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Unfolding and Extraction of a Transmembrane Alpha-Helical Peptide: Dynamic Force Spectroscopy and Molecular Dynamics Simulations

Unfolding and Extraction of a Transmembrane Alpha-Helical Peptide: Dynamic Force Spectroscopy and Molecular Dynamics Simulations
Unfolding and Extraction of a Transmembrane Alpha-Helical Peptide: Dynamic Force Spectroscopy and Molecular Dynamics Simulations
An atomic force microscope (AFM) was used to visualize CWALP1923 peptides (+H3N-ACAGAWWLALALALALALALWWA-COO–) inserted in gel-phase DPPC and DSPC bilayers. The peptides assemble in stable linear structures and domains. A model for the organization of the peptides is given from AFM images and a 20 ns molecular dynamics (MD) simulation. Gold-coated AFM cantilevers were used to extract single peptides from the bilayer through covalent bonding to the cystein residue. Experimental and simulated force curves show two distinct force maxima. In the simulations these two maxima correspond to the extraction of the two pairs of tryptophan residues from the membrane. Unfolding of the peptide precedes extraction of the second distal set of tryptophans. To probe the energies involved, AFM force curves were obtained from 10 to 104 nm/s and MD force curves were simulated with 108–1011 nm/s pulling velocities (V). The velocity relationship with the force, F, was fitted to two fluctuation adhesive potential models. The first assumes the pulling produces a constant bias in the potential and predicts an F ln (V) relationship. The second takes into account the ramped bias that the linker feels as it is being driven out of the adhesion complex and scales as F (ln V)2/3.
atomic force microscopy, dynamic force spectroscopy, membrane protein unfolding, molecular dynamics simulations
0006-3495
3129-3140
Antoranz Contera, S
2fc15646-75ee-45a4-be2b-55d7a404446a
Lemaître, V
bdbd83ee-c562-4fd4-84c8-e8f6354fe17f
de Planque, M R R
a1d33d13-f516-44fb-8d2c-c51d18bc21ba
Watts, A
e234f61d-ba7f-4ef8-a632-9fec7c896c5b
Ryan, J F
b3c8b3c8-d495-4069-b620-eeba790a3aec
Antoranz Contera, S
2fc15646-75ee-45a4-be2b-55d7a404446a
Lemaître, V
bdbd83ee-c562-4fd4-84c8-e8f6354fe17f
de Planque, M R R
a1d33d13-f516-44fb-8d2c-c51d18bc21ba
Watts, A
e234f61d-ba7f-4ef8-a632-9fec7c896c5b
Ryan, J F
b3c8b3c8-d495-4069-b620-eeba790a3aec

Antoranz Contera, S, Lemaître, V, de Planque, M R R, Watts, A and Ryan, J F (2005) Unfolding and Extraction of a Transmembrane Alpha-Helical Peptide: Dynamic Force Spectroscopy and Molecular Dynamics Simulations. Biophysical Journal, 89 (5), 3129-3140. (doi:10.1529/biophysj.105.061721).

Record type: Article

Abstract

An atomic force microscope (AFM) was used to visualize CWALP1923 peptides (+H3N-ACAGAWWLALALALALALALWWA-COO–) inserted in gel-phase DPPC and DSPC bilayers. The peptides assemble in stable linear structures and domains. A model for the organization of the peptides is given from AFM images and a 20 ns molecular dynamics (MD) simulation. Gold-coated AFM cantilevers were used to extract single peptides from the bilayer through covalent bonding to the cystein residue. Experimental and simulated force curves show two distinct force maxima. In the simulations these two maxima correspond to the extraction of the two pairs of tryptophan residues from the membrane. Unfolding of the peptide precedes extraction of the second distal set of tryptophans. To probe the energies involved, AFM force curves were obtained from 10 to 104 nm/s and MD force curves were simulated with 108–1011 nm/s pulling velocities (V). The velocity relationship with the force, F, was fitted to two fluctuation adhesive potential models. The first assumes the pulling produces a constant bias in the potential and predicts an F ln (V) relationship. The second takes into account the ramped bias that the linker feels as it is being driven out of the adhesion complex and scales as F (ln V)2/3.

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More information

Published date: April 2005
Keywords: atomic force microscopy, dynamic force spectroscopy, membrane protein unfolding, molecular dynamics simulations
Organisations: Nanoelectronics and Nanotechnology

Identifiers

Local EPrints ID: 264683
URI: https://eprints.soton.ac.uk/id/eprint/264683
ISSN: 0006-3495
PURE UUID: 154aca4c-2f0c-4fd7-a9a6-7473f6ceb2d2
ORCID for M R R de Planque: ORCID iD orcid.org/0000-0002-8787-0513

Catalogue record

Date deposited: 16 Oct 2007
Last modified: 19 Nov 2019 01:43

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