Membrane Electrostatics
Consider a phospholipid bilayer membrane consisting of a mixture
of 90% uncharged lipid and 10% singly charged acid lipid. Assume 68
Å^2 surface area per lipid head group, and assume further that the
charged lipids are uniformly distributed and immobile. The membrane
is in contact with an aqueous solution of NaCl at 25 °C. The salt
concentration is C_∞ = 100mM.
(a) Calculate charge per unit surface area of the membrane.
(b) Calculate the surface potential of the membrane.
What is the electrostatic energy (in k_B*T units) of binding to
the membrane of a trivalent positive ion such as spermidine (a
biologically active polyamine) assuming that:
(c) Binding occurs at the membrane surface?
(d) Owing to steric factors the charges of the bound spermidine
stay in the water 5 Å
Consider a phospholipid bilayer membrane consisting of a mixture of 90% uncharged lipid and 10% singly charged acid lipid. Assume 68 A2 surface area per lipid head group, and assume further that the charged lipids are uniformly distributed and immobile. The membrane is in contact with an aqueous solution of NaCl at 25 oC. The salt concentration is Coo 100mM Ca) Calculate charge per unit surface area of the membrane. (b) Calculate the surface potential of the membrane. What is the electrostatic energy Gin kBT units) of binding to the membrane of a trivalent positive ion such as spermidine (a biologically active polyamine) assuming that: (c Binding occurs at the membrane surface? (d) owing to steric factors the charges of the bound spermidine stay in the water 5 A distant from the membrane surface?