Our research team focuses on membrane-peptide interactions, particularly elucidating the structural and functional mechanisms of membranotropic peptides, including cell-penetrating peptides (CPPs) and natural or synthetic antimicrobial peptides (AMPs), as well as membrane-associated proteins like TSPO (Translocator Protein). By combining advanced spectroscopic techniques, molecular dynamics (MD) simulations, and innovative membrane models, we aim to understand how these peptides and proteins interact with biological membranes at the atomic and molecular levels. This knowledge is critical for developing targeted therapeutic strategies and novel drug delivery systems.

1. Structural characterization using spectroscopy

We employ a multidisciplinary spectroscopic approach to probe the conformation, dynamics, and membrane interactions of peptides and proteins:

• Nuclear Magnetic Resonance (NMR) spectroscopy: Solution-state NMR (1H, 13C, 15N) is used to determine the secondary and tertiary structures of peptides in membrane-mimetic environments (e.g., micelles, bicelles). This allows us to identify structural motifs such as α-helices or β-sheets that facilitate membrane interaction. Solid-state NMR enables the study of peptides in complex membrane environments, including lipid vesicles and living cells. For example, we incorporate deuterated fatty acids into bacterial membranes to track structural changes induced by antimicrobial peptides, both lytic and non-lytic, such as spheniscin. 31P solid-state NMR and the PROCSA method (developed in-house) allow us to differentiate lipid-specific interactions, providing insights into how peptides selectively target certain membrane compositions.

• Complementary spectroscopic techniques: Circular Dichroism (CD) monitors conformational changes in peptides upon membrane binding. Fourier-Transform Infrared Spectroscopy (FTIR) and fluorescence spectroscopy provide additional details on peptide partitioning, insertion depth, and membrane perturbation.

2. Molecular Dynamics (MD) simulations

To complement experimental data, we perform MD simulations at various resolutions:

• Coarse-grained MD allows us to study large-scale membrane systems and peptide translocation over extended timescales.
• All-atom MD provides atomic-level details of peptide-lipid interactions, such as hydrogen bonding, electrostatic interactions, and conformational transitions.
• Enhanced sampling techniques, including replica-exchange MD, help explore rare or transient states, such as peptide insertion or pore formation. These simulations are essential for validating experimental observations and predicting new mechanisms of peptide-membrane interaction.

3. Innovative membrane models

We develop and utilize advanced membrane models to mimic biological environments and study peptide translocation under controlled conditions:

• Droplet Interface Bilayers (DIBs): This system allows the formation of stable lipid bilayers between aqueous droplets, enabling electrical and optical measurements of peptide-induced membrane alterations. Microfluidic integration (in collaboration with LISE and LRS) facilitates high-throughput studies.
• Asymmetric Supported Lipid Bilayers (aSLBs): Enriched with phosphatidylinositol phosphates (PIPs), these models help investigate the role of PIPs in regulating peptide-membrane interactions, particularly in cellular signaling pathways.

4. Key collaborations and applications

Our work is strengthened by collaborations with leading research groups:

• Céline Landon’s team (Orléans): We combine solid-state NMR and fluorescence microscopy to study antimicrobial and antifungal peptides in living bacteria.
• Isabelle Marcotte’s team (Montréal): We explore the use of fluorinated fatty acids and study intact red blood cells to expand the applicability of our NMR-based approaches.
• Alexandre Chenal (Institut Pasteur): Our focus is on the CyaA toxin (pertussis), where we investigate its structural reorganization during membrane translocation, with potential applications in immunotherapy.
• Fen-Ching Tsai (Institut Curie): We study PIP-regulated mechanisms using asymmetric lipid bilayers, providing insights into membrane-targeted drug delivery.

5. Long-term goals

Our research aims to:

• Decipher the structural determinants that govern the selectivity and efficiency of CPPs and AMPs.
• Develop novel peptide-based therapeutics with reduced toxicity and enhanced targeting such as chimeric amyloid-cationic peptides.
• Repurpose membrane-active proteins (e.g., TSPO) for diagnostic and therapeutic applications, such as PET imaging and anti-inflammatory strategies. By integrating structural biology, biophysics, and computational modeling, our team contributes to advancing the field of membrane biochemistry and drug discovery.