Misfolding of a polyalanine variant due to lack of electrostatic polarization effects

Folding of a polyalanine variant (A-AQ12 with the sequence Ac-[AAQAA] 2 -GY-NH 2 ) in pure water is studied with molecular dynamics (MD) simulation using AMBER fixed charge model and AHBC charge variation model, respectively. The results show that AMBER ostensibly misfolds A-AQ12 into a well-defined α-helix, while A-AQ12 remains a random coil in AHBC agreeing better with the experimental predication of low fractional helical content. The difference is most likely due to the different backbone solvation with and without the incorporation of electrostatic polarization in the simulations, which highlights the importance of electrostatic polarization in H-bonds dynamics of α-helix in water.