Rigidity vs Activity: Design of Gramicidin S Analogs against Multidrug-Resistant Bacteria Based on Molecular...

Area of Science:

• Biochemistry
• Medicinal Chemistry
• Molecular Biology

Background:

• Antimicrobial peptides (AMPs) show promise for combating antibiotic resistance.
• Clinical application of AMPs is hindered by toxicity and limited spectrum of activity.
• Conformational rigidity is a critical factor influencing AMP efficacy and safety.

Purpose of the Study:

• To investigate the impact of conformational rigidity on the efficacy and safety of beta-sheet antimicrobial peptide analogs.
• To design and synthesize gramicidin S-based analogs with varying degrees of structural rigidity.
• To evaluate the antimicrobial activity, cytotoxicity, and membrane interactions of these analogs.

Main Methods:

• Synthesis of stapled (GS_C-FB, GS_C-SS) and linear (GS-L) beta-sheet antimicrobial peptide analogs.
• Assessment of antimicrobial activity against Gram-positive and Gram-negative bacteria.
• Evaluation of cytotoxicity using cell-based assays.
• Structural analysis using circular dichroism spectroscopy.
• Membrane interaction studies using molecular dynamics simulations.

Main Results:

• The stapled analog GS_C-FB demonstrated potent activity against Gram-positive bacteria with reduced cytotoxicity.
• The flexible linear analog GS-L exhibited broader-spectrum activity, including against Gram-negative strains, and improved safety.
• Circular dichroism and molecular dynamics simulations revealed that flexible or moderately rigid analogs interact more effectively with membrane models.

Conclusions:

• Conformational rigidity is a key determinant in the design of effective and safe antimicrobial peptides.
• Optimizing structural flexibility can enhance antimicrobial potency and broaden the spectrum of activity.
• This study provides insights for developing next-generation antimicrobial peptide therapeutics with improved clinical profiles.