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Updated: Jul 31, 2025
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Gramicidin-based Fluorescence Assay; for Determining Small Molecules Potential for Modifying Lipid Bilayer Properties
Published on: October 13, 2010
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Temperature-Induced Effects on the Structure of Gramicidin S
Ngaatendwe B C Pfukwa1, Marina Rautenbach2, Neil T Hunt3
1Department of Physics, Laser Research Institute, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa.
The Journal of Physical Chemistry. B
|May 1, 2023
Summary
Gramicidin S (GS) structure in a membrane mimetic environment was studied using 2D-IR spectroscopy. Two melting transitions were identified, revealing structural changes and aggregate disruption, aiding in the development of new GS analogues.
Area of Science:
- Biophysics
- Spectroscopy
- Structural Biology
Background:
- Gramicidin S (GS) is a cyclic peptide antibiotic with antimicrobial properties.
- Understanding GS structure in membrane-like environments is crucial for developing new analogues with enhanced bioactivity.
Purpose of the Study:
- To investigate the structural and conformational changes of Gramicidin S (GS) in a model membrane mimetic environment (1-octanol) using advanced spectroscopic techniques.
- To identify and characterize the melting transitions of GS aggregates and oligomers.
Main Methods:
- One-dimensional (1D) and two-dimensional (2D) Infrared (IR) spectroscopy were employed to analyze the amide I band of GS.
- Spectroscopic measurements were conducted at varying temperatures to observe structural transitions.
- Quantum mechanical/molecular mechanics (QM/MM) simulations and second derivative analyses were used to complement spectroscopic data.
Main Results:
- Two distinct melting transition temperatures were identified for GS.
- The first transition (41-47 °C) indicated the disassembly of GS aggregates/oligomers.
- The second transition (57 ± 2 °C) involved significant changes in GS β-sheet hydrogen bonds, suggesting a shift towards intrapeptide bonds.
Conclusions:
- 2D-IR spectroscopy effectively differentiates melting transitions in oligomerized GS structures due to its sensitivity to vibrational coupling.
- The study provides insights into GS structural dynamics and the role of side chains in these transitions.
- Findings contribute to a better understanding of GS structure for the formulation of improved bioactive analogues.
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