Melittin Aggregation in Aqueous Solutions: Insight from Molecular Dynamics Simulations

Area of Science:

• Biophysics
• Computational chemistry
• Molecular biology

Background:

• Melittin, a natural peptide, exhibits aggregation in aqueous solutions, transitioning from monomer to tetramer and undergoing coil-to-helix changes.
• The precise molecular mechanisms governing melittin self-aggregation in solution remain incompletely understood.

Purpose of the Study:

• To elucidate the molecular mechanisms of melittin self-aggregation in aqueous solutions using atomistic detail.
• To investigate the influence of environmental factors like peptide concentration, temperature, and ionic strength on melittin aggregation.
• To provide a molecular-level explanation for the observed tetramer formation and the cessation of aggregation at this stage.

Main Methods:

• Atomistic molecular dynamics simulations to observe melittin self-aggregation.
• Unbiased and metadynamics simulations to analyze aggregation pathways.
• Integration of computer simulations with electrical double layer theory to explain aggregation limits.

Main Results:

• Confirmed the stability of the melittin tetramer in solution.
• Observed and detailed the aggregation of four melittin monomers into a tetramer for the first time in atomistic detail.
• Simulated aggregation dependencies on concentration, temperature, and ionic strength align with experimental data.
• Proposed a sequential monomer addition mechanism for melittin self-aggregation.
• Provided evidence suggesting aggregation halts at the tetramer due to electrical double layer interactions.

Conclusions:

• The study explains experimental observations of melittin aggregation at the molecular level.
• A sequential monomer addition mechanism is proposed for melittin self-aggregation.
• Electrical double layer theory helps explain why melittin aggregation stops at the tetramer.
• Findings offer quantitative mechanistic insights for potential melittin engineering to enhance efficacy and safety.