  An effect of membrane surface charge on mechanical properties of the
phospholipid bilayer membrane and pores formation is considered. It is shown
that the outer and inner surfaces of the phospholipid membrane is always
subject to tension, regardless of magnitude and sign of the charges on its
surface. This is due to the fact that the Debye length of the extracellular and
intracellular electrolyte is always much smaller than the thickness of the
membrane, and accordingly the electric field on the outer surface of the
membrane is always much larger than the field inside the membrane. This result
contradicts the generally accepted notion that a charged phospholipid membrane
is similar to a charged capacitor in a dielectric medium and it is always
subject to compression. Phospholipid bilayer membrane will be subject to
compression only in a very weak electrolyte (~1mM/L), when Debye length is
larger than the membrane thickness. It is also shown that the membrane surface
charges lead to pore compression when the pore radius is larger than the Debye
radius and to the stretching in the opposite case. Difference in the
coefficients of surface and edge tension of phospholipid cell membranes can be
explained by taking into account the cell membrane surface charge. Simple
experiments are proposed to test the influence of the cell membrane surface
charge on its mechanical properties.
