The properties of DNA can be classified in mainly three different levels: the sequence, the structure, and the folding pathway. The composition or the sequence of DNA based on only four nucleotides, namely adenine (A), thymine, guanine, and cytosine, lays the basis for the primary structure, which also largely determines the secondary and tertiary structures of DNA. The complementarity underlying Watson-Crick base-pairing of A:T and G:C and the stacking forces leads to the classical double helical structure as well as other forms of secondary DNA structures (e.g., A and Z form of DNA). Watson-Crick base-paring is intricately orchestrated by a number of week forces, including hydrogen bonding, π-stacking, electrostatic forces, and hydrophobic effect. It also offers foundation for molecular recognition of DNA.

Double stranded DNA is capable of self-folding into complex structures, enabling it to locomote and respond to the environment. These three levels of structures give rise to some interesting and useful features or attributes. DNA is a water-soluble macromolecule, and synthetic DNA displayed good biocompatibility. It is generally stable under physiological conditions, but can be hydrolyzed by acid and alkali when pH changes. At the same time, DNA is a highly charged polymer mostly due to the phosphate group in the nucleotides. The flexibility of single-stranded DNA (sand) and the relatively weak bonding between base pairs of duplex DNA allows interacting DNA strands to seek thermodynamically favored configurations, making possible programmed self-assembly of complex structures. G:C base-pair is more stable than A:C one due to the stronger hydrogen bond present, thus GC content markedly influence DNA properties. DNA can be cleaved primarily based on three ways: hydrolysis, photochemistry and oxidative reactions. In the natural living systems, hydrolysis is the primary mechanism. These mechanisms allow for different approaches in degradation of the DNA based materials or ways of protecting these materials from attacks. For example, in designing DNA only or DNA cross-linked macro-materials, the sequence of the DNA can be chosen in a way that it would be protected under physiological conditions while degraded upon pathological concentration releasing encapsulated therapeutic agents.

DNA is susceptible to modification including cleavage and chemical deletion or addition by a large number of enzymes. Nature has created a rather delicate and precise machinery to manipulate, such as cutting, ligating, unwinding, folding, synthesizing, initiating, modifying, and deleting, DNA in vivo. Many of the enzymes involved in the process have been identified, namely, restriction enzymes, ligase, helicase, gyrate, polymerase, primate, proofreading exonuclease, and a host of other enzymes. Double stranded DNA is semi-flexible and can possess high rigidity. Upon based pairing, and DNA strands can be straightened, which underlies the design of a nano-actuator. Previous studies on DNA mechanics suggest that DNA strands can be considered as rigid rods with tensile modulus of hundreds of MPa when the force applied is below certain threshold, and this leads to a smaller possibility of stretching DNA longitudinally.. Meanwhile, the energy to bend a DNA strand is inversely correlated to its length. It is emphasized here that as the earlier work pointed out, the physical properties of DNA are closely tied to its biological functions.

Thanks & Regards,
Nicola B
Editorial Team
Journal of Biochemistry & Biotechnology