Stabilization of integral membrane proteins in aqueous solution using fluorinated surfactants

Area of Science:

• Biochemistry
• Membrane Protein Chemistry
• Surfactant Science

Background:

• Integral membrane proteins are crucial for cellular functions but challenging to study due to their hydrophobic nature.
• Classical detergents often disrupt protein structure and function, necessitating alternative solubilization agents.
• Fluorinated surfactants offer unique properties due to their low surface energy and limited hydrocarbon interactions.

Purpose of the Study:

• To synthesize and characterize novel surfactants with hydrocarbon or fluorocarbon chains and various polar head groups.
• To evaluate the efficacy of these surfactants in solubilizing and stabilizing membrane proteins, specifically chloroplast thylakoid membranes and the cytochrome b6f complex.
• To explore the potential of fluorinated surfactants as specialized tools for studying detergent-sensitive membrane proteins.

Main Methods:

• Synthesis of surfactants with tris(hydroxymethyl)acrylamidomethane (THAM) or glycosylated THAM head groups and hydrocarbon or fluorocarbon chains.
• Modification of some surfactants by oxidizing a thioether linkage to a sulfoxide to enhance aqueous solubility.
• Assessment of surfactant critical micellar concentration (CMC) based on alkyl chain properties.
• Testing surfactant performance in solubilizing thylakoid membranes and maintaining the integrity and activity of the cytochrome b6f complex.

Main Results:

• Surfactant critical micellar concentration (CMC) was primarily dictated by alkyl chain length and type.
• Fluorinated surfactants generally failed to solubilize thylakoid membranes, unlike hydrocarbon-based surfactants.
• Transferring cytochrome b6f complexes to fluorinated surfactants often led to protein aggregation, while hydrocarbon surfactants maintained solubility.
• Two specific fluorinated surfactants successfully maintained the cytochrome b6f complex in a soluble, intact, and enzymatically active state.

Conclusions:

• Alkyl chain characteristics significantly influence surfactant properties like CMC and membrane protein interaction.
• Fluorinated surfactants exhibit limited efficacy in solubilizing complex membrane structures but show promise for specific applications.
• Certain fluorinated surfactants can preserve the structure and function of membrane proteins, presenting a valuable alternative for studying proteins sensitive to conventional detergents.