DEPLETION OF MEMBRANE SKELETON IN RED-BLOOD-CELL VESICLES

A possible physical interpretation of the partial detachment of the me mbrane skeleton in the budding region of the cell membrane and consequ ent depletion of the membrane skeleton in red blood cell vesicles is g iven. The red blood cell membrane is considered to consist of the bila yer part and the membrane skeleton. The skeleton is, under normal cond itions, bound to the bilayer over its whole area. It is shown that, wh en in such conditions it is in the expanded state, some cell shape cha nges can induce its partial detachment. The partial detachment of the skeleton from the bilayer is energetically favorable if the consequent decrease of the skeleton expansion energy is larger than the correspo nding increase of the bilayer-skeleton binding energy. The effect of s hape on the skeleton detachment is analyzed theoretically for a series of the pear class shapes, having decreasing neck diameter and ending with a parent-daughter pair of spheres. The partial detachment of the skeleton is promoted by narrowing of the cell neck, by increasing the lateral tension in the skeleton and its area expansivity modulus, and by diminishing the attraction forces between the skeleton and the bila yer. If the radius of the daughter vesicle is sufficiently small relat ive to the radius of the parent cell, the daughter vesicle can exist e ither completely underlaid with the skeleton or completely depleted of the skeleton.