Lipid membrane-binding properties of daptomycin using surface plasmon resonance

Area of Science:

• Biochemistry and Biophysics
• Membrane Biophysics
• Antimicrobial Drug Discovery

Background:

• Daptomycin is a crucial antibiotic for treating Gram-positive bacterial infections.
• Understanding daptomycin's membrane interactions is key to optimizing its efficacy and combating resistance.
• Existing methods for studying drug-membrane interactions can be limited in scope or throughput.

Purpose of the Study:

• To develop and validate a novel Surface Plasmon Resonance (SPR) assay for quantifying daptomycin's binding affinity and kinetics to various model lipid membranes.
• To investigate the binding selectivity of daptomycin towards model membranes mimicking mammalian, Gram-positive, and Gram-negative bacterial cell envelopes.
• To assess the role of calcium ions in daptomycin's membrane binding interactions.

Main Methods:

• Development of a reproducible liposome immobilization technique on SPR sensor chips.
• Utilizing SPR spectroscopy to measure real-time binding kinetics of daptomycin to four distinct model lipid membranes.
• Comparative analysis of daptomycin's affinity for model membranes representing mammalian, Gram-positive, and Gram-negative bacteria.

Main Results:

• Daptomycin exhibited significantly higher binding affinity for the model Gram-positive bacterial membrane compared to model mammalian and Gram-negative bacterial membranes.
• The SPR system successfully demonstrated the binding selectivity of daptomycin, particularly in the presence of calcium ions.
• The developed SPR method showed reproducible liposome immobilization and reliable repeatability in kinetic analyses.

Conclusions:

• The established SPR assay is a valuable and reproducible tool for characterizing antimicrobial agent-lipid membrane interactions.
• This method provides insights into daptomycin's preferential binding to Gram-positive bacterial membranes, aiding in understanding its mechanism of action.
• The SPR assay has the potential to accelerate the discovery and optimization of new antimicrobial agents by predicting their membrane binding characteristics.