Effects of heat on secondary structures of silk fiber studied by ATR FT-IR microspectroscopy

Abstract

Attenuated total reflection Fourier transform infrared (ATR FT-IR) microspectroscopy has been employed to characterize the silk fiber. The character of silk spectrum contents of the four major peaks: amide A, amide I, amide II and amide III. The difference of spectra between the un-degummed and degummed silk fiber is the shoulder of amide I band at 1697 cm⁻¹. It was assigned to the anti-parallel β-sheet. The β-sheet is one type of secondary structure that shows the crystallinity. The crystallinity is related to the properties of silk fibers such as the softness and dyeability. Consequently, the properties of silk fiber are associated with the secondary structure. The secondary structure contained in the silk fiber could elucidate by curve fitting analysis. The amide I band of spectrum was used to determine the quantity of individual secondary structure. In this study, the controlled conditions are temperatures, times and quenching methods. According to the varied conditions, the quantity of secondary structure that was calculated from individual peak area has fluctuated. It is imply that it does not have significantly changes