Mass Spectrometry SRM Calibration Protocols for Cashmere Wool Blends
Selected reaction monitoring mass spectrometry quantifies cashmere wool blends down to one percent using species-specific tryptic keratin peptides.
Keratin Type I and Ii Isoforms
Protein Categorization
Mammalian intermediate filament proteins are divided into acidic and basic-neutral groups that associate to form the primary structural network of animal fibers. Within these structural groups, keratin type i and ii isoforms co-assemble in equal ratios to build the microfibrils that give wool and cashmere fibers their strength and elasticity. These proteins represent the vast majority of the extractable mass from animal hair.
Sequence Variation
Point mutations and minor differences in amino acid sequence between species are preserved in these structural proteins. In cashmere and wool fibers, keratin type i and ii isoforms display subtle variations that reflect the evolutionary distance between goats and sheep. These variations are localized in specific variable domains of the protein chain.
Analytical Biomarker
Proteomics-based assays exploit these sequence differences by targeting the specific peptide regions that are unique to each species. When digested with trypsin, the unique sequences of keratin type i and ii isoforms yield signature fragments that are used for quantitative analysis. This allows testing houses to detect sheep wool admixture in high-value cashmere.
Textile Assessment
Textile laboratories utilize these structural differences to verify high-cost yarn shipments before they enter bulk garment production. In particular, identifying the unique patterns of keratin type i and ii isoforms helps garment brands confirm that they are getting the high-grade materials they paid for. This check protects the supply chain from fraudulent substitution and maintains consumer trust.
The test reports generated by these studies are used to support customs declarations and product marketing claims globally.