Single-Molecule-Level Quantification Based on Atomic Force Microscopy Data Reveals the Interaction between Melittin...

Area of Science:

• Biophysics
• Molecular Interactions
• Microbiology

Background:

• Melittin (Mel) is crucial for killing Gram-negative bacteria (GNB) via interactions with lipopolysaccharide (LPS).
• Understanding single-molecule forces and dissociation kinetics of Mel/LPS complexes is vital but poorly understood.

Purpose of the Study:

• To investigate single-molecule interaction forces between Mel and different forms of LPS from E. coli.
• To explore the kinetic characteristics of Mel/LPS complex dissociation.

Main Methods:

• Atomic force microscopy (AFM)-based single-molecule force spectroscopy (SMFS) was used to measure interaction forces.
• AFM-based dynamic force spectroscopy (DFS) and an advanced analytical model analyzed dissociation kinetics.

Main Results:

• Mel interacts with both rough (R)-form and smooth (S)-form LPS.
• Mel exhibits stronger specific and non-specific interactions with S-form LPS compared to R-form LPS (p < 0.05).
• Mel/S-LPS complexes show greater stability, characterized by lower dissociation rates, shorter energy barrier widths, longer bond lifetimes, and higher energy barriers.

Conclusions:

• Mel's interaction with S-form LPS is more robust and forms more stable complexes than with R-form LPS.
• O-antigen variability in S-form LPS does not significantly impact Mel interaction forces.
• Findings advance understanding of Mel/LPS micromechanics and kinetics, informing the design of novel anti-GNB drugs.