Physical Studies of Hg(II) and Ag(I) DNA Complexes — Theory
The binding of Hg(II) and Ag(I) to the bases of DNA and polynucleotides induces strong absorption and CD bands. From electric dichroism studies, the transition moment of the difference absorption band at 293 nm is in the plane of the bases and has a huge negative CD band at 285 nm; while the corresponding 293 nm difference absorption band of DNA-Ag(I) complex is relatively CD inactive. A second band at 270 nm in the difference absorption spectrum of the DNA-Ag(I) complex has a large associated CD band at 270 nm. This transition is out of the plane of the bases. The increase of the sedimentation coefficients of the rigid rod sonicated DNA by the heavy metal ions can be accounted for by the increase of molecular weight and the decrease of the partial specific volume due to the high density of the heavy metal ions. Either a charge transfer band between the bases and the heavy metal ions or a perturbation theory of the bases by the heavy metal ions would explain satisfactorily the experimental optical results of DNA-Hg(II) and DNA-Ag(I) complexes.
KeywordsCharge Transfer Band Transition Moment Sedimentation Coefficient Dipole Orientation Partial Specific Volume
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