ABSTRACT
The development and function of almost all known living organisms contain the traits of genetic information, carried by deoxyribonucleic acid (DNA). Along with RNA and proteins, DNA serves as the building block of life. In addition to central function as the wellknown genetic information reservoir, the remarkable self-assembly characteristics make DNA probably one of the most promising biomolecules for the elds of material science, molecular computing, (bio)analysis, and nanotechnology. DNA is composed of a long chain of components called nucleotides, the two purine bases, adenine (A) and guanine (G), and the two pyrimidine bases, cytosine (C) and thymine (T). The sequence of the bases determines the structure and function of the nucleic acid strands. The extremely precise base-pairing rules of A-T and C-G, resulting from the cooperative interplay of hydrogen bonding, π-stacking, electrostatic and hydrophobic interactions, drives one DNA strand to assemble with its complementary strand into a double-helix. The strands rich in G or C bases can be triggered by environmental stimuli to self assemble into intermolecular or intramolecular G-quaruplex (Keniry 2001) or C-quadruplex (i-motif) structures (Liu et al. 2009a). Coordination interaction may bridge the specic bases in the presence of the corresponding metal ions, such as T-Hg2+-T or C-Ag+-C, to induce DNA motifs (Clever et al. 2007). Alternatively, the chelation between specic sequence and metal ions could create heterocycles into the DNA scaffold, by bridging the nucleic acid strands (Liu et al. 2009b). The diverse structural patterns of DNA allow for programmed assembly of one-, two-, threedimensional (1D, 2D, and 3D, respectively), or any deliberately designed structures, using the encoded information in the nucleic strands. On the other hand, the function of DNA is sequence-dependent. The systematic evolution of ligands by exponential enrichment (SELEX) process has selected nucleic acids that specically bind low molecular weight substrate or proteins (aptamers) (Cho et al. 2009; Liu et al. 2009b) and an in vitro selection technique has been developed to obtain DNAzymes (or deoxyribozymes) that catalyze reactions in the presence of particular metal ions (Liu et al. 2009b; Wilner et al. 2012). Furthermore, DNA strands were evolved into the aptamer like the apoenzymes in protein peroxidase (Travascio et al. 1998). Once binding to hemin (iron(III)-protoporphyrin), the G-rich DNA aptamar-hemin complex could enhance the low intrinsic peroxidatic activity of hemin. The attractive structural and functional features of DNA predict the variability and complexity of DNA nanostructures and pave the way to develop DNA nanotechnology that specializes in the design and manufacture of articial nucleic acid structures for technological uses (Figure 16.1).
