Studies of Fe(II) and Fe(III)-DNA complexes by XANES spectroscopy

The composition of the ligands around the iron centers in Fe(II) and Fe(III )-DNA complexes has been investigated by X-ray Absorption Near Edge Structu re (XANES) spectroscopy at the Fe-K-edge. The spectra are compared to the m odels FePO4 and Fe(dadipy)(2), each one bearing only one of the ligands exp ected in the Fe-DNA interaction, namely oxygen (from phosphate groups, H2O or bases) and nitrogen (from bases), respectively. The spectrum of Fe(II)-D NA exhibits a higher pre-edge peak and a more prominent shoulder at 7145 eV than Fe(III)-DNA. These spectral features indicate a distortion associated with the the presence of nitrogen in the first coordination sphere Fe(II)- DNA. These spectral features indicate a distortion associated with the pres ence of nitrogen in the first coordenation sphere of Fe(II)DNA. Similaritie s between Fe(III)-DNA and FePO4 are consistent with the possibility that on ly oxygen atoms are coordinated to the Fe(III) center.