Spectral studies on the interaction between HSSC and apoCopC.

Area of Science:

• Biochemistry
• Supramolecular Chemistry
• Spectroscopy

Background:

• ApoCopC is a copper-binding protein crucial for copper homeostasis.
• Salicylaldehyde semicarbazone anion (HSSC) is a potential ligand for metal ions.

Purpose of the Study:

• To investigate the supramolecular interaction between HSSC and apoCopC.
• To elucidate the binding mechanism, stoichiometry, and thermodynamic properties of the apoCopC-HSSC complex.
• To explore the influence of copper ions on this interaction.

Main Methods:

• UV-Vis spectroscopy
• Fluorescence spectroscopy
• Fluorescence lifetime measurements
• Computational modeling (ArgusLab 4.0.1)

Main Results:

• HSSC forms a 1:1 host-guest inclusion supramolecular complex with apoCopC with a high formation constant (8.83±0.32×10^5 M⁻¹).
• The binding involves hydrogen bonds (e.g., between Met46 and HSSC) and van der Waals forces.
• HSSC quenches apoCopC fluorescence via static quenching, indicating a single binding site.
• Copper ions affect the binding affinity between HSSC and apoCopC, and vice versa, due to participation in copper coordination.

Conclusions:

• ApoCopC exhibits strong inclusion ability towards HSSC, forming a stable supramolecular complex.
• The interaction is driven by a combination of hydrogen bonding and van der Waals forces.
• Copper coordination plays a significant role in modulating the binding interaction between apoCopC and HSSC.