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

Abstract

Amyloid 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.

Recent advances in linear and nonlinear Raman spectroscopy. Part XIV

“…They foresee this statistical technique leading to a widening of the adoption of Raman as a monitoring tool in a field of biofluid analysis. Xing et al [ 58 ] studied the amyloid formation kinetics of hen egg white lysozyme under heat and acidic conditions using Raman. They proposed a four‐stage step‐by‐step transformation mechanism to describe the exact kinetics of lysozyme amyloid fibrillation under heat and acidic conditions, and this provides necessary information for physiologists to artificially control the amyloid formation of neurodegenerative disease patients.…”

Molecular Dynamics Study on the Effects of Charged Amino Acid Distribution Under low pH Condition to the Unfolding of Hen Egg White Lysozyme and Formation of Beta Strands

“…Lysozymes are a family of globular enzymes in the immune systems of animals. A lysozyme molecule is a single polypeptide of around 130 residues that can partially hydrolyze the peptidoglycans of gram-positive bacterial cell walls [1,2]. Lysozyme is one of the protein types that are associated with the formation of amyloid fibrils under some specific conditions.…”

“…Unfolding and refolding of HEWL during amyloidosis could be accelerated under a high temperature and acidic condition. A previous study showed that amyloid fibrils were formed when incubating HEWL under the temperature of 65 °C and pH 2 for 196 hours [1].…”

“…Under an elevated temperature and acidic condition, AFM could provide images of lysozyme aggregation at various incubation times by depicting the time-dependent sizes of self-assembled spheroidal oligomers. The changing of both the secondary and tertiary structures of the aqueous lysozyme could also be observed by the shifting of Raman spectra in the range of 650 – 1875 cm -1 from its native state [1]. Signals from EIS spectroscopy are highly sensitive to the changing of both secondary and tertiary structures of the protein due to their unique charge transfer resistances (Rct) [21].…”

“…Signals from EIS spectroscopy are highly sensitive to the changing of both secondary and tertiary structures of the protein due to their unique charge transfer resistances (Rct) [21]. These methods, along with dynamic light scattering, size exclusion chromatography, transmission electron microscopy (TEM), Fourier transform-infrared (FT-IR) spectroscopy, the surface plasmon resonance (SPR) [1,22,23], have their own advantages but still lack understanding in the molecular details of protein structural changes.…”