Amyloid formation kinetics of hen egg white lysozyme under heat and acidic conditions revealed by Raman spectroscopy

Abstract

AbstractAmyloid fibrillation of proteins is a hallmark of neurodegenerative disease, accompanied by the formation of the organized cross‐β cores. This conformational transformation is considered to be related to the toxicity underlying the pathogenic mechanism. However, the exact conformational transformation kinetics of amyloid fibrillation are not fully understood. Herein, Raman spectroscopy was used to detect the transformation in the molecular structure of hen egg white lysozyme during amyloid formation under heat and acidic conditions (pH 2.0 and 65°C). The overall kinetics of the hen egg white lysozyme conformational change were investigated by analyzing five characteristic spectral fingerprints. The two N–Cα–C stretching bands at 899 and 935 cm−1 and the amide I band (at 1,640–1,680 cm−1) correlated to the lysozyme skeleton structure, whereas the band of the Phe amino acid group in side chains at 1,003 cm−1 and the two Trp residue bands at 760 and 1,340–1,360 cm−1 were associated with the tertiary structure. Based on these results, a four‐stage step‐by‐step transformation mechanism is first proposed to describe the exact kinetics of lysozyme amyloid fibrillation under heat and acidic conditions. This provides necessary information for physiologists to artificially control the amyloid formation of neurodegenerative disease patients.