Nucleation and Growth of Macrofibrils in Trichocyte (Hard-Alpha) Keratins

The study explored the nucleation and growth mechanisms of macrofibrils in trichocyte keratins, focusing on the differences in intermediate filament (IF) packing in the paracortex and orthocortex of fine Merino wool. Two types of macrofibril structures were identified: quasi-hexagonal packing in the paracortex and cylindrical sheet packing in the orthocortex. The research suggested that sheet formation is crucial in both types of macrofibril assembly, with intersheet interactions contributing to structural differences. The study also examined the tilt of IF in orthocortex macrofibrils, proposing models to explain these observations based on electron micrograph analysis and X-ray diffraction studies.