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Journal of Experimental Biology 19,220-231 (1942)
Published by Company of Biologists 1942

Quantitative Aspects of the Disk-Sphere Transformation Produced by Lecithin

ERIC PONDER ¹

¹ The Nassau Hospital Mineola, L.I., N.Y.

1. The disk-sphere transformation produced in the mammalian red cell by lecithin can be studied quantitatively if the lecithin is added to the cells in the form of an isotonic sol, and if the preparations are examined between plastic slides and cover-slips.

2. The quantity of lecithin required to produce spheres from disks is approximately the same as that needed to form a monolayer at the red-cell surfaces.

3. The temperature coefficient of the lecithin disk-sphere transformation is small and positive.

4. The red-cell structure possesses a definite yield point, a certain quantity of lecithin being required to initiate the shape changes. Such yield points are characteristic of structures made up of large oriented molecules. The effect of fixation is to increase the yield point, the increase being a function of the concentration of the fixative.

5. The lecithin disk-sphere transformation can be reversed by the addition of lipoid solvents such as benzene, indol, chloroform, etc. The effect is a strictly quantitative one, the number of molecules required being about 10 times as great as that required to cover the cell surfaces, and somewhat more than 10 times as great as the number of lecithin molecules needed to bring about the disk-sphere transformation. The reversal of the transformation is usually followed by haemolysis, as most of the reversing substances are lysins.

6. The red-cell membrane is probably an ultrastructure of oriented molecules, about 200-500 A. thick, and seems to be able to exist in two metastable forms, the extended or discoidal form, and the contracted or spherical form. It is suggested that the seat of the forces which produce the extended form lies in the repulsions between the ionized hydrophilic groups of oriented cephalin molecules at the cell surface, and that the effect of a lecithin concentration at the surface is to diminish or abolish these forces. Reversing agents combine with the lecithin, and thus leave the repulsive forces able to establish the discoidal form again, at least temporarily.

7. Attention is called to the influence of the red-cell interior as modifying the effects of these essentially surface forces, particularly in reticulocytes, poikilocytes, and the nucleated red cells of the lower vertebrates.