Molecular Dynamics Study of the Structure and Mechanical Properties of Spider Silk Proteins.

Spider silk is renowned for its exceptional toughness, with the strongest dragline silk composed of two proteins, MaSp1 and MaSp2, featuring central repetitive sequences and nonrepetitive terminal domains. Although these sequences to spider silk's strength and toughness, the specific roles of MaSp1 and MaSp2 at the atomic level remain unclear. Using AlphaFold3 models and molecular dynamics (MD) simulations, we constructed models of MaSp1 and MaSp2 and validated their stability. Steered molecular dynamics (SMD) simulations showed that MaSp2 resists lateral stretching, whereas MaSp1 exhibited better extensibility. During longitudinal stretching, MaSp1 formed cavities, whereas MaSp2 stretched uniformly. Hydrogen bonds involving GLN and SER in MaSp1 were strong, whereas those involving Tyr307 were prone to breakage, potentially weakening toughness. These results indicate that MaSp1 enhances extensibility, whereas MaSp2 imparts greater toughness. This study offers key molecular insights into spider silk's strength, informing the design of artificial fibers.