Structural Phase Transition of Di-Block Polyampholyte

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Abstract
We have performed both conventional canonical molecular dynamics (MD) and multicanonical MD (MMD) simulations for a single di-block polyampholyte in vacuum to investigate possible structural phase transitions. The conventional canonical MD simulation for temperature T∗ > 0.05 gives reliable results, since these are independent of the initial conformation. The MMD simulation results for temperature T∗ > 0.05 are in good agreement with those of the conventional canonical MD simulation. Glassy-like states are obtained when quenched into temperatures below T∗ > 0.05 with a straight chain structure as an initial conformation. On the other hand a spherical double helical structure is obtained when the temperature is gradually lowered to T∗ > 0.01. Also we find a stretched double helical structure at T∗ ∼ 0.01 which changes to the spherical double helical structure by annealing and quenching.