Protein Transport upon Advection at the Air/Water Interface: When Charge Matters

Area of Science:

• Physical Chemistry
• Surface Science
• Biophysics

Background:

• Protein adsorption at air-water interfaces involves diffusion and advection.
• Protein interactions and interfacial layer structure depend on net charge, influenced by pH.
• The role of advection in protein adsorption kinetics and structure is not fully understood.

Purpose of the Study:

• To investigate how advection flow affects protein adsorption kinetics and interfacial layer structure.
• To determine if protein net charge (positive or negative) influences the impact of advection.
• To compare adsorption behavior of positively and negatively charged model proteins under advection and non-advection conditions.

Main Methods:

• Utilized ovalbumin and lysozyme as model proteins with varying net charges.
• Applied advection flow (water toward the interface) and controlled its absence.
• Studied interfacial layer formation and organization using neutron reflectivity and null-ellipsometry.

Main Results:

• Positively charged lysozyme and ovalbumin, with advection, formed interfacial multilayers.
• Negatively charged ovalbumin formed stable monolayers, irrespective of advection.
• Standard advection/diffusion models failed to accurately predict multilayer adsorption kinetics.

Conclusions:

• Advection flow is crucial for the formation of protein multilayers, particularly with positively charged proteins.
• Protein net charge significantly dictates whether monolayers or multilayers form under advection.
• The precise mechanism driving advection-induced multilayer formation requires further investigation.