Inhibition of amyloid fibrillation and destabilization of fibrils of human γD-crystallin by direct red 80 and orange G

Abstract

Inhibition of amyloid fibril formation by a lens protein namely human γD-crystallin (HGD) under stressful conditions was targeted by using some small molecules like direct red 80 (DR), orange G (OG) and rhodamine B (RH). The protein itself was found to form matured fibrils after 48h of incubation at pH 3.0 at 37°C. Various fluorescence based assays (thioflavin T assay, ANS binding assay, intrinsic Trp fluorescence determination), circular dichroism and microscopic imaging techniques were used in the inhibition studies. Above studies unequivocally proved that DR had acted as the most potent inhibitor among these molecules and it was little better efficient than OG. RH had shown a moderate inhibition of HGD fibrillation. Microscopic images from fluorescence microscopy and transmission electron microscopy also substantiated our spectroscopic observations. These small molecules were not only capable to restrict the fibrillation, but they were also able to disassemble the mature and premature fibrils of HGD. Hydrophobic and aromatic interactions between the inhibitor molecules and partially unfolded HGD are likely to be responsible for exhibiting inhibition of protein fibrillation.