Study on the conjugation mechanism of colistin sulfate with bovine serum albumin and effect of the metal ions on the reaction

► Complex formation is dominant for the reduction of BSA fluorescence. ► Primary binding site for drug is located in the sub-domain IIA of BSA. ► Electrostatic force played a main role between the drug and the BSA. ► The BSA structure changes upon drug complexation. ► Higher concentrations of metal ions have good effects to improve efficacy of drug except Cu2+.