Biomedical Engineering Reference
In-Depth Information
Fig. 1
Basic features of dsDNA
10%indryweight,andtheDNAcanbeextractedfromsalmonmiltbyavery
simple process. World production of salmon has increased to over 2.4 million
tons in 2004. Based on this catch amount, it is estimated that about 3000 tons
of DNA can be obtained every year just from the salmon supply. Such facile
sources of DNA effectively promoted research of DNA-based materials for use
in further applications.
According to the Watson-Crick model, a DNA molecule consists of two
polynucleotide strands coiled around each other in a helical fashion, which
is often described as a double helix. Each strand has a backbone made up
of sugar molecules linked together by phosphate groups. The orientation of
the two strands is antiparallel. The backbone of double-stranded DNA (ds-
DNA) is highly negatively charged. The two negatively charged backbones
lead to DNA “stiffness”, with a persistence length of around 50 nm, which
corresponds to 150 base pairs in the double helix [1]. This property allows
dsDNA to form highly ordered complexes with electrostatic binding agents
such as metal ions, cationic surfactants, and polycationic agents. The reports
selected relating to DNA electrostatic binding will be detailed in Sect. 2 on
helical anionic polymers.
The opposite strands of dsDNA are held in precise register by regular base
pairing between the two strands. This base-pair complementarity is a conse-
quence of the size, shape, and chemical composition of the bases. The highly
specific A-T and G-C Watson-Crick hydrogen bonding provides the chemical
foundation for genetics. This structurally well-defined cohesive combining
of DNA stands has been tried in nanotechnology to direct the assembly of
highly structured materials with specific nanoscale features. Section 3 on
DNA strand pairing will give an overview on DNA nanoarchitectures such as
self-assemble structure, DNA arrays, and DNA nanomechanical devices.
The 3D structure of DNA is known in detail and this has permitted the
meaningful structural and mechanistic interpretation of DNA-agent com-
plexes. Two right-handed antiparallel double helix forms of DNA are well
