Spécificité de l'interaction DNA‐platine dosage du platine, pH métrie

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Abstract
Interaction between the sodium salt of a DNA extracted from salmon sperm (41% GC) with [Pt(NH3)4]Cl2, [Pt(NH2(CH2)2NH(CH2)2NH2Cl]Cl,cis‐Pt(NH2(CH2)2NH2)Cl2,cis‐Pt(NH3)2Cl2,trans‐Pt(NH3)2Cl2, K[Pt(C2H4)Cl3], and K2[PtCl4) indicates at least three types of complexation. A correlation is found between the change of pH and the number of platinum atoms fixed per (AT + GC) unit. The first binding site is located on the G‐C pairs (guanine–cytosine), most likely the N‐7(G) site, as it was shown in a previous study of the guanosine‐platinum salts. The fixation of the second platinum atom by the pair (AT + GC) takes place with liberation of protons. In the case of the complexescis‐Pt(NH2(CH2)2NH2)Cl2,cis‐Pt(NH3)2Cl2, andtrans‐Pt(NH3)2Cl2the second interaction seems to involve simultaneously the N‐7(A) and the N‐1(G) and N‐3(C) sites. This latter intercrosslink between guanine and cytosine obviously liberates protons and the decrease of pH is related in this case to thetranseffect of the platinum compounds. The first two platinum atoms in the reaction of K2PtCl4] or the Zeise salt, K[Pt(C2H4)Cl3] with DNA are fixed on the G‐C pairs. A maximum of six platinum atoms per (AT + GC) unit were fixed in this case. Preliminary experiments with a DNA extracted from bacteriaMicrococcus lysodeikticus(72% GC) give similar results.