Fatty Acid/Phospholipid Blended Membranes: A Potential Intermediate State in Protocellular Evolution

Area of Science:

• Origin of life studies
• Biochemistry
• Membrane biophysics

Background:

• Primitive cell membranes need stability and permeability for essential reactions.
• Pure fatty acid or phospholipid membranes struggle to balance these properties.
• The transition from fatty acid to phospholipid membranes is a key evolutionary question.

Purpose of the Study:

• To investigate a hybrid membrane system composed of oleic acid (OA) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC).
• To determine if this hybrid system can simultaneously provide membrane stability and permeability to polar solutes.
• To assess the compatibility of this system with early cellular reactions.

Main Methods:

• Creation and characterization of hybrid vesicles using OA and POPC.
• Assessment of vesicle stability in the presence of divalent cations (Mg2+).
• Measurement of vesicle permeability to small charged molecules like nucleotides and Mg2+.

Main Results:

• The OA/POPC hybrid vesicles demonstrated high stability against Mg2+.
• These vesicles maintained permeability to nucleotides and Mg2+.
• The hybrid system supported nonenzymatic RNA replication and was compatible with ribosomal translation.

Conclusions:

• Blended membranes of fatty acids and phospholipids can bridge the gap between primitive and modern cell membranes.
• This transition likely occurred through intermediate amphiphile mixtures, not requiring protein transporters.
• Hybrid membranes offer a plausible mechanism for supporting early cellular functions during membrane evolution.