Identification and classification of silks using infrared spectroscopy

Abstract

Lepidopteran silks number in the thousands and display a vast diversity of structures, properties, and industrial potential. To map this remarkable biochemical diversity, we present an identification and screening method based on the infrared spectra of native silk feedstock and cocoons. Multivariate analysis of over 1214 infrared spectra obtained from 35 species allowed us to group silks into distinct hierarchies and a classification that agrees well with current phylogenetic data and taxonomies. This approach also provides information on the relative contents of sericin, calcium oxalate, phenolic compounds, poly-alanine and poly(alanine-glycine) β-sheets. It emerged that the domesticated mulberry silk-moth Bombyx mori represents an outlier compared to other silk moth taxa in terms of spectral properties. Interestingly, Epiphora bauhiniae was found to contain the highest amount of β-sheet reported to date for any wild silk-moth. We conclude our approach provides a new route to determine cocoon chemical composition and in turn a novel, biological as well as material, classification of silks.