Electroosmosis through α-Hemolysin That Depends on Alkali Cation Type

Area of Science:

• Biophysics
• Nanotechnology
• Physical Chemistry

Background:

• Electroosmotic flow (EOF) is crucial for transport phenomena in nanopores.
• Controlling EOF is essential for applications like molecular sensing and separation.
• Protein nanopores offer unique biological platforms for studying transport.

Purpose of the Study:

• To experimentally demonstrate and characterize electroosmotic flow in a wild-type α-hemolysin protein nanopore.
• To investigate the influence of applied voltage, salt concentration, and cation type (LiCl vs. KCl) on EOF.
• To understand how EOF affects the behavior of small neutral molecules within the nanopore.

Main Methods:

• Experimental measurements of EOF in α-hemolysin nanopores across varying voltages and salt concentrations (LiCl, KCl).
• Utilized β-cyclodextrins (βCD) as model neutral molecules to study their entry frequency and residence time.
• Developed a theoretical model incorporating pore selectivity and ion solvation to interpret experimental findings.

Main Results:

• Confirmed the existence of EOF in the α-hemolysin nanopore under diverse experimental conditions.
• Demonstrated that EOF strength is dependent on applied voltage, salt concentration, and cation identity.
• Observed significantly stronger EOF with LiCl compared to KCl, attributed to enhanced anionic selectivity of the pore.

Conclusions:

• The cation type, specifically Li+, enhances EOF in protein nanopores, offering a novel control mechanism.
• EOF strength directly impacts the entry and residence times of neutral molecules like βCD.
• This research provides a facile, non-chemical method to tune EOF in biological nanopores.