Elastic properties, Young's modulus determination and structural stability of the tropocollagen molecule: a computational study by steered molecular dynamics.

The aim of this report is to investigate at microscopic level the elastic properties of a tropocollagen-like molecule submitted to linear traction along its longitudinal axis. For this purpose, we performed steered molecular dynamics (SMD) simulations for a wide range of spring constants in order to test the molecular response based on a two-spring model connected in series. An elastic behavior was observed in an elongation range of 2.5-4% of the molecular length, estimating an "effective molecular elastic constant" of 1.02+/-0.20 kcal/mol A2 in this region. Accordingly, a Young's modulus for the tropocollagen molecule of Y=4.8+/-1.0 GPa was calculated. The complex hydrogen bond network was traced along molecular dynamics (MD) and SMD simulations revealing a rearrangement of these interactions preserving the integrity of the molecular structure when submitted to traction. No evidence of the significant role attributed to water bridges for structural stability was detected, on the contrary facts pointed out that the hydrogen bond network might be the responsible.