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Tulane School of Medicine

Wimley Lab

I used membrane protein models and combinatorial chemistry to design peptide assemblies that interact with lipid bilayers, for use in drug design, drug delivery, and diagnostics.

May 2022 – Oct 2023

Research Assistant

In Dr. William Wimley's lab (George A. Adrouny Professor of Biochemistry at Tulane School of Medicine),1 I used PDB membrane protein models and combinatorial chemistry to design peptide assemblies that interact with membrane proteins and lipid bilayers.

I used high-throughput screening to identify peptides that form pores across the membrane. These included the pHD peptide family (nanopores activated at pH < 6)2 and macrolittins, which were evolved from melittin,3 the main cytolytic component of bee venom.4

The lab's method, synthetic molecular evolution, runs repeated rounds of library design, synthesis, and screening to select peptides with specific membrane activity.5 It has produced antibacterial peptides that work in whole blood6 and pH-triggered pore-formers aimed at drug delivery.2

Lab Context

  • •Combinatorial peptide libraries screened by iterative synthetic molecular evolution5
  • •Collaboration with the Hristova Lab at Johns Hopkins University7
  • •Applications spanning infectious disease, oncology, and diagnostics

Peptide–membrane interaction, by environment pH

Cross-section of a lipid bilayer. Drag pH or switch peptide family to assemble or dissolve the transmembrane pore.

Pore assembled, cargo leaking
pH 5.5
6.07.4

pH 6.0: pHD nanopore threshold · pH 7.4: physiological. Below 6.0 the peptides insert and assemble a pore.

  • Lipid headgroup
  • Hydrophobic core
  • Peptide α-helix
  • Pore lumen
  • Cargo / dye

Schematic model, not to scale. The states shown follow the facts on this page: pHD peptides gate at pH < 6; macrolittins form pores at neutral pH with no pH trigger.2,3

Peptide Families

Peptide families from the lab.

The Wimley Lab has used synthetic molecular evolution to develop several peptide families, each with different membrane activity and a different intended use.

Macrolittins

Evolved from melittin (bee venom)

Form large pores in lipid membranes at very low peptide-to-lipid ratios to release macromolecule-sized cargo, with no measurable toxicity to human cells.3,8

pHD Peptides

Synthetic molecular evolution

pH-dependent nanopores that stay inactive at physiological pH (7.4) and open at acidic pH (< 6), which makes them candidates for tumor-targeted delivery.2

MelP5

Gain-of-function melittin variant

A potent equilibrium pore-former evolved from melittin. It releases macromolecule-sized cargo from lipid vesicles and served as the parent for the macrolittins.9,8

Applications

Potential applications.

Antibiotic-Resistant Drug Design

These peptides kill bacteria by punching pores in their membranes, so they sidestep the resistance mechanisms that target metabolic drugs. They stay active in whole blood, a test most antimicrobial peptides fail.6

pH-Responsive Drug Delivery

The pHD (pH-dependent) peptides form nanopores only at pH < 6. Tumor microenvironments are acidic, so a carrier built on them could stay inactive in healthy tissue and release its drug at the tumor.2,10

Biosensor Engineering

Self-assembling nanopores can be engineered to detect specific molecules. Because the pore geometry is controlled, they could support single-molecule detection of infectious disease and cancer biomarkers.11

Sources

  1. 1William C. Wimley, PhD · Tulane University School of MedicineGeorge A. Adrouny Endowed Professor, Department of Biochemistry and Molecular Biology.
  2. 2pH-Triggered, Macromolecule-Sized Poration of Lipid Bilayers by Synthetically Evolved Peptides · Wiedman G, et al., Journal of the American Chemical Society, Jan 2017pHD peptides: little activity at physiological pH, macromolecule-sized pores at acidic pH (apparent pKa 5.5–5.8); proposed for cargo release and cancer therapeutics.
  3. 3Potent Macromolecule-Sized Poration of Lipid Bilayers by the Macrolittins, A Synthetically Evolved Family of Pore-Forming Peptides · Li S, et al., Journal of the American Chemical Society, May 2018Macrolittins release macromolecules from PC vesicles at neutral pH at peptide-to-lipid ratios as low as 1:1000.
  4. 4Bee Venom and Its Two Main Components—Melittin and Phospholipase A2—As Promising Antiviral Drug Candidates · Yaacoub C, et al., Pathogens, Nov 2023
  5. 5Synthetic Molecular Evolution of Peptides · Wimley Lab, Tulane School of MedicineIterative design and screening of combinatorial peptide libraries.
  6. 6Synthetic molecular evolution of host cell-compatible, antimicrobial peptides effective against drug-resistant, biofilm-forming bacteria · Starr CG, et al., PNAS, Apr 2020Peptides stay active in concentrated human blood cells, where typical antimicrobial peptides lose activity; no measurable resistance over 10 passages.
  7. 7Pore-Forming Peptides · Wimley Lab, Tulane School of MedicineCollaboration with the Hristova Lab at Johns Hopkins.
  8. 8Structural Determinants of Peptide Nanopore Formation · Sun L, Hristova K, Bondar A-N, Wimley WC, ACS Nano, 2024Macrolittins evolved from melittin via MelP5; nanopores at very low concentration with essentially no cytolytic activity against cell membranes.
  9. 9Highly efficient macromolecule-sized poration of lipid bilayers by a synthetically evolved peptide · Wiedman G, et al., Journal of the American Chemical Society, Mar 2014MelP5, a gain-of-function melittin variant, forms equilibrium pores that pass macromolecules.
  10. 10The Acidic Tumor Microenvironment as a Driver of Cancer · Boedtkjer E, Pedersen SF, Annual Review of Physiology, Feb 2020
  11. 11De novo design of a nanopore for single-molecule detection that incorporates a β-hairpin peptide · Shimizu K, et al., Nature Nanotechnology, Jan 2022Self-assembling peptide nanopores used for single-molecule detection of DNA and polypeptides.