Evidence by infrared spectroscopy of the presence of two types of β-sheets in major ampullate spider silk and silkworm silk

摘要: The major ampullate (MA) silk of spider is known to be composed oriented β-sheet nanocrystals dispersed within an amorphous matrix. presence interphase has also been proposed, but it not reported for the fibroin silkworm Bombyx mori (B. mori). To obtain quantitative information regarding this third phase, deuteration B. and Nephila clavipes MA probed by attenuated total reflection infrared spectroscopy. spectral decomposition amide II region allowed determination level orientation content different secondary structures. data reveal that, in addition domains, part β-sheets deuterated upon immersion D2O both silks. D2O-inaccessible are associated with crystallites, while D2O-accessible ones. It found that former slightly more along fiber axis than latter ones, which suggests located at ends crystals. similar (50 ± 4%) (46 4%). However, 27 3% compared 8 silk. These suggest around 5 amino acids 9 would involved β-sheets. higher amount believed contribute its toughness.