riDOM, a cell penetrating peptide. Interaction with phospholipid bilayers

Area of Science:

• Biophysics
• Materials Science
• Biochemistry

Background:

• Melittin, a model peptide for membrane interactions, exhibits significant cytolytic and toxicological effects, limiting its use.
• Retro-inverso-melittin (ri-melittin) offers a modified structure to overcome melittin's limitations.
• Covalent linkage of ri-melittin to 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (riDOM) aims to improve its properties for membrane interactions.

Purpose of the Study:

• To investigate the interaction of the novel lipid-peptide conjugate, riDOM, with phospholipid membranes.
• To characterize the structural and thermodynamic properties of riDOM in aqueous and membrane environments.
• To assess the potential of riDOM as a safer alternative to melittin for membrane applications.

Main Methods:

• Circular dichroism (CD) spectroscopy to analyze secondary structure.
• Dynamic light scattering and ζ-potential measurements for nanoparticle characterization.
• High-sensitivity isothermal titration calorimetry (ITC) to determine binding thermodynamics.
• (31)P NMR spectroscopy to study membrane structure changes.

Main Results:

• riDOM forms stable, cationic nanoparticles (~13nm diameter) with good water solubility and high affinity for DNA and lipid membranes.
• Upon membrane insertion, riDOM nanoparticles dissociate, forming transient pores with significantly reduced membrane leakiness compared to melittin.
• riDOM insertion into membranes is entropy-driven, with half of its lipid hydrophobic surface involved in lipid-peptide interactions, ensuring dual solubility.
• The β-structure of ri-melittin remains largely unchanged upon transfer to the membrane, while the lipid bilayer structure is preserved.

Conclusions:

• riDOM represents a promising peptide-lipid conjugate with enhanced solubility and reduced toxicity compared to native melittin.
• The unique packing of riDOM within lipid membranes facilitates its dual solubility and controlled membrane interaction.
• riDOM's properties suggest potential applications in areas requiring safe and effective peptide-membrane interactions, such as drug delivery or biomaterials.