Revealing the mechanism of passive transport in lipid bilayers via phonon-mediated nanometre-scale density fluctuations

Mikhail Zhernenkov (1) , Dima Bolmatov (1) , Dmitry Soloviov (2, 3) , Kirill Zhernenkov (4) , Boris P. Toperverg (5, 6) , Alessandro Cunsolo (1) , Alexey Bosak (7) , Yong Q. Cai (1)

1 BNL - Brookhaven National Laboratory [Upton, NY]
2 FLNP - Frank Laboratory of Neutron Physics [Dubna]
3 Moscow Inst Phys & Technol, Dolgoprudnyi 141700, Russia
4 MDN - Magnétisme et Diffusion Neutronique
5 Petersburg Nucl Phys Inst, Gatchina 188300, Russia
6 ILL - Institut Laue-Langevin
7 ESRF - European Synchrotron Radiation Facility

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

Domaines: Sciences du Vivant [q-bio]

Mikhail Zhernenkov, Dima Bolmatov, Dmitry Soloviov, Kirill Zhernenkov, Boris P. Toperverg, et al.. Revealing the mechanism of passive transport in lipid bilayers via phonon-mediated nanometre-scale density fluctuations. Nature Communications, 2016, 7, 9 p. ⟨10.1038/ncomms11575⟩. ⟨hal-01572736⟩