Fig. 3

Morphology of spider silk and silkworm glands. Schematic diagram of silk glands with reported pH and ion gradients. A In the spider major ampullate gland, chaotropic ions are replaced by kosmotropic ions, which induce phase separation, while a gradient of decreasing pH induces the dimerization of NTD, which promotes fibril formation. B In the B. mori silk gland, the higher concentration of Ca²⁺ ions in the lumen in the PSG and MSG prevents premature fibrillation, while in the ASG, the pH decrease and localization of metal ions to the epithelial cells subsequently induce phase separation and fibril formation