MODELS FOR ENZYME-COPPER-NUCLEIC ACID INTERACTION - INTERACTION OF SOME BIOMIMETIC COPPER-COMPLEXES DERIVED FROM SALICYLALDEHYDE, GLYCINE AND ALPHA-ALANINE WITH ADENINE AND ADENOSINE

The interaction of [CuL(H2O)] (H2L=salicylideneglycine or salicylidene -alpha-alanine) with adenine and adenosine has been investigated using UV-VIS, IR and EPR spectral and electrochemical techniques. Adducts o f die type [CuL(BXH2O)n] (B = adenine or adenosine, n = 0 or 1) have b een isolated. The spectral results show that in the present copper sch iff base complexes N(7) of adenosine and adenine are involved in bindi ng. The enhancement in E1/2 and g(parallel-to) values for the copper c omplexes on adduct formation with adenine and adenosine suggests the p romotion of N(7) site with pi-bonding. The higher v(max)BAR values obs erved for the adenine and adenosine adducts compared to those for cyto sine and cytidine ones indicate that N(7) site of purines is preferred to N(3) of pyrimidines. The g(parallel-to) and E1/2 values for the ad enosine adducts are lower than those for adenine adducts, revealing th at the electronic rather than the steric effects of CH2-ribose moiety determine the extent of interaction of the purines. EPR and electroche mical studies show that the extra methyl group present in the salala a dducts leads to increased stabilisation of the hydrogen bond and hence of Cu(II).