Outer Sphere Binding

Study of the CD spectrum of DNA in the presence of Mn(II), Zn(II), and Co(II) indicated that the metal ions induced a B C conformational change. The CD spectra are altered at very low concentrations, and the transformation is considered to occur via reduction of electrostatic repulsive interactions as the cations bind along the phosphate backbone and in the helical grooves [86]. 

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Calculated inter- and intramolecular indirect NMR spin-spin coupling constants and chemical shifts gave predicted values associated with inner- and outer-sphere binding of Mg2+ or Zn2+ to a guanine base.32 NMR spectra (2H, 23Na and 31P) were used to study the interaction of M2+ (=Mg, Cd or Ni) with liquid crystalline NaDNA solutions.33 Ah initio and DFT methods were used to calculate 170 NMR shieldings for OM6(OH)122-, where M = Mg, Ca or Sr.34... 

A further set of complexes that has been shown to interact with DNA by outer sphere binding is of the inert metal—amine type, 2ind these com-... 

Cross linking with Zn(II) and Cu(II) has also been proposed to explain their DNA binding [105, 106]. These base binding examples also underline the point that the increase in which is normally associated with outer sphere binding (neutralization of phosphates) may, for metals, have its origin in a totally different form of binding. 

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