Formation of amyloid-like aggregates through the attachment of protein molecules to a Congo red scaffolding framework ordered under the influence of an electric field

Abstract

This study describes a technique which makes it possible to introduce the amyloid-like order to protein aggregates by using the scaffolding framework built from supramolecular, fibrillar Congo red structures arranged in an electric field. The electric field was used not only to obtain a uniform orientation of the charged dye fibrils, but also to make the fibrils long, compact and rigid due to the delocalization of pi electrons, which favors ring stacking and, as a consequence, results in an increased tendency to self-assemble. The protein molecules (immunoglobulin L chain lambda, ferritin) attached to this easily adsorbing dye framework assume its ordered structure. The complex precipitating as plate-like fragments shows birefringence in polarized light. The parallel organization of fibrils can be observed with an electron microscope. The dye framework may be removed via reduction with sodium dithionite, leaving the aggregated protein molecules in the ordered state, as confirmed by X-ray diffraction studies.© Versita Warsaw and Springer-Verlag Berlin Heidelberg.

Amyloids, Congo red and the apple-green effect

“…This evidences a change in the pK of polar groups, driven by progressive association of the dye molecules ( Fig. 6) (Stopa et al, 2010). The above phenomenon, though unusual, points to a new and interesting property of Congo red: higher concentrations promote association, thereby increasing acidity of the dye.…”

Influence of the electric field on supramolecular structure and properties of amyloid-specific reagent Congo red

“…Facilitated formation of amyloid-like protein aggregates in the presence of Congo red seems to confirm such a mechanism (Stopa et al 2010). Experimental and theoretical results supporting the suggested influence of the electric field on Congo red are presented in this article.…”

“…The ribbon-like micellar species composed of π–π stacked Congo red molecules are sensitive to the electric field, which generates significant electron delocalization affecting the supramolecular structure of species and the arrangement in solution, and finally influencing their interaction with proteins. Facilitated formation of amyloid-like protein aggregates in the presence of Congo red seems to confirm such a mechanism (Stopa et al 2010 ). Experimental and theoretical results supporting the suggested influence of the electric field on Congo red are presented in this article.…”

“…This means that rod-like or ribbon-like assemblies of this dye may bind proteins as single ligands, although they are composed of a number of dye molecules. These supramolecular ligands include several molecules of Congo red interacting with proteins directly, thus tightly bound, and also many attached indirectly (weakly bound) as the dye-dye associated micellar portion (Piekarska et al 2001 ; Stopa et al 2006 , 2010 ).…”

The use of supramolecular structures as protein ligands

“…Congo red and related dyes are an example (Fig. 1 ) [ 27 – 33 ]. Theoretical calculations enable modeling of such supramolecular structures, based initially on semi-empirical techniques and then using ab initio parameterization [ 17 , 27 ].…”