NaDNA-bipyridyl-(ethylenediamine)platium (II) complex: Structure in oriented wet-spun films and fibers

Complexes of NaDNA with bipyridyl-(ethylenediamine)platinum(II) (abbreviate d [(bipy)Pt(en)(2+)) in solid, oriented films, prepared with a wet-spinning method, have been studied using x-ray diffraction, elastic neutron scatter ing, two-dimensional magic-angle-spinning nuclear magnetic resonance (NMR), infrared (IR) linear dichroism, and IR absorption. All of these experiment s indicate that the DNA in this complex is in the B conformation. The neutr on diffraction experiments reveal that the rise per residue is 3.31 Angstro m, indicating that the [(bipy)Pt(en)](2+) molecular ion causes a small dist ortion of the B conformation. The neutron data in the direction perpendicul ar to the helical axis are consistent with a centered orthorhombic unit cel l with a = 22.65 Angstrom and b = 32.2 Angstrom. The NMR and IR experiments show that the orientation of phosphate groups in the DNA[(bipy)Pt(en)](2+) complex is the same as that observed for pure DNA in the B conformation. T he IR experiments also show that the [(bipy)Pt(en)](2+) molecular ion stabi lizes the B conformation of DNA down to 59% relative humidity, a low water activity. Mechanochemical experiments on wet-spun NaDNA fibers in 68% ethan ol with and without [(bipy)Pt(en)](2+) reveal a 9% elongation of the DNA fi bers as the complex is formed.