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The dating of silk textiles can be problematic for experts but a team of researchers at the Smithsonian Institute has developed a new method with this as their main objective.
The dating of silk textiles can be problematic for experts but a team of researchers at the Smithsonian Institute has developed a new method with this as their main objective.1
They have introduced a new capillary electrophoresis–mass spectrometry (CE–MS) technique based on amino acid racemization rates. As the amino acids making up proteins are chiral, being either left- or right-handed, or L or D, Moini and her team utilized aspartic acid, which has one of the fastest switching rates, a half-life of 2500 years, and separated the two enantiomers in a CE buffer containing a chiral molecule. They then determined their proportions using MS. Analysis required only 100 µg of silk fibre, which was digested with hydrochloric acid at 110 °C. This non-destructive method took only 20 minutes, consumed only nanolitres of the amino acid mixture and provided both amino acid composition profiles and D/L ratios for 11 amino acids.
Moini and her team were able to test this method on several silk fabric selections and found that the measured ratio of left- and right-handed aspartic acids reflected the historical ages of the selected fabrics.
1. Mehdi Moini et al., Anal. Chem., 83(19), 7577–7581 (2011)