Exploring the binding of 4-thiothymidine with human serum albumin by spectroscopy, atomic force microscopy, and molecular modeling methods

• The interaction between 4-thiothymidine and human serum albumin was investigated.
• S4TdR has moderate affinities for HSA and binds mainly to subdomain IIA.
• The quenching mechanism of the S4TdR–HSA complexation is a static quenching.
• The morphology and aggregation of the interaction were shown by AFM.
• The hydrophobic plays an important role in the interaction between S4TdR and HSA.

The interaction of 4-thiothymidine (S4TdR) with human serum albumin (HSA) was studied by equilibrium dialysis under normal physiological conditions. In this work, the mechanism of the interaction between S4TdR and human serum albumin (HSA) was exploited by fluorescence, UV, CD circular, and SERS spectroscopic. Fluorescence and UV spectroscopy suggest that HSA intensities are significantly decreased when adding S4TdR to HAS, and the quenching mechanism of the fluorescence is static. Also, the ΔG, ΔH, and ΔS values across temperature indicated that hydrophobic interaction was the predominant binding force. The CD circular results show that there is little change in the secondary structure of HSA except the environment of amino acid changes when adding S4TdR to HSA. The surface-enhanced Raman scattering (SERS) shows that the interaction between S4TdR and HSA can be achieved through different binding sites which are probably located in the II A and III A hydrophobic pockets of HSA which correspond to Sudlow’s I and II binding sites. In addition, the molecular modeling displays that S4TdR–HSA complex is stabilized by hydrophobic forces, which result from amino acid residues. The atomic force microscopy results revealed that the single HSA molecular dimensions were larger after interaction of 4-thiothymidine. This work would be useful to understand the state of the transportation, distribution, and metabolism of the anticancer drugs in the human body, and it could provide a useful biochemistry parameter for the development of new anti-cancer drugs and research of pharmacology mechanisms.

The S4TdR–HSA was evaluated by molecular modeling. Their activity and interaction were displayed in modeling calculations.Figure optionsDownload as PowerPoint slide