Nonlinearity of proteinoids, which is synthesized simulate primitive proteins, was investigated to discuss spontaneous motion in the origin of life. We prepared a heated solution of proteinoids with different solubility and an unheated solution and dropped the mixed solution on ethanol-containing oleic acid. Heated mixed-proteinoids droplets moved spontaneously. To compare the change in the interaction of mixed proteinoids with that before heating, the Hill coefficient during dissolution was measured. It clarified that the Hill coefficient of the hybrid proteinoid decreased significantly compared to that before heating. This result suggests that the cooperativity between proteinoid molecules has changed.
The presence of Marangoni convection was confirmed in the case of mixed proteinoid droplets, but no convection was seen in others. The change in surface tension of droplets was largest for the mixed proteinoid droplets. In contrast, the adhesion force was the smallest for the mixed proteinoids. The droplets of the mixed proteinoids had the largest driving force and the smallest resistance force, showing that it was the most suitable for motion.
In conclusion, spontaneous motion of droplets with nonlinearities was realized using amino acid proteinoid. This result shows that the function of spontaneous motion was appeared by the denaturation of multiple compositions of proteinoid.