Li, Hui; Fan, Jianfen F.; Li, Rui; Yu, Yi; Yan, Xiliang L.
Molecular dynamics studies on the influences of a gradient electric field on the water chain in a peptide nanotube
JOURNAL OF MOLECULAR MODELING, 20 Art. No. 2370, AUG 2014

The structure and transportation characteristics of the water chain inside a 8xcyclo-(WL)(4) peptide nanotube (PNT) were simulated under a gradient electric (GE) field. The gradient was defined by the ratio of a constant (E-a) and the z-directional length (L-z) of the simulation box. E-a varies from 0.0 to 0.9 V nm(-1). As the gradient increases, the probabilities of finding two water molecules in an alpha-plane zone and three in a midplane region increase. To accommodate more water molecules, the axial array of channel water molecules becomes more compact. Meanwhile, the H-bonded network between the channel water is greatly intensified when E-a increases from 0.3 to 0.9 V nm(-1). Nevertheless, the proportion of strong H-bonds does not increase significantly following the formation of a more compact axial array of water molecules. When E-a reaches 0.9 V nm(-1), the water molecule in an alpha-plane zone may be dragged by its neighboring water molecules into the midplane region, resulting in a significant deviation from the channel axis. With the augment of the gradient, the dipoles of channel water are gradually oriented along the tube axis in the sequence from gap 1 to 7, namely along the direction of the electric field. Nevertheless, even when E-a reaches 0.9 V nm(-1), the dipole orientation of the channel water is not complete, and dipole flips still occur in gap 7. Under a GE field, the rightward and leftward hopping rates of channel water are no longer equal to each other, i.e., channel water performs an asymmetric transportation.

DOI:10.1007/s00894-014-2370-x

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