Biophysical characterization of the interaction of human albumin with an anionic porphyrin

• A novel protocol involving extensive dialysis and centrifugation eliminated aggregated protoporphyrins from the solution.
• Reliable FRET between Trp214 and the porphyrin ligands was established.
• FRET and docking simulations converge to a model consistent with experimental X-ray data.
• Photosensitization mediated by the porphyrin ligands prompts localized conformational changes in HSA.

The manuscript describes the characterization of the interaction between meso-tetrakis(p  -sulfonatophenyl)porphyrin (TSPP) and human serum albumin (HSA). TSPP is a candidate for the photosensitization of structural and functional changes in proteins while HSA provides both an excellent protein model and binding and functional characteristics that could be explored in future applications of the approach. A combination of optical spectroscopic techniques (e.g., fluorescence spectroscopy, fluorescence lifetime, circular dichroism, etc.) and computational docking simulations were applied to better characterize the TSPP/HSA interaction. Recent advances have revealed that the complex formed by TSPP and HSA has become potentially relevant to biomedical applications, biomaterials research and protein photosensitized engineering. The study has determined a likely location of the binding site that places TSPP at a site that overlaps partially with the low affinity site of ibuprofen and places one of the SO3− groups of the ligand in proximity of the Trp214 residue in HSA. The characterization will enable future studies aimed at photosensitizing non-native functions of HSA for biomedical and biomaterial applications.

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