ELUCIDATING AND COMPARING THE MECHANISM OF INTERACTION BETWEEN AROMATIC AMINO ACID RESIDUCES AND TiO₂ SURFACE BY SINGLE MOLECULE FORCE SPECTROSCOPY

Single molecule force spectroscopy (SMFS) is a nanoscale biophysical technique used to probe the unbinding of individual molecules from a desired surface. By varying the loading rate, dynamic SMFS experiments can be performed to evaluate the thermodynamic and kinetic parameters. These parameters are fundamental to the understanding of the interactions between a molecule and a certain surface or a pair of molecules and allow the comparison of kinetics between different systems.

The interactions of peptides or amino acids residues with metal oxide solid surfaces is important for the functionalization of these surfaces. However, the mechanism of interactions is not fully understood. Among the several important metal oxides, titanium dioxide (TiO₂) has drawn considerable attention from the researchers in the field of materials chemistry. This is because it is the most suitable and promising semiconductor catalyst in heterogeneous photocatalysis, it has high physical and chemical stability. Among the different amino acids 3,4-dihydroxyphenylalanine (DOPA) having adhesive catechol moiety is an well known anchoring building block and key constituent of MAPs. The oxidized form of DOPA plays an important role as a cross linker agent that lead to solidification of the secreted liquid protein adhesive. Several reports have shows the adhesive nature of the catechol moiety towards TiO₂ surface.

Here in, we studied using SMFS the interactions of several related aromatic amino acid residues including DOPA and its derivatives with TiO₂ coated surface. This approach allowed us to compare quantitatively the interactions of individual amino acid molecule being directly measured, from which the binding mechanisms can be inferred. The parameters evaluated from the detail analysis of the force measurements process are fundamental to understanding the kinetics and thermodynamics of the interactions.