FIGURE 2-13 Reciprocal exhange of DNA, an idea Seeman “stole” from nature to create new DNA motifs. The blue and red lines represent two different sequences of DNA. After reciprocal exchange, the blue strand and red strand bedcome red and blue strands.

SOURCE: Nadrian Seeman, presentation slides.

structures more diverse than the natural DNA double helix, Seeman says he stole the idea of DNA and reciprocal exchange from nature (Seeman, 2001). He added “some people use the term bioinspired; I use the term biokleptic.” Figure 2-13 shows a simplistic illustration of reciprocal exchange, where two different DNA sequences combine to produce new structures.

Branched species can then be connected to one another using the same interactions that genetic engineers use to produce constructs, that is, cohesion by molecules tailed in complementary single-stranded overhangs known as “sticky ends.” Such sticky-ended cohesion is used to produce N-connected objects, crystalline lattices, and complex nanomechanical devices such as assembly lines.

The objectives and applications in Seeman’s laboratory include architectural control and scaffolding, producing nanomechanical devices such as nanorobotics and nanofabrication, and self-replicable systems (Gu et al., 2010). Seeman said his lab focuses on DNA because “nucleic acid sequences can be programmed and synthesized, leading to information-based structural, dynamic, and catalytic chemistry.”

As illustrated in Figure 2-14, the intellectual goal of structural DNA nanotechnology is to control the structure of matter in three dimensions (3D) to the highest extent possible and to understand the connection between the molecular and macroscopic scales (Zheng et al., 2009). Seeman said that the ability to control matter in this way has the potential to open new functionality of relevance to energy and other applications. For example, as discussed during the workshop, the 3D lattice structures Seeman created could have applications for separations or storage of small proteins or other molecules.

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