Self-assembly of enzymes on DNA scaffolds: en route to biocatalytic cascades and the synthesis of metallic nanowires.

DNA strands consisting of programmed sequence-specific domains were synthesized by the rolling circle amplification (RCA) process. The spatial positioning of glucose oxidase (GOx) and of horseradish peroxidase (HRP) on the RCA-synthesized DNA template via hybridization enabled the activation of the bienzyme cascade. The GOx-catalyzed oxidation of glucose yielded gluconic acid and H(2)O(2), and the resulting H(2)O(2) oxidized 2,2'-azino-bis[3-ethylbenzthiazoline-6-sulfonic-acid] (ABTS(2-)) in the presence of HRP. The enzyme cascade could not be activated in the absence of the organizing DNA template or in the presence of a foreign DNA. Also, Au NPs-functionalized GOx was hybridized with the RCA-synthesized single-stranded DNA. The biocatalytic growth of the NPs through the oxidation of glucose, in the presence of AuCl(4)(-), enabled the synthesis of 1-5 microm long Au wires, exhibiting a width of ca. 150 nm.