Analysis of spider silk in loading-unloading cycles using Raman spectroscopy based on molecular bioinformatics of spidrion

Abstract

The mechanical properties of spider silk result from its organization at various levels, including the amino acid sequence, protein structure, protein assembly and full-hierarchical microstructure. However, the relatively few reports that contain an analysis of the motifs along the full-length of the sequences, and of the evolution of their secondary structure when the fiber is subjected to mechanical load, render difficult the task of relating sequence, microstructure and properties for this material. In this study, we identified seven spider major ampullate gland silk proteins of Argiope bruennichi, determine their full-length amino acid motifs, simulated the repeated stretching of spider major ampullate gland silk (MAS) in the natural environment, verified the stability of its mechanical properties, and established the evolution of its protein structure by semi-quantitative analysis of Raman spectroscopy. After stretching at different strains, MAS can recover previous mechanical behavior and exhibit excellent mechanical memory in terms of longitudinal stretching. It is also shown that MAS maintain its mechanical properties through a precise adjustment of protein structure, secondary structure transformation and reconstruction. This study shows that the repeated stretching characteristics of spider major ampullate gland silk may be a post-processing adjustment way that, in combination with its molecular organization, may bring a new inspiration for the relation of sequence-structure-property.