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A calorimetric study of the Ni(II)-5' AMP system. A base-stacking stabilization
L A Herrero1, A M Calafat, A Terrón
1Department of Chemistry, Universitat de les Illes Balears, Palma de Mallorca, Spain.
European Journal of Biochemistry
|December 5, 1991
Summary
Nickel(II) ions interact with 5'-adenosine monophosphate (5'-AMP) in solution. Calorimetry reveals thermodynamic parameters supporting the formation of a Ni(5'-AMP)2 complex, likely via purine ring stacking.
Area of Science:
- Coordination Chemistry
- Biophysical Chemistry
- Thermodynamics
Background:
- Metal ions play crucial roles in biological systems, often interacting with nucleotides.
- Understanding these interactions is vital for elucidating biochemical processes and designing therapeutic agents.
- Nickel(II) is a biologically relevant metal ion with known interactions with nucleic acid components.
Purpose of the Study:
- To determine the thermodynamic parameters governing the interaction between Ni(II) and 5 acronym{'-AMP) in aqueous solution.
- To investigate the stoichiometry and stability of the formed complexes.
- To explore the structural basis of the interaction, specifically the role of purine ring stacking.
Main Methods:
- Isothermal titration calorimetry (ITC) was employed to measure binding enthalpies and affinities.
- Experiments were conducted in aqueous solution at a controlled ionic strength (0.1 M tetramethylammonium bromide) and temperature (25°C).
- Physiological pH was maintained to mimic biological conditions, and conditions were optimized to prevent polynuclear complex formation.
Main Results:
- The formation constants for Ni(5 acronym{'-AMP) (logK1 = 2.55) and Ni(5 acronym{'-AMP)2 (logK2 = 2.34) were determined.
- The enthalpies of complex formation were found to be ΔH1 = -10.0 kJ/mol for Ni(5 acronym{'-AMP) and ΔH2 = 21.6 kJ/mol for Ni(5 acronym{'-AMP)2.
- These thermodynamic data confirm the formation of the Ni(5 acronym{'-AMP)2 complex and support the proposed 'stacking' interaction between the purine rings, facilitated by Ni(II).
Conclusions:
- The Ni(II)-5 acronym{'-AMP) interaction proceeds through defined steps, forming both ML and ML2 complexes.
- The thermodynamic profile, particularly the enthalpy changes, provides evidence for the proposed purine ring stacking mechanism.
- The findings contribute to the understanding of metal-nucleotide interactions in biological contexts.
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