Measuring peptide translocation into large unilamellar vesicles

Area of Science:

• Biochemistry
• Molecular Biology
• Biophysics

Background:

• Cell-penetrating peptides (CPPs) can cross cell membranes without receptors, showing potential for drug delivery.
• Antimicrobial peptides (AMPs) increasingly studied for non-lytic mechanisms, including crossing bacterial membranes to target intracellular processes.
• A strong link exists between CPPs and AMPs, necessitating robust assays to understand membrane translocation.

Purpose of the Study:

• To adapt and present a reliable assay for quantifying peptide translocation across lipid membranes.
• To provide a straightforward data analysis method for translocation ability.
• To highlight the advantages of this assay, including rate information and no need for exogenous fluorescent labels.

Main Methods:

• Utilized a Förster Resonance Energy Transfer (FRET) assay based on Matsuzaki's method.
• Measured translocation into large unilamellar lipid vesicles (LUVs) using native tryptophan fluorescence and a FRET acceptor.
• Quantified translocation by monitoring FRET signal changes due to trypsin-mediated cleavage of translocated peptides within LUVs.

Main Results:

• Demonstrated a significant drop in FRET signal for translocating peptides, indicating membrane crossing.
• Showed that the FRET signal change is greater for translocating peptides compared to non-translocating ones or controls.
• Validated the assay's ability to quantify peptide translocation over time.

Conclusions:

• The FRET-based assay effectively quantifies peptide translocation across lipid vesicles.
• This method offers advantages over other assays, including kinetic information and avoidance of fluorescent labeling.
• The assay provides a valuable tool for studying CPPs and AMPs, aiding in the development of novel drug delivery systems.