Understanding B-DNA to A-DNA transition in the right-handed DNA helix: Perspective from a local to global transition.

The right-handed DNA helix exhibits two major conformations, A-DNA and B-DNA, depending on the environmental conditions. The B-DNA to A-DNA (B→A) transition is sequence specific, cooperative, and reversible. The reduced water activity due to the addition of solvents like ethanol or the presence of protein or drug molecules causes B→A transition. In several biological cases, B→A transition occurs at a local level where small fragments of a long DNA sequence undergoes B→A transition. In this review, we have discussed various aspects of B→A transition such as the role of water, sequence specificity, mechanism of B→A transition, etc. The review primarily focuses on the B→A mechanism involved at a local level, and finally its connection to the global transition in theoretical and experimental studies.