ABSTRACT

Form Toroids? ............................................................................................. 233 10.5 Particle Aggregation.................................................................................... 235 10.6 Summary and Implications for Bionanotechnology................................... 238 References............................................................................................................. 239

Although DNA is celebrated for its properties of chemical recognition, which make it the perfect vehicle for storage and propagation of genetic instructions, its nonsequence-specific properties are much less familiar. DNA possesses closely spaced backbone phosphates, which define it as a strongly anionic polyelectrolyte. It is this polyelectrolyte character which dominates its non-sequence-specific behavior, and gives rise to some unusual motifs of self-assembly: at very low concentrations and in solutions of very low ionic strength, DNA can form large, disperse and delicate, yet highly ordered “rafts”;1-3 at high concentrations and in the presence of high amounts of salt, DNA assumes various classic forms of liquid crystals;4-8 and, as will be reviewed in this chapter, at intermediate concentrations and presence of moderate salt, charge-neutralized DNA forms nanometer-scale, toroidal-shaped particles in which the DNA is packed in a dense, crystal-like manner.