Self-Association, Protonation, and Metal-Coordination of 1,N6 - Ethenoadenine Derivatives in Comparison with Their Parent Compounds Adenosine, AMP and ATP

Abstract

Since X-ray structure determinations of enzyme-substrate complexes are rare and not easily obtained, the use of so-called molecular probes has become popular. 1,N⁶-ethenoadenine derivatives are often employed as such to substitute for adenine substrates due to their excellent fluorescent properties. By using these derivatives as an example, it is shown that a seemingly small alteration, namely the insertion of the 1,N⁶-etheno-bridge into the adenine moiety, which may appear from an «organic» point of view as very satisfying, can drastically alter the metal ion-coordinating properties. As metal ions are essential to biological phosphoryl and nucleotidyl transfer, it is important to be aware of these changes; in fact, great care should be exercised in employing 1,N⁶-ethenoadenine derivatives as probes for adenine substrates in the presence of metal ions: the stabilities and structures of the corresponding complexes in solution are often rather different.