Effect of melittin on water diffusion and membrane structure in DMPC lipid bilayers

¹ Department of Physics and Astronomy and Research Reactor, University of Missouri - Columbia, MO 65211, USA
² Oak Ridge National Laboratory - Oak Ridge, TN 37830, USA
³ Department of Chemistry, Technical University of Denmark, IK 207 DTU - DK, 2800 Lyngby, Denmark
⁴ Center for Neutron Research, National Institute of Standards and Technology - Gaithersburg, MD 20899-6102, USA
⁵ Department of Materials Science and Engineering, University of Maryland - College Park, MD 20742, USA

^(a) taubh@missouri.edu

Received: 5 June 2018
Accepted: 18 July 2018

Abstract

Quasielastic neutron scattering (QENS) is well suited for studying the dynamics of water in proximity to supported membranes whose structure can be characterized by atomic force microscopy (AFM). Here we use QENS to investigate the effect of an adsorbed peptide (melittin) on water diffusion near a single-supported zwitterionic membrane (DMPC). Measurements of the incoherent elastic neutron intensity as a function of temperature provide evidence of bulk-like water freezing onto the melittin, which AFM images indicate coalesces into peptide-lipid domains as the peptide concentration increases. Analysis of the QENS spectra indicates that, at sufficiently high melittin concentrations, a water component diffusing more slowly than bulk-like water first freezes onto the bound melittin.