2022 Volume 78 Issue 9 Pages 153-160
Though species of insect cocoons were partly discriminated by the shape and colour, silk was not impossible to identify them because no DNA remained on them. The method using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was established for the identification of cocoons and silks of the silkworm (Bombyx mori), Eri-silkworm, and wild moth based on the cleaved peptide mass fingerprints (PMFs). This method could be evaluated the oldness based on the peak shift by post-translational amino acid modifications. Insect cocoons and silk fibers were partially hydrolysed by diluted formic acid at room temperature (RT) and the PMFs were used to identify insect species, races, and qualities by MALDI-TOF MS. Silk proteins could be hydrolysed limitedly by acid at RT and several kinds of cleaved peptide fragments were obtained from silk. Cocoons and silk could be analysed by MALDI-TOF MS showing the PMFs during the degumming process and differences among races and species. In addition, peak shifts were observed in old silk comparing newly spanned silk. MALDI biotyping using acid hydrolyzed peptides against cocoons and silks could identify the insect species and discriminated silkworm races and oldness based on the PMFs and by their peak shifts.
