Complexation of aluminum with DNA

The extent of complexation of aluminum(III) with DNA (Calf thymus, Sigma type I) was estimated by means of two experimental techniques: potentiometric titration with a fluoride selective indicator electrode and dialysis followed by aluminum determination by graphite furnace AAS. Both types of experiments indicate that aluminum(III) is bound to DNA. The data are treated by assuming an ion exchange reaction with the phosphate diester groups. Using Rt to denote the concentration of these groups the values of log [AlMn-3R]/(Rt-3[AlMn-3R])[Al3+] decrease from approx. 7.6 to 5.6 when the concentration of sodium chloride is increased from 1 to 100 mM. In the pH range 4.5-5.5 the ion exchange constant increases approximately 0.5 log units. Dialysis gives lower values for the complex formation constant than potentiometry.