Dynamical properties of the hydration shell of fully deuterated myoglobin

Klaus Achterhold, Andreas Ostermann, Martine Moulin, Michael Haertlein, Tobias Unruh, Fritz G. Parak

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

Freeze-dried perdeuterated sperm whale myoglobin was kept in a water-saturated atmosphere in order to obtain a hydration degree of 335 1H 2O molecules per one myoglobin molecule. Incoherent neutron scattering was performed at the neutron spectrometer TOFTOF at the FRM II in an angular range of q from 0.6 to 1.8Å-1 and a temperature range from 4 to 297 K. We used neutrons with a wavelength of λ αE 6 Å and an energy resolution of about 65 μeV corresponding to motions faster than 10 ps. At temperatures above 225 K, broad lines appear in the spectra caused by quasielastic scattering. For an explanation of these lines, we assumed that there are only two types of protons, those that are part of the hydration water (72%) and those that belong to the protein (28%). The protons of the hydration water were analyzed with the diffusion model of Singwi and Sjölander. In this model, a water molecule stays for a time τ0 in a bound state performing oscillatory motions. Thereafter, the molecule performs free diffusion for the time τ1 in a nonbound state followed again by the oscillatory motions for τ0 and so forth. We used the general formulation with no simplifications as τ0τ1 or τ1τ0. At room temperature, we obtained τ0 αE 104 ps and τ1 αE 37 ps. For the protein bound hydrogen, the dynamics is described by a Brownian oscillator where the protons perform overdamped motions in limited space.

Original languageEnglish
Article number041930
JournalPhysical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics
Volume84
Issue number4
DOIs
StatePublished - 25 Oct 2011

Fingerprint

Dive into the research topics of 'Dynamical properties of the hydration shell of fully deuterated myoglobin'. Together they form a unique fingerprint.

Cite this