Two approaches for modeling of the transmembrane
potential, as present in all eukaryotic cells, are examined in detail
and compared with each other. One approach uses an externally
applied electric field, whereas the other maintains an imbalance of
ions on the two sides of a membrane. We demonstrate that both
methods provide converged results concerning structural parameters
of the membrane which are practically indistinguishable from
each other, at least for monovalent ions. Effects of the electric field
on the detailed molecular structure of the phospholipid bilayer are
also presented and discussed. In addition, we achieve a considerable
speed-up of the underlying molecular dynamics simulations by
implementing the virtual interaction sites method for the Slipids
force field.