Comparative analysis of changes in the molecular structure of wool keratin after dyeing

The article presents a comparative analysis of structural changes in natural and dyed wool using Fouriertransform infrared spectroscopy (FTIR). The study objects included samples of undyed white and brown wool, as well as wool dyed with pink and pale blue dyes. The aim of the work was to evaluate the effect of the dyeing process on the secondary structure of α-keratin and the state of disulfide bonds. It was found that the undyed samples are characterized by a preserved α-helical conformation of keratin, which is confirmed by the position of the Amide I band in the range of 1631–1643 cm⁻¹ and the presence of stable S–S bonds in the region of 528– 561 cm⁻¹. No significant differences were found between white and brown wool. After dyeing, a shift of the Amide I band to 1625.99 cm⁻¹ is observed, indicating a partial change in the keratin structure. In this case, the pink dye has a moderate effect, while the pale blue dye causes pronounced structural changes, accompanied by oxidation of disulfide bonds and the appearance of a sulfonic acid band at 1055 cm⁻¹. The research results confirm that the chemical nature of the dye determines the degree of degradation of the keratin matrix. The FTIR spectroscopy method can be recommended for monitoring the structural integrity of wool fibers during technological processing.

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