title: Revealing the mechanism of passive transport in lipid bilayers via phonon-mediated nanometre-scale density fluctuations.
abstract: The passive transport of molecules through a cell membrane relies on thermal motions of the lipids. However, the nature of transmembrane transport and the precise mechanism remain elusive and call for a comprehensive study of phonon excitations. Here we report a high resolution inelastic X-ray scattering study of the in-plane phonon excitations in 1,2-dipalmitoyl-sn-glycero-3-phosphocholine above and below the main transition temperature. In the gel phase, for the first time, we observe low-frequency transverse modes, which exhibit a phonon gap when the lipid transitions into the fluid phase. We argue that the phonon gap signifies the formation of short-lived nanometre-scale lipid clusters and transient pores, which facilitate the passive molecular transport across the bilayer plane. Our findings suggest that the phononic motion of the hydrocarbon tails provides an effective mechanism of passive transport, and illustrate the importance of the collective dynamics of biomembranes.
authors.affiliation: National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: Mikhail
authors.identifier: 0000-0003-3604-0672
authors.initials: M
authors.lastname: Zhernenkov
authors.affiliation: National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: Dima
authors.initials: D
authors.lastname: Bolmatov
authors.affiliation: Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna 141980, Russia.|Moscow Institute of Physics and Technology, Dolgoprudny 141700, Russia.
authors.forename: Dmitry
authors.initials: D
authors.lastname: Soloviov
authors.affiliation: Institut Nanosciences et Cryogénie, Commissariat à l'Energie Atomique, Grenoble 38054, France.
authors.forename: Kirill
authors.initials: K
authors.lastname: Zhernenkov
authors.affiliation: Petersburg Nuclear Physics Institute, Gatchina 188300, Russia.|Institut Laue Langevin, 6, rue Jules Horowitz, Grenoble 38042, France.
authors.forename: Boris P
authors.initials: BP
authors.lastname: Toperverg
authors.affiliation: National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Cunsolo
authors.affiliation: European Synchrotron Radiation Facility, Grenoble 38000, France.
authors.forename: Alexey
authors.initials: A
authors.lastname: Bosak
authors.affiliation: National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: Yong Q
authors.initials: YQ
authors.lastname: Cai
mesh_terms: D001692:Biological Transport; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry; D008051:Lipid Bilayers / Q000378:metabolism*; D053758:Nanoparticles / Q000737:chemistry*; D060739:Phonons; D014965:X-Rays
chemical_list: D008051:Lipid Bilayers; D004134:Dimyristoylphosphatidylcholine