Elastomeric behavior of the Bombyx mori fibroin (GAGAGS)n tandem motifs

The mechanical properties of tandems composed by a repetition of the -GAGAGS- motif characteristic of Bombyx mori silk fibroin are explored using molecular dynamics simulations. For each tandem the calculation starts from the configuration reached upon minimizing the initial energy and proceeds by determining representative stationary states obtained from molecular dynamics simulations at a temperature of T = 300 K. Subsequently, the tandems are loaded by applying force to the α-carbon atoms at their ends and the force-displacement curve is built from the force exerted on the tandem as a function of the end-to-end distance between these atoms. The results obtained reveal two regimes as a function of the number of repetitions: tandems with one or two repetitions do not show a characteristic elastomeric behavior, while the curves calculated for tandems with a number of repetitions of three or greater can be fitted to the theoretical curves of a freely jointed chain.