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Phys. Rev. Lett. 103, 128104 (2009) [4 pages]

Protein-Protein Interaction in Purple Membrane

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Maikel C. Rheinstädter1,2,4,*, Karin Schmalzl3, Kathleen Wood4,5,†, and Dieter Strauch6
1Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, L8S 4M1, Canada
2Canadian Neutron Beam Centre, Chalk River, Ontario, K0J 1J0, Canada
3Institut für Festkörperforschung, Forschungszentrum Jülich GmbH, JCNS at ILL, F-38042 Grenoble, France
4Institut Laue-Langevin, F-38042 Grenoble Cedex 9, France
5Institut de Biologie Structurale Jean Pierre Ebel CEA-CNRS-UJF, F-38027 Grenoble, France
6Theoretische Physik, Universität Regensburg, D-93040 Regensburg, Germany

Received 7 April 2009; published 18 September 2009

We present experimental evidence for a long-range protein-protein interaction in purple membrane (PM). The interprotein dynamics were quantified by measuring the spectrum of the acoustic phonons in the 2D bacteriorhodopsin (BR) protein lattice using inelastic neutron scattering. Phonon energies of about 1 meV were determined. The data are compared to an analytical model, and the effective spring constant for the interaction between neighboring protein trimers are determined to be k=53  N/m. Additional, optical-like excitations at 0.45 meV were found and assigned to intraprotein dynamics between neighboring BR monomers.

© 2009 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.103.128104
DOI:
10.1103/PhysRevLett.103.128104
PACS:
87.15.km, 83.85.Hf, 87.16.dj

*rheinstadter@mcmaster.ca

†Present address: Australian Nuclear Science & Technology Organisation, Bragg Institute, Menai, Australia.

 
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