ClO\u3csub\u3e4\u3c/sub\u3e) in acetonitrile revealed that approximately 30 Cu(I) ions were bound. Low-temperature UV/Vis spectroscopy of this complex in dichloromethane at -85°C in the presence of dioxygen showed that approximately 60-70% of the copper centers can bind dioxygen, corresponding to 10-11 of these molecules per dendrimer molecule. This complex can be considered a synthetic analogue of hemocyanin, the copper-containing oxygen transport protein from the hemolymph of molluscs and arthropods.\u3c/p\u3

Dendrimer-based hydroxyapatite composites with remarkable materials properties

No abstract

Chiral discotics; expression and amplification of chirality

In this contribution, chirality and discotic liquid crystals are discussed as a tool for studying the self-assembly of these molecules, both in solution and in the solid state. Therefore, the objective of this chapter is to summarize and elucidate how molecular chirality can be expressed in discotic supramolecular architectures both in the liquid crystalline state and in solution. Closely related to this issue is the question how chirality can be amplified from one discotic molecule to another, a phenomenon that has mainly been studied in solution, but can have significant impact on the issue of the origin of chirality. The different mesophase assemblies of chiral discotics are presented. Supramolecular assemblies of discotic molecules in solution, although they have not yet found application, allow for a detailed and specific investigation of the interactions that are required to express chirality at higher levels of organization. As such, the fundamental knowledge acquired from supramolecular assemblies in solution might formulate the design criteria for chiral discotic mesophases and provide the necessary tools for the creation of functional systems

MIXED MONOLAYERS AND MULTILAYERS OF POLY(ISOCYANIDE)S WITH NONLINEAR OPTICALLY-ACTIVE SIDE-CHAINS

The properties and structure of Langmuir-Blodgett mono- and multilayers of several poly(isocyanide)s with non-linear optically active side-chains were studied. These polymers formed very rigid layers or layers which appeared to be unstable. To circumvent this problem they were mixed with other poly(isocyanide)s or with amylose-butyrate. Transmission electron microscopy studies of the polymeric mixtures revealed that phase separation occurred in all cases and that only poly(isocyanide)s substituted with hydrophilic side chains formed monomolecular layers. Depending on the nature of the polymer which was used for mixing, the dye polymers could be deposited with Y- or Z-type transfer. Second-harmonic intensities generated from these films were small in the case of the Y-type multilayered films and moderately high in the case of the Z-type films.</p

Sortase a-mediated n-terminal modification of cowpea chlorotic mottle virus for highly efficient cargo loading

\u3cp\u3eA new strategy is described for the modification of CCMV for loading of cargoes inside the viral capsid. Sortase A, an enzyme which is present in Gram-positive bacteria, was used to attach cargo to the glycine-tagged N-termini of several CCMV variants. We show that small molecules and proteins bearing a C-terminal LPETG-motif can be attached in this way. This method allows for the site-specific, covalent, and orthogonal modification of CCMV capsids in a mild fashion, leading to high encapsulation efficiencies. This strategy can easily be expanded to other types of cargoes, labeled with an LPETG-tag without altering protein function.\u3c/p\u3