Structural differences between native Hen egg white lysozyme and its fibrils under different environmental conditions

• PCA of Raman data discriminates molecular structure of HEWL protein and fibrils.
• SD of scores in PCA plots determines variability in the structure within a species.
• Overall structure significantly differs for fibrils grown at different pH values.
• Overall structure of fibrils grown at different pH values in Cu(II) has similarity.
• Presence of Cu(II), inhibits the formation β-sheet component in HEWL fibrils.

The difference in molecular structure of native HEWL and its fibrils, grown at a pH value near physiological pH 7.4 and at a pH value just above the pI, 10.7 in presence and absence of Cu(II) ions, is discussed. We focus on differences between the molecular structure of the native protein and fibrils using principal component analysis of their Raman spectra. The overlap areas of the scores of each species are used to quantify the difference in the structure of the native HEWL and fibrils in different environments. The overall molecular structures are significantly different for fibrils grown at two pH values. However, in presence of Cu(II) ions, the fibrils have similarities in their molecular structures at these pH environments. Spectral variation within each species, as obtained from the standard deviations of the scores in PCA plots, reveals the variability in the structure within a particular species.

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