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          Institute: MPI für medizinische Forschung     Collection: Jahrbuch 2012     Display Documents

ID: 638150.0, MPI für medizinische Forschung / Jahrbuch 2012
Investigation of Model Membrane Disruption Mechanism by Melittin using Pulse Electron Paramagnetic Resonance Spectroscopy and Cryogenic Transmission Electron Microscopy
Translation of Title:Investigation of Model Membrane Disruption Mechanism by Melittin using Pulse Electron Paramagnetic Resonance Spectroscopy and Cryogenic Transmission Electron Microscopy
Authors:Gordon−Grossman, Michal; Zimmermann, Herbert; Wolf, Sharon G; Shai, Yechiel; Goldfarb, Daniella
Date of Publication (YYYY-MM-DD):2012-01-12
Title of Journal:Journal of Physical Chemistry B
Journal Abbrev.:J. Phys. Chem. B
Issue / Number:1
Start Page:179
End Page:188
Review Status:Peer-review
Audience:Experts Only
Intended Educational Use:No
Abstract / Description:Studies of membrane peptide interactions at the molecular level are important for understanding essential processes such as membrane disruption or fusion by membrane active peptides. In a previous study, we combined several electron paramagnetic resonance (EPR) techniques, particularly continuous wave (CW) EPR, electron spin echo envelope modulation (ESEEM), and double electron−electron resonance (DEER) with Monte Carlo (MC) simulations to probe the conformation, insertion depth, and orientation with respect to the membrane of the membrane active peptide melittin. Here, we combined these EPR techniques with cryogenic transmission electron microscopy (cryo−TEM) to examine the effect of the peptide/phospholipid (P/PL) molar ratio, in the range of 1:400 to 1:25, on the membrane shape, lipids packing, and peptide orientation and penetration. Large unilamellar vesicles (LUVs) of DPPC/PG (7:3 dipalmitoylphosphatidylcholine/egg phosphatidylglycerol) were used as model membranes. Spin−labeled peptides were used to probe the peptide behavior whereas spin−labeled phspholipids were used to examine the membrane properties. The cryo−TEM results showed that melittin causes vesicle rupture and fusion into new vesicles with ill−defined structures. This new state was investigated by the EPR methods. In terms of the peptide, CW EPR showed decreased mobility, and ESEEM revealed increased insertion depth as the P/PL ratio was raised. DEER measurements did not reveal specific aggregates of melittin, thus excluding the presence of stable, well−defined pore structures. In terms of membrane properties, the CW EPR reported reduced mobility in both polar head and alkyl chain regions with increasing P/PL. ESEEM measurements showed that, as the P/PL ratio increased, a small increase in water content in the PL headgroup region took place and no change was observed in the alkyl chains part close to the hydrophilic region. In terms of lipid local density, opposite behavior was observed for the polar head and alkyl chain regions with increasing P/PL; while the DPPC density increased in the polar head region, it decreased in the alkyl chain region. These results are consistent with disruption of the lipid order and segregation of the PL constituents of the membrane as a consequence of the melittin binding. This work further demonstrates the applicability and potential of pulse EPR techniques for the study of peptide−membrane interactions
External Publication Status:published
Document Type:Article
Communicated by:Wulf Kaiser
Affiliations:MPI für medizinische Forschung/Abteilung Biophysik
MPI für medizinische Forschung/Abteilung Biomolekulare Mechanismen
MPI für medizinische Forschung/Arbeitsgruppe Zimmermann
MPI für medizinische Forschung/Abteilung Molekulare Physik
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