Amyloids, Congo red and the apple-green effect.

This paper attempts to find evidence of the previously proposed opinion that amyloids complex with Congo red molecules which preserve their supramolecular organization. As evidence of the overpowering tendency of Congo red molecules to self-assemble, we present an increasing acidity of molecules that follows increasing concentration of the dye, and a highly notable nonlinear increase in absorbance in the UV band (300-400 nm). This effect is analyzed in a model where the amyloid fibril is simulated by polyvinyl alcohol, providing a scaffold to stabilize a long Congo red micelle.

Force-field parametrization and molecular dynamics simulations of Congo red.

Congo red, a diazo dye widely used in medical diagnosis, is known to form supramolecular systems in solution. Such a supramolecular system may interact with various proteins. In order to examine the nature of such complexes empirical force field parameters for the Congo red molecule were developed.