Microstructural Analysis of Wool Fibers by SEM Images of Their Cross-Sections Etched by Alkali Treatment

摘要

We found that scanning electron microscopy (SEM) of alkali-etched cross-sections of wool fibers provides characteristic images consisting of stitch patterns (SP) and amoeba patterns (AP) at the cortex and that both the SP and AP appearing as convex structures are originated from cell membrane complex (CMC), nuclear remnants, and intermacrofibril material. When the sample fiber had primarily been extracted with chloroform/methanol, the SP became disintegrated, because of the removal of free lipids from CMC, particularly from the β-layers. When the fiber had been extracted with chloroform/methanol/water, the SP was almost completely lost. These results suggested that the SP and AP are derived from the internal lipids and some non-keratinous proteins involved in the cortex and that the extraction of wool fibers with the mixed solvents should disrupt both the β- and δ-layers to increase the susceptibility of the CMC to the alkaline hydrolysis. The post-washing of the alkali-etched cross-section with ethanol made the SP and AP clearer. The agglomerated and scattered AP detected in the outlines of the cortical cells were shown to be originated from the nuclear remnants and the intermacrofibril material, respectively.