Interactions of PAMAM Dendrimers with Bovine Serum Albumin in the Presence of Copper and Iron Ions

The effect of copper and iron ions on the interactions of G5.0 PAMAM dendrimers with bovine serum albumin (BSA) was investigated under physiological conditions by spectroscopic method. The fluorescence quenching mechanism of BSA by dendrimers is via a static quenching procedure and the presence of metal ions does not alter this quenching mode. The quenching constant KSV, the binding constant Kb, and the number of binding sites n were determined based on the fluorescence quenching of BSA by PAMAM dendrimers in the absence and presence of copper or iron ions. It has been shown that copper ion has slight impact on the PAMAM-BSA interactions, whereas the iron ion decreases the quenching efficacy and binding affinity of PAMAM dendrimers with BSA. CD data indicate that iron ions induces a decrease in the a-helix structure content of BSA, which accounts for the decreased quenching efficacy and binding affinity of PAMAM dendrimers with BSA.