Controlling amyloid fibril formation by partial stirring

Many proteins undergoe self-assembly into fibrillar structures known as amyloid fibrils. During the self-assembly process, related structures known as spherulites can be formed. Herein we report a facile method where the balance between amyloid fibrils and spherulites can be controlled by stirring of the reaction mixture during the initial stages of the self-assembly process. Moreover, we report how this methodology can be used to prepare non-covalently functionalized amyloid fibrils. By stirring the reaction mixture continuously or for a limited time during the lag phase, the fibril length, and hence the propensity to form liquid crystalline phases, can be influenced. This phenomena is utilized in order to prepare films consisting of aligned protein fibrils incorporating the laser dye Nile red. The resulting films display polarized Nile red fluorescence.