Specific Enzyme Immobilization Approaches and Their Application with Nanomaterials

Selective chemical reactions enacted within a cellular environment can be powerful tools for elucidating biological processes or engineering novel interactions. A chemical transformation that permits the selective formation of covalent adducts among richly functionalized biopolymers within a cellular context is presented. A ligation modeled after the Staudinger reaction forms an amide bond by coupling of an azide and a specifically engineered triarylphosphine. Both reactive partners are abiotic and chemically orthogonal to native cellular components. Azides installed within cell surface glycoconjugates by metabolism of a synthetic azidosugar were reacted with a biotinylated triarylphosphine to produce stable cell-surface adducts. The tremendous selectivity of the transformation should permit its execution within a cell's interior, offering new possibilities for probing intracellular interactions.

Renewable biofuels are needed to displace petroleum-derived transport fuels, which contribute to global warming and are of limited availability. Biodiesel and bioethanol are the two potential renewable fuels that have attracted the most attention. As demonstrated here, biodiesel and bioethanol produced from agricultural crops using existing methods cannot sustainably replace fossil-based transport fuels, but there is an alternative. Biodiesel from microalgae seems to be the only renewable biofuel that has the potential to completely displace petroleum-derived transport fuels without adversely affecting supply of food and other crop products. Most productive oil crops, such as oil palm, do not come close to microalgae in being able to sustainably provide the necessary amounts of biodiesel. Similarly, bioethanol from sugarcane is no match for microalgal biodiesel.

A simple technique has been devised that allows the direct synthesis of native backbone proteins of moderate size. Chemoselective reaction of two unprotected peptide segments gives an initial thioester-linked species. Spontaneous rearrangement of this transient intermediate yields a full-length product with a native peptide bond at the ligation site. The utility of native chemical ligation was demonstrated by the one-step preparation of a cytokine containing multiple disulfides. The polypeptide ligation product was folded and oxidized to form the native disulfide-containing protein molecule. Native chemical ligation is an important step toward the general application of chemistry to proteins.