NAP-XPS analysis at water partial pressure of Matrix Metalloproteinase 9 onto hydrophilic/hydrophobic silanized surfaces

Protein adsorption onto surfaces often induces conformational changes that affect their biological function, including enzymatic activation or deactivation. These changes are strongly influenced by the surface’s chemical nature—particularly its free energy components. Traditional methods to study these biointerfaces combine in-situ techniques (e.g., SPR, QCM-D) with surface spectroscopies (e.g., XPS, ToF-SIMS), but they operate under different environmental conditions, limiting their complementarity.

Near-Ambient Pressure XPS (NAP-XPS) overcomes this limitation by enabling spectroscopic analysis under conditions closer to physiological environments, allowing partial retention of structural water—critical for protein functionality. In previous work (BL24-CIRCE-2020094555), we optimized protocols for sample handling and beam parameters, and identified conformational differences between UHV and NAP conditions.

This proposal extends those studies to Matrix Metalloproteinase 9 (MMP9), a metalloprotein whose activity is regulated by a structural Zn center. We will analyze its adsorption onto hydrophilic and hydrophobic silanized surfaces, tracking conformational changes via the C 1s core level and Zn 2p signal. Measurements will be performed at multiple photon energies (600–2000 eV) and under controlled water partial pressures (0, 1, and 10 mbar), enabling depth-resolved analysis.

The results will contribute to a surface model for MMP9 activation/deactivation, with implications for understanding its role in diseases such as cancer, arthritis, and retinitis.