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.
Highlights
С помощью методов флуориметрического титрования и молекулярного докинга проведена оценка возможности использования аурамина О для детектирования и характеризации амилоидных фибрилл лизоцима и сывороточного альбумина
These dyes belong to the molecular rotor family due to the internal rotation of their fragments upon excitation, followed by the transition from the fluorescent locally excited (LE) state to the nonfluorescent twisted internal charge transfer (TICT) state [19,20]
The above mechanism was suggested to underlie the high sensitivity of Thioflavin T (ThT) to amyloid fibrils due to the dye embedding into the fibril grooves, running parallel to the fibril axis, giving rise to significant increase in the potential energy of relative rotation of the benzothiazole and phenyl moieties [21]
Summary
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. КЛЮЧЕВЫЕ СЛОВА: аурамин О, тиофлавин Т, амилоидный маркер, константа ассоциации, квантовый выход флуоресценции, молекулярный ротор, лизоцим, сывороточный альбумин, амилоидные фибриллы. КЛЮЧОВІ СЛОВА: аурамін О, тіофлавін Т, амілоїдний маркер, константа асоціації, квантовий вихід флуоресценції, молекулярний ротор, лізоцим, сироватковий альбумін, амілоїдні фібрили. The above drawbacks of ThT strongly suggest the necessity of designing the novel amyloid markers To exemplify, another dye, Auramine O (AuO) has been successfully employed to detect insulin aggregates [19]. Further investigation of albumin fibrillization and its effects on the amyloid fibril formation by the other proteins and peptides may prove of importance for the improvement of antiamyloid strategies
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