Chemical Alteration
Covalent modification of amino acid residues in keratinous proteins occurs during the heating and alkaline washing of animal hair. In industrial scours and dye baths, asparagine deamidation leads to the conversion of asparagine into aspartic acid or isoaspartic acid. This chemical drift alters the net charge of the protein backbone.
Degradation Marker
Identifying the extent of this reaction provides a measure of thermal and chemical exposure in cashmere or wool lots. Because asparagine deamidation proceeds at a known rate under specific temperatures, the ratio of modified to unmodified peptides indicates whether a batch of premium yarn has been over-processed. Excessive exposure during scouring or dyeing degrades the tensile strength of the hair, which makes the fiber brittle.
Analytical Influence
Mass spectrometry must account for the resulting mass increase of approximately one dalton per reaction site. When performing quantitative analysis on premium blends, ignoring asparagine deamidation yields incorrect protein concentration estimates. Chromatographic separation shifts slightly due to the modification, requiring adjusted elution windows.
Processing Impact
Control of the scouring bath temperature limits this degradation to acceptable baseline levels. Mill specifications often dictate a maximum deamidation percentage to ensure that the protective outer cuticle of the fiber remains intact. Higher levels correlate with poor spinning performance.
