Table of Contents
Journal of Biophysics
Volume 2014 (2014), Article ID 985082, 5 pages
http://dx.doi.org/10.1155/2014/985082
Research Article

The Diamagnetic Susceptibility of the Tubulin Dimer

1Netherlands Organisation for Scientific Research, Dutch-Belgian Beamlines, European Synchrotron Radiation Facility, BP 220, 38043 Grenoble, France
2Science and Technology Facility Council (STFC), Daresbury Laboratory, Cheshire WA4 4AD, UK
3National Centre for Scientific Research (CNRS), National High Magnetic Field Laboratory, 143 Avenue de Rangueil, 31400 Toulouse, France
4CIB Centro de Investigaciones Biológicas, Ramiro de Maeztu 9, 28040 Madrid, Spain

Received 16 August 2013; Accepted 3 January 2014; Published 18 February 2014

Academic Editor: Jianwei Shuai

Copyright © 2014 Wim Bras et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

An approximate value of the diamagnetic anisotropy of the tubulin dimer, , has been determined assuming axial symmetry and that only the α-helices and β-sheets contribute to the anisotropy. Two approaches have been utilized: (a) using the value for the for an α-helical peptide bond given by Pauling (1979) and (b) using the previously determined anisotropy of fibrinogen as a calibration standard. The  JT−2 obtained from these measurements are similar to within 20%. Although Cotton-Mouton measurements alone cannot be used to estimate directly, the value we measured,  T−2cm2mg−1, is consistent with the above estimate for . The method utilized for the determination of the tubulin dimer diamagnetic susceptibility is applicable to other proteins and macromolecular assemblies as well.