AFM Study of pH‐Dependent Adhesion of Single Protein to TiO2 Surface. Issue 14 (4th June 2019) - Dong, Yihui
Abstract: The effect of pH‐induced electrostatic conditions on the molecular interaction force of a single lysozyme molecule with TiO2 is investigated using atomic force microscopy (AFM). The force between the charged or neutral lysozyme molecule and the TiO2 surface is measured at different pH from 3.6 to 10.8. It is found to be directly proportional to the contact area, given by an effective diameter of the lysozyme molecule, and is further qualitatively verified by the AFM‐measured friction coefficients. The results of the Derjaguin–Landau–Verwey–Overbeek theory show that the pH can change the surface charge densities of both lysozyme and TiO2, but the molecular interaction force at different pH is only dependent on the pH‐induced effective diameter of lysozyme. The molecular interaction forces, quantified at the nanoscale, can be directly used to design high‐performance liquid chromatography measurements at macroscale by tuning the retention time of a protein under varied pH conditions. They can also be applied to develop a model for predicting and controlling the chromatographic separations of proteins. Abstract : The pH‐dependent molecular interaction force between lysozyme and TiO2 is directly proportional to the contact area given by the pH‐induced effective diameter of the lysozyme molecule and this effective diameter of lysozyme is the main factor to change the molecular interaction force of protein with TiO2 surface by altering the van der Waals force.