Complex Formation Equilibria of Unusual Seven-Coordinate Fe(EDTA) Complexes with DNA Constituents and Related Bio-relevant Ligands

Abstract

Seven-coordinate Fe(EDTA)-L complexes, where L represents a DNA constituent (uracil, uridine, thymine, thymidine and inosine), methylamine, ammonium chloride or imidazole, were investigated to resolve the solution chemistry of this system. The results show formation of 1:1 complexes with DNA constituents and the other ligands, supporting the hepta-coordination mode of Fe(III) ion. Stability constants of the complexes were measured by potentiometric titration at 25°C and ionic strength 0.1 mol·L −1 NaNO 3 . The hydrolysis constant of [Fe(EDTA)(H 2 O)] − and the formation constants of the complexes formed in solution were calculated using the non-linear least-squares program MINIQUAD-75. The concentration distributions of the various complex species were evaluated as a function of pH. The thermodynamic parameters H 0 and S 0 , calculated from the temperature dependence of the equilibrium constants, were determined for the Fe(EDTA)-uracil complex. The effect of dioxane as a solvent on the protonation constant of uracil, hydrolysis constants of [Fe(EDTA)(H 2 O)] − , and the formation constants of the Fe(EDTA)-uracil complex are discussed.

Prediction and modeling of pre-analytical sampling errors as a strategy to improve plasma NMR metabolomics data

“…S4 ). While the reason for the decrease in free imidazole levels is not clear, we speculate that binding with Fe-EDTA complexes ( El-Sherif et al , 2012 ), formed by increased extraction from iron containing proteins on prolonged pre-centrifugation delay may be a possible mechanism, since whole blood total concentration of iron is on the level of 7–10 mmol/L, whereas serum iron concentration is only 10–30 µmol/L. In addition, there may be contributions from photolytic degradation ( http://www.inchem.org/documents/sids/sids/288324.pdf ) and increased binding with degraded proteins.…”