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The Scientific World Journal
Volume 2013, Article ID 354730, 9 pages
http://dx.doi.org/10.1155/2013/354730
Research Article

Investigation on the Aggregation Behaviors and Filament Morphology of Tau Protein by a Simple 90° Angle Light-Scattering Assay

1Faculty of Pharmacy, Guangxi University of Chinese Medicine, P. O. Box 6, 179 Mingxiudong Road, Nanning, Guangxi 530001, China
2Department of Chemistry, Tongji University, Shanghai 200092, China

Received 11 July 2013; Accepted 6 August 2013

Academic Editors: S. Lee and R. Zakrzewski

Copyright © 2013 Hai-Lin Liao 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

The in vitro aggregation of tau constructs was monitored by a simple 90° angle light-scattering (LS) approach which was conducted directly on fluorescence instrument. At the optimum incident wavelength (550 nm, unpolarized), the sensitivity of LS was high enough to detect tau aggregation at micromolar range. The nucleation and elongation, different events in the aggregation process of 4RMBD construct (corresponding with the four repeated units of tau Microtubule Binding Domain) could be observed by this approach, as compared with ThS fluorescence assay. The validity of this technique was demonstrated over a range of tau concentrations with different tau filaments. Linear regression of scattering light against concentration yielded the x-intercept, the critical concentrations of tau constructs. The critical concentrations of 4RMBD and its S305N mutant are 5.26  M and 4.04  M respectively, indicating point mutation S305N, which is associated with FTDP-17, appear to enhance the heparin-induced tau aggregation in vitro. Furthermore, the slopes of concentration dependence curves, as well as the angle dependence, were discussed based on the filaments morphology examined by electron microscopy and ultrasonication experiment.