Examining the effect of the crown ether, 18-crown-6, on lysozyme fibrillation

Abstract

Proteins can form amyloid fibrils that are the cause of various degenerative diseases. In this work, we have investigated the potential of a crown ether, 18-crown-6, to arrest fibrillation in lysozyme. Initially, the kinetics of fibrillation were monitored using a Thioflavin T fluorescence assay. This assay revealed that the crown ether suppressed the fibrillation of lysozyme, which was reaffirmed by the absorbance in a Congo red assay. A Nile red fluorescence assay, an ANS binding assay, intrinsic fluorescence studies and steady-state fluorescence anisotropy also provided evidence that fibrillogenesis was inhibited by the crown ether. The formation of amyloid fibrils is characterized by the formation of β-sheet rich structures. Far-UV circular dichroism experiments revealed that the β-sheet content of the protein enhanced upon fibrillation but upon treatment with the crown ether there was a decrease in the total β-sheet content, which again testified the ability of 18-crown-6 to arrest fibrillogenesis. Atomic force microscopy imaging also suggested that the crown ether arrested lysozyme fibrillation. These results can be utilized for developing more effective anti-amyloidogenic agents.