Helix buckle

The examination of crystallized DNA fragments of varying base composition show sequence-dependent variations in the double helix while emphasizing the A, B and Z forms as structurally distinct families. Variation occurs in the orientation of each base pair to the next by rotation about the X axis or tilt, the Y axis or roll or the Z axis or twist of the helix. Bases in a pair may also rotate in opposition producing variations in buckle, propeller and opening (Fig. 7-5). 

It is exhibited that using Donnell shell and uniform helix deflected shape of CNT simultaneously, leads to incorrect value of the critical angle of twist, conversely Sanders shell model with non uniform helix deflected shape presents correct results of critical twist angle. Besides, Silvestre et al. [42] presented an investigation on linear buckling and postbuckling... 

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