Multiscale relaxation dynamics and diffusion of myelin basic protein in solution studied by quasielastic neutron scattering

The Journal of Chemical Physics, vol. 156, pp. 025102

Abstract

We report an analysis of high-resolution quasielastic neutron scattering spectra from Myelin Basic Protein (MBP) in solution, comparing the spectra at three different temperatures (283, 303, and 323 K) for a pure D2O buffer and a mixture of D2O buffer with 30% of deuterated trifluoroethanol (TFE). Accompanying experiments with dynamic light scattering and Circular Dichroism (CD) spectroscopy have been performed to obtain, respectively, the global diffusion constant and the secondary structure content of the molecule for both buffers as a function of temperature. Modeling the decay of the neutron intermediate scattering function by the Mittag-Leffler relaxation function, ϕ(t) = Eα(−(t/τ)α) (0 < α < 1), we find that trifluoroethanol slows down the relaxation dynamics of the protein at 283 K and leads to a broader relaxation rate spectrum. This effect vanishes with increasing temperature, and at 323 K, its relaxation dynamics is identical in both solvents. These results are coherent with the data from dynamic light scattering, which show that the hydrodynamic radius of MBP in TFE-enriched solutions does not depend on temperature and is only slightly smaller compared to the pure D2O buffer, except for 283 K, where it is much reduced. In accordance with these observations, the CD spectra reveal that TFE induces essentially a partial transition from β-strands to α-helices, but only a weak increase in the total secondary structure content, leaving about 50% of the protein unfolded. The results show that MBP is for all temperatures and in both buffers an intrinsically disordered protein and that TFE essentially induces a reduction in its hydrodynamic radius and its relaxation dynamics at low temperatures.

Authors 6

1. Abir N. Hassani

   Université d'Orléans · Centre National de la Recherche Scientifique · Forschungszentrum Jülich · Centre de Biophysique Moléculaire

   Affiliation as printed

   Centre de Biophysique Moléculaire, CNRS and Université d’Orléans 1 , Rue Charles Sadron, 45071 Orléans, France

   Jülich Centre for Neutron Science (JCNS-1) and Institute of Biological Information Processing (IBI-8) 3 , Forschungszentrum Jülich GmbH, 52425 Jülich, Germany

   Synchrotron Soleil 2 , L’Orme de Merisiers, 91192 Gif-sur-Yvette, France

2. Luman Haris Aachen Institute of Physical Chemistry

   Forschungszentrum Jülich · Institut Laue-Langevin · RWTH Aachen University

   Affiliation as printed

   Institute of Physical Chemistry, RWTH Aachen University 4 , Landoltweg 2, 52056 Aachen, Germany

   Jülich Centre for Neutron Science (JCNS-1) and Institute of Biological Information Processing (IBI-8) 3 , Forschungszentrum Jülich GmbH, 52425 Jülich, Germany

   5Institut Laue Langevin, 71 Avenue des Martyrs, 38042 Grenoble Cedex 9, France

3. Markus Appel Aachen 4Institute of Physical Chemistry

   Institut Laue-Langevin · RWTH Aachen University

   Affiliation as printed

   Institut Laue Langevin 5 , 71 Avenue des Martyrs, 38042 Grenoble Cedex 9, France

   4Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany

4. Tilo Seydel Aachen 4Institute of Physical Chemistry

   Institut Laue-Langevin · RWTH Aachen University

   Affiliation as printed

   Institut Laue Langevin 5 , 71 Avenue des Martyrs, 38042 Grenoble Cedex 9, France

   4Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany

5. Andreas Maximilian Stadler Aachen Institute of Physical Chemistry

   Forschungszentrum Jülich · Institut Laue-Langevin · RWTH Aachen University

   Affiliation as printed

   Institute of Physical Chemistry, RWTH Aachen University 4 , Landoltweg 2, 52056 Aachen, Germany

   Jülich Centre for Neutron Science (JCNS-1) and Institute of Biological Information Processing (IBI-8) 3 , Forschungszentrum Jülich GmbH, 52425 Jülich, Germany

   5Institut Laue Langevin, 71 Avenue des Martyrs, 38042 Grenoble Cedex 9, France

6. Gerald Reinhard Kneller corresponding Aachen 4Institute of Physical Chemistry

   Université d'Orléans · Centre National de la Recherche Scientifique · Centre de Biophysique Moléculaire · RWTH Aachen University

   Affiliation as printed

   Centre de Biophysique Moléculaire, CNRS and Université d’Orléans 1 , Rue Charles Sadron, 45071 Orléans, France

   Synchrotron Soleil 2 , L’Orme de Merisiers, 91192 Gif-sur-Yvette, France

   4Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany