Kinetic and equilibrium studies of the binding of Nickel(II) to 5′-adenosine monophosphate and related compounds

Abstract

Equilibrium studies of the binding of Ni(II) to 5′-AMP have been carried out at 25° and ionic strength I = 0.1 mol 1 −1 (NaClO 4) by ultraviolet spectrophotometry and by potentiometric measurements. The kinetics of this reaction have been studied by the temperature-jump technique. Values of the inverse relaxation time show a nonlinear dependence on reactant concentrations and appear to approach a limiting value at high metal concentrations, implying that complex formation involves more than one substitution step. Equilibrium constant determinations for the reaction of Ni(II) with monohydrogenphosphate and with ribose-5-phosphate reveal weaker binding than with 5′-AMP, indicating that in the 5′-AMP system metal binding to both phosphate and adenine is of importance. With this assumption the kinetic data can be interpreted and analyzed quantitatively. Binding constants and kinetic data are also reported for the reactions of Ni(II) with 3′-AMP and with adenosine.