Analysis of magnesium membraneous effects: binding and screening.

There are two categories of electrostatic interactions between cations and negatively membrane charged surfaces. First, there is the usual type of electrostatic binding where the cations complex to anionic surface moieties. There exists, however, a second type of association, often referred to as screening. In this case, the cations remain mobile, being held loosely in a diffuse layer close to the surface. When divalent cations are added in the bathing medium, a screening effect (S) induces a reduction of Gt, a binding effect (B) induces an increase of Gt and a screening-binding effect (S-B) induces a reduction, then an increase, of Gt. In the isolated human amnion, among the magnesium salts studied, only MgCl2, Mg citrate and Mg acetate have a S-B effect on both faces of the membrane.