Models for enzyme-copper-nucleic acid interaction: Interaction of some biomimetic copper complexes derived from salicylaldehyde, glycine and ɑ-alanine with adenine and adenosine

Abstract

The interaction of [CuL(H₂O)] (H₂L = salicylideneglycine or salicylidene-ɑ-alanine) with adenine and adenosine has been investigated using UV-VIS, IR and EPR spectral and electrochemical techniques. Adducts of the type [CuL(B)(H₂O)_n] (B= adenine or adenosine, n = 0 or 1) have been isolated. The spectral results show that in the present copper schiff base complexes N(7) of adenosine and adenine are involved in binding. The enhancement in <em>E</em>₁_/₂ and g_ll values for the copper complexes on adduct formation with adenine and adenosine suggests the promotion of N(7) site with <em>π</em>-bonding. The higher <em>v</em>_max values observed for the adenine and adenosine adducts compared to those for cytosine and cytidine ones indicate that N(7) site of purines is preferred to N(3) of pyrimidines. The g_ll and <em>E</em>_1/2 values for the adenosine adducts are lower than those for adenine adducts, revealing that the electronic rather than the steric effects of CH₂-ribose moiety determine the extent of interaction of the purines. EPR and electrochemical studies show that the extra methyl group present in the salala adducts leads to increased stabilisation of the hydrogen bond and hence of CU^II.