Binding of Sudan II and Sudan IV to bovine serum albumin: Comparison studies

In this paper, we report the interaction of Sudan II and Sudan IV to bovine serum albumin (BSA). Structural analysis showed that both Sudan II and Sudan IV interact mainly with BSA at the hydrophobic pocket and via Van der Waals forces. The number of bound Sudan molecule for each protein molecule was approximately 1. The overall binding constants at 293 K (20 °C) estimated for Sudan II and Sudan IV were 1.22 × 10⁴ M⁻¹ and 1.48 × 10⁴ M⁻¹, respectively. BSA backbone structure was damaged by the dyes with more severe phenomenon observed for Sudan IV. For two Sudan dyes with the same concentration, Sudan IV could cause more alterations on CD spectra of BSA with slight decrease of α-helical content and increase of β-sheet content, suggesting a partial protein unfolding.