The Complex of Poly(dG) · Poly(dC) with Arginine: Stabilization of the B Form and Transition to Multistranded Structures

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Abstract
We have studied by X-ray diffraction fibers of complexes of poly(dG)·poly(dC) with N-α-acetyl-L-arginine ethylamide. Although these polynucleotides favour the A form of DNA, in this complex it is never found, thus confirming that arginine prevents the appearance of this form of DNA At high relative humidity the B form is present. Upon dehydration two new structures appear. One of them is a triple helix, most likely formed by poly(dC+) · poly(dG) · poly(dC). The other structure found also has features which indicate a multistranded conformation.