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1 2008

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Study on Coordination and Noncovalent Interactions in Cu(II), L-Aspartic acid and Adenosine-5'-monophosphate Systems

Bregier-Jarzebowska R., Gasowska A., Abd El-Latif S. T.

Polish Journal of Chemistry

2008

Vol. 82, nr 11

2057-2065

In the L-aspartic acid (Asp) and adenosine-5c-monophosphate (AMP) systems molecular complexes (Asp)Hx(AMP) are formed as a result of noncovalent dipole-ion interactions between Asp and AMP. Stability constants of particular species has been determined and the interaction centres have been identified as the deprotonated carboxyl groups and the amine group from Asp along with the phosphate group and endocyclic nitrogen atoms from AMP. At pH close to 7 an inversion in the character of the interactions takes place: in an acidic medium the N(1)H group from AMP is a positive reaction centre, while in a basic medium after deprotonation it becomes a negative reaction centre. In the ternary system of Cu(II)/Asp/AMP the formation of protonated complexes of the type Cu(Asp)Hx(AMP), heteroligand complex Cu(Asp)(AMP) and hydroxocomplex Cu(Asp)(AMP)(OH) have been observed to form. The modes of coordination have been established on the basis of the spectroscopic data and equilibrium studies. At low pH the introduction of copper(II) ions to the binary system does not change the sites of intermolecular noncovalent interactions of the bioligands. Start ing from pH near 4, the presence of Cu(II) ions totally eliminates the noncovalent interactions between bioligands observed in the Asp/AMP binary systems.