Vibrational lifetimes of hydrated phospholipids

¹ Fachbereich Physik, Universität Osnabrück - Barbarastraße 7, D-49076 Osnabrück, Germany
² Department of Physics, Sharif University of Technology - Tehran 11365-9161, Iran
³ Institute of Physics, Carl von Ossietzky University - D-26111 Oldenburg, Germany
⁴ Department of Bionanoscience, Kavli Institute of Nanoscience, Faculty of Applied Sciences, Delft University of Technology - Lorentzweg 1, 2628 CJ Delft, The Netherlands
⁵ Mork Family Department of Chemical Engineering and Materials Science, University of Southern California Los Angeles, CA 90089-1211, USA

^(a) A.MashaghiTabari@tudelft.nl

Received: 2 March 2013
Accepted: 8 April 2013

Abstract

Large-scale ab initio molecular-dynamics simulations have been carried out to compute, at human-body temperature, the vibrational modes and lifetimes of pure and hydrated dipalmitoylphosphatidylcholine (DPPC) lipids. The projected atomic vibrations calculated from the spectral energy density are used to compute the vibrational modes and the lifetimes. All the normal modes of the pure and hydrated DPPC and their frequencies are identified. The computed lifetimes incorporate the full anharmonicity of the atomic interactions. The vibrational modes of the water molecules close to the head group of DPPC are active (possess large projected spectrum amplitudes) in the frequency range 0.5–55 THz, with a peak at 2.80 THz in the energy spectrum. The computed lifetimes for the high-frequency modes agree well with the recent data measured at room temperature where high-order phonon scattering is not negligible. The computed lifetimes of the low-frequency modes can be tested using the current experimental capabilities. Moreover, the approach may be applied to other lipids and biomolecules, in order to predict their vibrational dispersion relations, and to study the dynamics of vibrational energy transfer.