We combine Brillouin neutron scattering measurements with recent inelastic X-ray scattering [Zhernenkov et al. Nat. Commun. 2016, 7, 11575] to propose a model for the collective dynamics of phospholipid bilayers. Neutron and X-ray spectra were fitted by the model response function associated with the Hamiltonian of an interacting-phonon system. This approach allows for a comprehensive and unprecedented picture of the vibrational collective features of phospholipids. At low wavevectors Q, the dispersion relations can be interpreted in terms of two acoustic-like modes, one longitudinal and one transverse, plus a dispersionless optic-like mode. The transverse mode of the liquid phase shows a phonon gap that can be linked to a passive transport mechanism through membranes, an interpretation that was proposed in Zhernenkov et al. At higher Q values, the interaction of the longitudinal acoustic excitation with the dispersionless mode gives rise to a pattern that is consistent with avoided-crossing behavior. Evidence is found for a slow- to fast-sound transition, similar to bulk water and other biomolecules.

Multiple Interacting Collective Modes and Phonon Gap in Phospholipid Membranes

D'ANGELO, GIOVANNA;DE FRANCESCO, ALESSIO;Sacchetti, Francesco;Petrillo, Caterina;Paciaroni, Alessandro
2018

Abstract

We combine Brillouin neutron scattering measurements with recent inelastic X-ray scattering [Zhernenkov et al. Nat. Commun. 2016, 7, 11575] to propose a model for the collective dynamics of phospholipid bilayers. Neutron and X-ray spectra were fitted by the model response function associated with the Hamiltonian of an interacting-phonon system. This approach allows for a comprehensive and unprecedented picture of the vibrational collective features of phospholipids. At low wavevectors Q, the dispersion relations can be interpreted in terms of two acoustic-like modes, one longitudinal and one transverse, plus a dispersionless optic-like mode. The transverse mode of the liquid phase shows a phonon gap that can be linked to a passive transport mechanism through membranes, an interpretation that was proposed in Zhernenkov et al. At higher Q values, the interaction of the longitudinal acoustic excitation with the dispersionless mode gives rise to a pattern that is consistent with avoided-crossing behavior. Evidence is found for a slow- to fast-sound transition, similar to bulk water and other biomolecules.
2018
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11391/1437110
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