Backbone geometry of oriented DNA fibers as revealed by 31P chemical shielding anisotropy.

Since the 31P solid state NMR is concerned only with information on the phosphodiester orientations of DNA, the data from DNA fibers do not provide information about helical parameters such as the pitch and axial rise/residue. However, the method is extremely useful to elucidate the backbone conformations of DNA, especially under hydrated conditions where the X-ray fiber diffraction method cannot reveal much about structural details like multiplicity of the backbone conformations. It was shown that the conformation of the A family of DNA is rather restricted within a limited range, whereas multiple conformations generally exist in the B family of DNA fibers. The appearance of the structural multiplicity in DNA fibers under hydrated conditions suggests the important roles of the structure of DNA in gene regulation.