The dynamics of Fe-57 nuclei in Fe-II-DNA and [Fe-II(1-methyl-2-mercaptoimidazole)(2)]-DNA condensates

摘要

Alcoholic solutions of FeCl2 and Fe-II(Hmmi)(2)Cl-2 (Hmmi=1-methyl-2-mercaptoimidazole) induce calf thymus DNA condensation from aqueous solutions buffered at pH 7.4. A 1:1 Fe-II-(DNA monomer) stoichiometry is assumed. The Fe-57 Mossbauer hyperfine parameters suggest an octahedral coordination environment, severely distorted, in both Fe-II-(DNA monomer) and [Fe-II(Hmmi)(2)]-(DNA monomer) condensates. The dynamic properties of iron nuclei in freeze-dried samples were investigated by means of variable temperature Fe-57 Mossbauer spectroscopy. Mean square displacements, (x(2))(T), were calculated, such as the effective vibrating mass and the Mossbauer lattice temperature of the solids. (x(2)) increases linearly with the temperature in the whole temperature range explored; the absolute values are typical for lattice or solid-state vibrations. Very similar values for the effective vibrating masses were extracted, suggesting comparable covalency of the bonding interaction between the metal atom and its ligands, while the Mossbauer lattice temperatures show a softening of the lattice for [Fe-II(Hmmi)(2)]-(DNA monomer) with respect to Fe-II-(DNA monomer) condensate.