Amphipols: polymers that keep membrane proteins soluble in aqueous solutions

Area of Science:

• Biochemistry
• Polymer Chemistry
• Structural Biology

Background:

• Membrane proteins are crucial for cellular functions but challenging to study due to their hydrophobic nature.
• Detergents are commonly used to solubilize membrane proteins, but can alter their native structure and function.
• A need exists for methods to handle membrane proteins in aqueous solutions without detergents.

Purpose of the Study:

• To introduce and characterize amphipols as a novel class of amphiphilic polymers.
• To demonstrate the ability of amphipols to stabilize integral membrane proteins in detergent-free aqueous solutions.
• To assess the compatibility of amphipols with various well-characterized membrane proteins.

Main Methods:

• Synthesis of amphipols with hydrophilic backbones and grafted hydrophobic chains.
• Incubation of amphipols with integral membrane proteins in aqueous buffers.
• Characterization of protein stability and native state preservation using biophysical techniques.

Main Results:

• Amphipols were successfully synthesized, exhibiting amphiphilic properties.
• Four integral membrane proteins (bacteriorhodopsin, photosynthetic reaction center, cytochrome b6f, and matrix porin) were stabilized in aqueous solution by amphipols.
• The membrane proteins remained in their native state when handled with amphipols.

Conclusions:

• Amphipols represent a promising new tool for detergent-free membrane protein research.
• These polymers facilitate the study of membrane proteins in a near-native aqueous environment.
• Amphipols offer a versatile alternative to detergents for solubilizing and stabilizing membrane proteins.