DNA exists in a lot of likely conformations that comprise A DNA, B DNA, and Z DNA forms even though only B-DNA and Z-DNA have been straight experiential in functional organisms. The conformation that DNA adopts depends on the hydration level DNA sequence, the quantity and direction of super coiling, chemical modifications of the bases, the type and concentration of metal ions, as well as the presence of polyamines in solution.
The first published reports of A-DNA X-ray diffraction patterns and also B-DNA used analyses based on Patterson transforms that provided only a limited amount of structural information for oriented fibers of DNA. An alternate analysis was then proposed by Wilkins et al, in 1953, for the in vivo B-DNA X-ray diffraction/scattering patterns of highly hydrated DNA fibers in terms of squares of Bessel functions. In the same periodical, James D. Watson and Francis Crick presented their molecular modeling psychoanalysis of the DNA X-ray diffraction patterns to suggest that the structure was a double-helix.
