Auramine O as Potential Amyloid Marker: Fluorescence and Molecular Docking Studies

Abstract

The applicability of Auramine O to the detection and characterization of lysozyme and serum albumin amyloid fibrils has been assessed using the fluorimetric titration and molecular docking. The parameters of the dye binding to native and fibrillar proteins were estimated in terms of the Langmuir adsorption model. It was found that Auramine O displays the high affinity for amyloid fibrils, being of the same order of magnitude as that of the classical amyloid markers. The dye also showed greater fluorescence response to lysozyme fibrils and lower sensitivity to the native protein, than Thioflavin T. Furthermore, unlike Thioflavin T, Auramine O was able to detect the morphological differences between lysozyme and albumin fibrils due to the shifts in the position of the emission maxima of the fibril-incorporated fluorophore. The molecular docking studies revealed that Auramine O and Thioflavin T form the most stable complexes with the G54_L56/S60_W62 groove of lysozyme fibrils, running parallel to the fibril axis. The results obtained suggest the contribution of both hydrophobic and electrostatic interactions to the stabilization of the dye complexes with amyloid fibrils.