Adsorption of polyelectrolyte-like proteins to silica surfaces and the impact of pH on the response to ionic strength. A Monte Carlo simulation and ellipsometry study.
The adsorbed amount of the polyelectrolyte-like protein histatin 5 on a silica surface depends on the pH and the ionic strength of the solution. Interestingly, an increase in ionic strength affects the adsorbed amount differently depending on the pH of the solution, as shown by ellipsometry measurements (Hyltegren, 2016). We have tested the hypothesis that the same (qualitative) trends can be found also from a coarse-grained model that takes all charge-charge interactions into account within the frameworks of Gouy-Chapman and Debye-Hückel theories.



Using the same coarse-grained model as in our previous Monte Carlo study of single protein adsorption (Hyltegren, 2016), simulations of systems with many histatin 5 molecules were performed and then compared with ellipsometry measurements. The strength of the short-ranged attractive interaction between the protein and the surface was varied.



The coarse-grained model does not qualitatively reproduce the pH-dependence of the experimentally observed trends in adsorbed amount as a function of ionic strength. However, the simulations cast light on the balance between electrostatic attraction between protein and surface and electrostatic repulsion between adsorbed proteins, the deficiencies of the Langmuir isotherm, and the implications of protein charge regulation in concentrated systems.
Division of Theoretical Chemistry, Lund University, P.O.B. 124, SE-221 00 Lund, Sweden. Electronic address: kristin.hyltegren@teokem.lu.se.
Kristin
K
Hyltegren
Division of Theoretical Chemistry, Lund University, P.O.B. 124, SE-221 00 Lund, Sweden.
Marie
M
Skepö
D000327:Adsorption; D006863:Hydrogen-Ion Concentration; D009010:Monte Carlo Method; D009994:Osmolar Concentration; D000071228:Polyelectrolytes / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D055672:Static Electricity
D000071228:Polyelectrolytes; D011506:Proteins; D012822:Silicon Dioxide
00-01; 99-00; Adsorption; Charge regulation; Coarse graining; Ellipsometry; Histatin 5; Intrinsically disordered proteins; Monte Carlo simulations; Polyelectrolytes