Local changes in individual spider silk fibers from tubuliform and major ampullate glands of Trichonephila inaurata under varying humidity and tensile strain

Spider silk’s mechanics and environmental adaptability stem from a hierarchical architecture: crystalline β‑sheet nanodomains embedded in an amorphous protein matrix. While major ampullate (MA) silk’s structural responses to strain and environment have been studied, tubuliform (TU) silk — critical for egg sac construction and promising for biomedical uses — remains poorly understood. We investigate TU and MA silk from Trichonephila (T.) inaurata under varying relative humidity (RH) and mechanical strain using high‑resolution, spatially resolved nanobeam X‑ray diffraction (beam diameter ~100 nm). Increasing RH reduces Young’s modulus, yield strain, and yield stress in both silks, with TU silk being more humidity‑sensitive. Ultrastructural contrasts: At 30% RH, strain‑induced changes in TU are pronounced — decreases in lattice parameter a, increases in crystalline alignment, and reductions in coherent domain length L210 and lattice spacing d210 — whereas most strain responses weaken at higher RH. MA shows similar but smaller changes at 30% RH. Within the methods sensitivity at the probed length scale, zone‑averaged crystalline parameters were similar across the fiber diameter. The observed structural responses offer design templates for biomimetic materials. Future work should assess additional environmental variables and finer length scales to unlock spider silk’s potential as a model biomaterial. Major‑ampullate (MA) silk’s structural responses to strain and environment has been well studied, but tubuliform (TU) silk is poorly understood. This study investigates TU and MA silk under varying relative humidity and mechanical strain using high‑resolution nanobeam X‑ray diffraction. The authors would like to thank Maja Vasiljevic, Arno Frank, and Charbel Sakr for their assistance during the experiments conducted at the synchrotron facilities. Their support and expertise were instrumental in the successful completion of this work... [1637 chars]