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Updated: Aug 16, 2026
Determination of Protein-ligand Interactions Using Differential Scanning Fluorimetry
Published on: September 13, 2014
Effect of hexafluoroisopropanol alcohol on the structure of melittin: a molecular dynamics simulation study
Danilo Roccatano1, Marco Fioroni, Martin Zacharias
1School of Engineering and Science, International University of Bremen, Campus Ring 1, D-28725 Bremen, Germany. d.roccatano@iu-bremen.de
Abstract:
The molecular mechanism by which HFIP stabilizes the alpha-helical structure of peptides is not well understood. In the present study, we use melittin as a model to gain insight into the details of the atomistic interactions of HFIP with the peptide. We have performed extensive comparative molecular dynamics simulations (up to 100 nsec) in the absence and in the presence of HFIP. In agreement with recent NMR experiments, the simulations show rapid loss of tertiary structure in water at pH 2 but much higher helicity in 35% HFIP. The MD simulations also indicate that melittin adopts a highly dynamic global structure in 35% HFIP solution with two alpha-helical segments sampling a wide range of angular orientations. The analysis of the HFIP distribution shows the tendency of HFIP to aggregate around the peptide, increasing the local cosolvent concentration to more than two times that in the bulk concentration. The correlation of local peptide structure with HFIP coating suggests that displacement of water at the peptide surface is the main contribution of HFIP in stabilizing the secondary structure of melittin. Finally, a stabilizing effect promoted by the presence of counter-ions was also observed in the simulations.
Insights
Hexafluoroisopropanol (HFIP) stabilizes peptide alpha-helical structures by aggregating around the peptide, displacing water. This molecular insight, using melittin, reveals HFIP
Area of Science:
- Biochemistry
- Physical Chemistry
- Computational Biology
Background:
- The mechanism of alpha-helical stabilization by hexafluoroisopropanol (HFIP) in peptides remains unclear.
- Melittin serves as a model peptide to investigate HFIP-peptide interactions at an atomic level.
Purpose of the Study:
- To elucidate the atomistic interactions between HFIP and melittin.
- To understand the role of HFIP in stabilizing peptide secondary structures.
Main Methods:
- Comparative molecular dynamics (MD) simulations up to 100 ns.
- Simulations conducted in aqueous solution and in the presence of 35% HFIP.
- Analysis of peptide structure, HFIP distribution, and counter-ion effects.
Main Results:
- Simulations confirm higher helicity of melittin in 35% HFIP compared to water at pH 2, consistent with NMR data.
- Melittin exhibits a dynamic global structure in HFIP, with two helical segments.
- HFIP aggregates around the peptide, locally increasing concentration and displacing water.
- Counter-ions also demonstrated a stabilizing effect on the peptide structure.
Conclusions:
- HFIP stabilizes melittin's alpha-helical structure primarily by displacing water molecules at the peptide surface.
- The local concentration of HFIP around the peptide is significantly higher than in the bulk solution.
- Counter-ions contribute to secondary structure stabilization.
