Order, Disorder and Re-Order State of Lysozyme: Aggregation Mechanism by Raman Spectroscopy

Lysozyme, like many other well-folded globular proteins, under stressful conditions produces nano-scale oligomer assembly and amyloid-like fibrillar aggregates. Engaging Raman microscopy, we made a critical structural analysis of oligomer and other assembly structures of lysozyme obtained from hen egg white and, provided a quantitative estimation of protein secondary structure in different states of its fibrillation. A strong amide I Raman band at 1660 cm-1 and N-Cα-C stretching band at ~930 cm−1 clearly indicated the presence of a substantial amount of α-helical folds of the protein in it’s oligomeric assembly state. In addition, analysis of amide III region and Raman difference spectra suggested ample presence of PPII like secondary structure in these oligomers without causing major loss of α-helical folds which is found in the case of monomeric samples. Circular dichroism study also revealed the presence of typical α-helical folds in the oligomeric state. Nonetheless, most of the Raman bands associated...