Dispersion and surface functionalization of oxide nanoparticles for transparent photocatalytic and UV-protecting coatings and sunscreens.

This review describes recent efforts on the synthesis, dispersion and surface functionalization of the three dominating oxide nanoparticles used for photocatalytic, UV-blocking and sunscreen applications: titania, zinc oxide, and ceria. The gas phase and liquid phase synthesis is described briefly and examples are given of how weakly aggregated photocatalytic or UV-absorbing oxide nanoparticles with different composition, morphology and size can be generated. The principles of deagglomeration are reviewed and the specific challenges for nanoparticles highlighted. The stabilization of oxide nanoparticles in both aqueous and non-aqueous media requires a good understanding of the magnitude of the interparticle forces and the surface chemistry of the materials. Quantitative estimates of the Hamaker constants in various media and measurements of the isoelectric points for the different oxide nanoparticles are presented together with an overview of different additives used to prepare stable dispersions. The structural and chemical requirements and the various routes to produce transparent photocatalytic and nanoparticle-based UV-protecting coatings, and UV-blocking sunscreens are described and discussed.

Supported metalloporphyrin catalysts for alkene epoxidation.

This review is devoted to the recent advances in the preparation of immobilised metalloporphyrins and their use as heterogeneous catalysts for alkene epoxidation. The wide range of supports, nature of attachments, and metalloporphyrins that have been reported is detailed and a comparison is made between the activities of the resulting catalysts in the epoxidation of different alkenes. The important issue of recyclability of the metalloporphyrins is also covered.

Polymer-supported manganese porphyrin catalysts--peptide-linker promoted chemoselectivity.

Manganese porphyrin catalysts were tethered to polymer-supports via peptide linkers. The reactivity and chemoselectivity of the catalysts were assessed in the epoxidation of limonene. It was found that the inclusion of a peptide linker incorporating a donor heteroatom which could act as an axial ligand led to a supported manganese porphyrin catalyst with unprecedented selectivity and stability.

Recycling and reuse of a polymer-supported scavenger for amine sequestration.

The regeneration and reuse of a supported scavenger 1 for amine sequestration has been achieved up to three times without significant loss of activity. The scavenging process between the aldehyde resin 1 and a range of amines has been investigated in detail to determine the scope of this scavenger. Its application for the rapid purification of a small library of secondary amines 7a-j has also been demonstrated, and it has been shown that the large excess of scavenger resin used can be recovered and recycled, making this a more cost-effective process.

An iron-sulfur cluster in the family 4 uracil-DNA glycosylases.

The 25-kDa Family 4 uracil-DNA glycosylase (UDG) from Pyrobaculum aerophilum has been expressed and purified in large quantities for structural analysis. In the process we observed it to be colored and subsequently found that it contained iron. Here we demonstrate that P. aerophilum UDG has an iron-sulfur center with the EPR characteristics typical of a 4Fe4S high potential iron protein. Interestingly, it does not share any sequence similarity with the classic iron-sulfur proteins, although four cysteines (which are strongly conserved in the thermophilic members of Family 4 UDGs) may represent the metal coordinating residues. The conservation of these residues in other members of the family suggest that 4Fe4S clusters are a common feature. Although 4Fe4S clusters have been observed previously in Nth/MutY DNA repair enzymes, this is the first observation of such a feature in the UDG structural superfamily. Similar to the Nth/MutY enzymes, the Family 4 UDG centers probably play a structural rather than a catalytic role.