Conformationalflexibility of DNA: Polymorphism and handness

Abstract

Observation of both right- and left-helical DNA fragments in the single crystals and different poly morphous forms of DNA in fibres suggest that the con formational flexibility is inherent in the DNA mole cule. However, the limited number of DNA fragments solved at atomic resolution and poorly resolved fibre data do not enable us to understand the precise stereo chemical nature of the conformational flexibility of DNA and its role in determining the three-dimensional structure. Thus, a theoretical study on the confor mational flexibility of DNA is called for. The pre sent thesis studies the conformational flexibility of DNA in precise stereochemical details and its role in deciding the three-dimensional structure with special reference to DNA polymers in fibres. It is concluded that DNA in either handedness is a natural outcome of the conformational flexibility inherent in the molecule. It is also pointed out that the same flexibility can be used to make a stable link between' right- and left-helical DNA fragments and this results in an RL model — a viable alternative to the classical right-handed double-helix of DNA.