LL-37 adsorption markedly increases on curved lipid membranes via distinct binding mode redistribution
Background
The interaction of antimicrobial peptides (AMPs) with lipid membranes is crucial for their function, yet their limited selectivity can lead to unintended damage to healthy eukaryotic cells. Membrane physicochemical properties, including membrane curvature, ionic strength, and lipid packing, strongly influence this interaction. Understanding how these factors modulate peptide adsorption at a molecular level is vital for designing AMPs with enhanced specificity and efficacy, moving beyond the single-molecule limit to account for collective peptide behaviors on complex membrane geometries.
Study Design
Researchers employed a molecular-theory framework within a semi-open ensemble to quantify the adsorption of LL-37, a human antimicrobial peptide, onto curved lipid membranes. The study systematically investigated how membrane curvature, ionic strength, membrane surface charge, and lipid packing jointly modulate peptide adsorption. The framework allowed for the analysis of peptide populations between distinct adsorption modes (peptides lying parallel vs. standing upright on the membrane surface), providing insights into the collective effects driving curvature sensing.
Results
The study found that while local peptide-membrane free-energy profiles were only weakly curvature-dependent, the overall amount of adsorbed LL-37 peptide increases markedly on curved geometries. This marked increase arises from collective effects, specifically the redistribution of peptide populations between distinct adsorption modes. Environmental variables significantly modulated the magnitude of peptide adsorption: > Reduced ionic strength amplifies curvature sensitivity, leading to a more pronounced increase in adsorption on curved surfaces. Membrane neutralization lowers adsorption while still preserving the fundamental binding mechanisms. Loosening lipid packing enhances adsorption, suggesting that membrane fluidity plays a critical role in peptide binding efficiency. These findings establish a molecular-level thermodynamic framework for understanding curvature-dependent peptide adsorption beyond the single-molecule limit.
Key Findings
- Overall LL-37 adsorption increases markedly on curved membrane geometries.
- Curvature sensing arises from collective effects, not just local peptide-membrane interactions.
- Peptide redistribution between parallel and upright adsorption modes drives curvature sensitivity.
- Reduced ionic strength amplifies LL-37's curvature sensitivity.
- Loosening lipid packing enhances LL-37 adsorption on membranes.
Why It Matters
This research provides a fundamental understanding of how LL-37 and similar amphipathic peptides interact with curved biological membranes, which are ubiquitous in cellular environments (e.g., vesicles, mitochondrial cristae, bacterial cell walls). For peptide users and biohackers, this implies that the efficacy of AMPs might be significantly influenced by the specific membrane curvature of their target, suggesting potential strategies for optimizing AMP design for specific membrane targets or improving drug delivery systems that rely on membrane interactions. Understanding these collective effects could lead to more selective AMPs, reducing off-target effects on healthy cells and advancing the development of novel antimicrobial therapies or even targeted drug carriers.
ll-37
antimicrobial-peptide
membrane-curvature
lipid-membranes
molecular-modeling
biophysics