Protein diffusion in a bicontinuous microemulsion: inducing sub-diffusion by tuning the water domain size

Area of Science:

• Soft Matter Physics
• Materials Science
• Biophysics

Background:

• Microemulsions offer tunable confinement for studying molecular diffusion.
• Understanding protein behavior in confined environments is crucial for various applications.

Purpose of the Study:

• To investigate the diffusion dynamics of enhanced green fluorescent protein (GFP+) in bicontinuous sugar-surfactant microemulsions.
• To explore how varying water domain sizes influence protein diffusion and confinement effects.

Main Methods:

• Utilized bicontinuous sugar-surfactant microemulsions with controlled oil-to-water ratios to vary water domain sizes.
• Employed fluorescence correlation spectroscopy (FCS) to monitor and analyze GFP+ diffusion dynamics.
• Investigated Fickian and sub-diffusive behaviors across different confinement scales.

Main Results:

• At high water content, GFP+ exhibited standard Fickian diffusion.
• Decreasing water domain size progressively slowed GFP+ diffusion, leading to sub-diffusive behavior.
• Extreme confinement nearly immobilized GFP+, causing it to follow microemulsion matrix dynamics ('breathing mode').

Conclusions:

• Water domain size in microemulsions is a critical factor controlling protein diffusion.
• Microemulsions provide a versatile platform for studying confinement-induced changes in molecular transport.
• The study demonstrates a transition from free diffusion to confinement-dominated dynamics for GFP+.