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Updated: Jun 1, 2026

Multimodal Nonlinear Hyperspectral Chemical Imaging Using Line-Scanning Vibrational Sum-Frequency Generation Microscopy
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Multimodal Nonlinear Hyperspectral Chemical Imaging Using Line-Scanning Vibrational Sum-Frequency Generation Microscopy

Published on: December 1, 2023

Membrane orientation of MSI-78 measured by sum frequency generation vibrational spectroscopy

Pei Yang1, Ayyalusamy Ramamoorthy, Zhan Chen

  • 1Biophysics and Department of Chemistry, 930 North University Avenue, University of Michigan, Ann Arbor, Michigan 48109, USA.

Langmuir : the ACS Journal of Surfaces and Colloids
|May 21, 2011
PubMed

Insights

Antimicrobial peptides (AMPs) like pexiganan selectively target bacterial membranes. Sum frequency generation spectroscopy revealed pexiganan

Area of Science:

  • Biophysics
  • Membrane Biophysics
  • Spectroscopy

Background:

  • Antimicrobial peptides (AMPs) exhibit selective disruption of bacterial cell membranes over mammalian cells.
  • Understanding AMP-lipid interactions is crucial for elucidating their antimicrobial activity and selectivity.

Purpose of the Study:

  • To determine the membrane orientation of the antimicrobial peptide MSI-78 (pexiganan) in various model membranes.
  • To investigate the role of AMP-lipid interactions in the functional properties and selectivity of MSI-78.

Main Methods:

  • Utilized sum frequency generation (SFG) vibrational spectroscopy to analyze peptide-lipid interactions.
  • Employed solid-supported lipid bilayers mimicking bacterial (DPPG, POPG) and mammalian (DPPC, POPC) cell membranes.
  • Varied peptide concentration to observe concentration-dependent effects on membrane orientation.

Main Results:

  • MSI-78 associated with negatively charged bacterial membranes (DPPG) with a surface orientation (∼70° tilt).
  • Increased MSI-78 concentration on DPPG led to a more perpendicular orientation (∼25° tilt) and pore formation.
  • No significant interaction was observed between MSI-78 and zwitterionic mammalian membranes (DPPC) even at high concentrations.
  • Concentration-dependent membrane orientation and toroidal-type pore formation were observed in POPG bilayers.

Conclusions:

  • SFG spectroscopy provides valuable insights into the antibacterial activity and selectivity of MSI-78.
  • MSI-78's membrane orientation and interaction are concentration-dependent and specific to membrane charge.
  • The findings support the mechanism of toroidal-type pore formation induced by MSI-78 in bacterial membranes.

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