Figure 13

Two-dimensional DNA arrays. (A) Schematic drawings of DNA double crossover (DX) units. In the meiotic DX recombination intermediate, labeled MDX, a pair of homologous chromosomes, each consisting of two DNA strands, align and crossover in order to swap equivalent portions of genetic information; ‘HJ’ indicates the Holliday junctions. The structure of an analogue unit (ADX), used as a tiling unit in the construction of DNA two-dimensional arrays, comprises two red strands, two blue crossover strands and a central green crossover strand. (B) The strand structure and base pairing of the analogue ADX molecule, labeled A, and a variant, labeled B*. B* contains an extra DNA domain extending from the central green strand that, in practice, protrudes roughly perpendicular to the plane of the rest of the DX molecule. (C) Schematic representations of A and B* where the perpendicular domain of B* is represented as a blue circle. The complementary ends of the ADX molecules are represented as geometrical shapes to illustrate how they fit together when they self-assemble. The dimensions of the resulting tiles are about 4 × 16 nm and are joined together so that the B* protrusions lie about 32 nm apart. (D) The B* protrusions are visible as ‘stripes’ in tiled DNA arrays under an atomic force microscope. (Reprinted with permission from Reference [142]. Copyright 2003 Macmillan Publishers Ltd.)