Study on the interaction between 21-(Ph-NN)-NCTPP and bovine serum albumin by spectroscopic techniques

• The interaction between BSA and 21-(ph-NN)-NCTPP was studied.
• The fluorescence quenching mechanism was explored.
• The binding constants and binding sites were calculated.
• Hydrophobic interaction played a major role in the binding process.
• High probability of the energy transfer from BSA to 21-(ph-NN)-NCTPP occurred.

The interaction between 21-(Ph-NN)-NCTPP and bovine serum albumin (BSA) was investigated by fluorescence and ultraviolet–visible (UV–Vis) spectroscopy under imitated physiological conditions. The results showed that the intrinsic fluorescence of BSA was quenched strongly by 21-(Ph-NN)-NCTPP. The binding constants (Ka) and the binding sites (n) were obtained at three different temperatures (298, 304, and 310 K). The thermodynamic parameters (ΔH, ΔS and ΔG) of the interaction system were calculated, the results indicated that the binding process was spontaneous and the hydrophobic interaction played a major role in [21-(Ph-NN)-NCTPP]–BSA binding process. Based on the Förster non-radiation energy transfer theory, the binding distance from 21-(Ph-NN)-NCTPP to BSA was estimated to be about 3.51 nm. What’s more, the synchronous fluorescence spectra indicated that the conformation of BSA has not been changed.

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