Interaction of sulfanilamide and sulfamethoxazole with bovine serum albumin and adenine: Spectroscopic and molecular docking investigations

• Interactions between SAM and SMO with BSA and adenine was investigated.
• Both adenine and BSA fluorescence intensities decreased as the drug concentrations increased.
• Hydrophobic forces, electrostatic interactions and hydrogen bonds played vital roles in the binding interactions.
• Docking method provided the interactions of specific chemical groups in the complex stabilization.

Interaction between sulfanilamide (SAM) and sulfamethoxazole (SMO) with BSA and DNA base (adenine) was investigated by UV–visible, fluorescence, cyclic voltammetry and molecular docking studies. Stern–Volmer fluorescence quenching constant (Ka) suggests SMO is more quenched with BSA/adenine than that of SAM. The distance r between donor (BSA/adenine) and acceptor (SAM and SMO) was obtained according to fluorescence resonance energy transfer (FRET). The results showed that hydrophobic forces, electrostatic interactions, and hydrogen bonds played vital roles in the SAM and SMO with BSA/adenine binding interaction. During the interaction, sulfa drugs could insert into the hydrophobic pocket, where the non-radioactive energy transfer from BSA/adenine to sulfa drugs occurred with high possibility. Cyclic voltammetry results suggested that when the drug concentration is increased, the anodic electrode potential deceased. The docking method indicates aniline group is interacted with the BSA molecules.

The best binding mode between BSA with (a) SAM. The important residues of BSA are represented using lines and the ligand structure is represented using a “Ball and Stick” format. The hydrogen bonding plots between (b) SAM with BSA. The BSA residues are represented using black dots and the hydrogen bonding interactions are represented using red dots.Figure optionsDownload as PowerPoint slide