Dynamics and interfacial properties of a protein-surfactant mixture system

Stimuli-responsive peptides or proteins that are able to self-assemble at the air-water interface have widespread applications including functional control of foaming. However, there is still a knowledge gap between interfacial structure of proteins and their foaming functions. Here we investigate a mixture system of a designed protein surfactant, DAMP4, and a small molecule surfactant, CPC, aiming to understand how protein and surfactant molecules interact with each other at interface and hence improve foam functions. Preliminary results based on foaming assay showed that addition of 0.7 μM of a cationic surfactant, CPC, to DAMP4 can improve both foamability and stability while using 0.05 mg DAMP4, only 17% of that needed for a single system of DAMP4. Importantly, the foams of these mixture systems can be switched on/off by adding/ removing Zn²⁺ from the bulk solution. X-ray reflectometry (beam time scheduled in early November) will be applied to investigate the dynamics and interfacial properties of this mixture system. The expected results will help understand the underlying mechanism of improving foam functions.