Perhaps the most specific biomolecular self-assembly occurs when two single strands of Deoxyribonucleic Acid (DNA) assemble into the infamous double helix. Based on Watson and Crick base pairing, two complimentary strands of DNA will find each other within an enormously complex mixture. Double helical DNA strands can be separated from one another through simple heating, resulting in single stranded DNA (ssDNA). If the solution is allowed to cool, the two strands will re-assemble into a stable double helix. While the Watson and Crick base pairing then allows the specific assembly of the double helix, which is stabilized by relatively strong hydrophobic interactions between the aromatic bases within the center of the helix also known as pi-stacking.

Nanoscientists can take advantage of the double helix's specific stability in numerous ways. One promising approach is to attach single-stranded DNA to small particles that one wishes to assemble. These components could range from diamondoid manifolds to metallic clusters that function as quantum dots. When DNA is used to create functional surfaces, the technique is called DNA Directed Immobilization (DDI). Such patterned surfaces have applications for both nanoelectronic devices and biosensors. Nanogen, a gene chip manufacturer has a versatile method for that takes advantage of DNA's negative charge. By applying a voltage to various parts of a DNA containing solution, the concentrations of DNA over various parts surfaces can be regulated.

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Keywords: self-assembly DNA directed immobilization DDI RNA deoxyribonucleic acid hybridization nanogen concentration gradient gene chip diamondoid nanotechnology double helix pi stacking hydrophobic interactions watson crick base pairing