Correcting Isobaric Peptide Mass Shifts in Proteomic Fiber Quantification
Correcting isobaric peptide mass shifts in proteomic fibre testing prevents false wool detections and protects cashmere customs declarations from penalties.
Peptide Ratio Calibration Curves
Standard Preparation
Mass spectrometry analysis of protein-based fibers requires reference standards to quantify the proportion of different animal hair types in a blend. Constructing peptide ratio calibration curves involves testing series of known, pure reference mixtures ranging from pure cashmere to pure sheep wool. These samples are processed under identical conditions to ensure that the recovery rate remains constant across all test runs.
The ratio of the chosen marker peptides is plotted against the known blend composition to create a linear reference. This reference allows the laboratory to evaluate unknown commercial textile samples.
Enzymatic Digestion
Chemical breakdown of the fiber proteins uses specific enzymes to release the target peptides. Trypsin cuts the keratin or fibroin chains at precise amino acid locations to produce predictable fragments. The relative abundance of these fragments is measured by the detector.
This abundance reflects the original species distribution in the fiber blend.
Quantitative Analysis
Liquid chromatography separates the digested fragments before they enter the mass spectrometer. The spectrometer measures the mass-to-charge ratios of the peptide ions to identify their source. Comparing the peak area ratios to the reference curve yields the percentage of each fiber type.
Blended Accuracy
Accurate curve construction is crucial for identifying fraudulent labeling in high-value garments. This method can detect substitution levels down to low percentages. This protects brand integrity.