Interaction of metallopyrazoliumylporphyrins with calf thymus DNA

The interaction of transition metal complexes of cationic porphyrins bearin g five membered rings, Meso-tetrakis(1,2-dimethylpyrazolium-4-yL)porphyrin (MPzP, M=Mn-III, Ni-II, CUII or Zn-II), with calf thymus DNA (ctDNA) has be en studied. Metalloporphyrins NiPzP and CuPzP are intercalated into the 5 ' GC3 ' step of ctDNA. MnPzP is bound edge-on at the 5 ' TA3 ' step of the m inor groove of ctDNA, while ZnPzP is bound face-on at the 5 ' TA3 ' step of the major groove of ctDNA. The binding constants of the metalloporphyrins to ctDNA range from 1.05X10(5) to 2.66X10(6) M-1 and are comparable to thos e of other reported cationic porphyrins. The binding process of the metallo pyrazoliumylporphyrins to ctDNA is endothermic and entropically driven. The :je results have revealed that the kind of central metal ions of metallopor phyrins influences the binding characteristics of the porphyrin to DNA. (C) 2001 Elsevier Science B.V. All rights reserved.