. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. STRUCTURE OF THE PLASMA MEMBRANE direction, the anions of the surrounding solution can be exchanged against the anions of the interior of the cell. And now the question arises, how it is to be understood, that in the case of the collodion membrane the pore permeability is limited to the cations and, in the case of the red blood corpuscles, to the anions. Michaelis had already turned his mind to the fact that the substance of the cation-permeable membrane itself is negatively charged, and he connected this idea with the well-

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. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. STRUCTURE OF THE PLASMA MEMBRANE direction, the anions of the surrounding solution can be exchanged against the anions of the interior of the cell. And now the question arises, how it is to be understood, that in the case of the collodion membrane the pore permeability is limited to the cations and, in the case of the red blood corpuscles, to the anions. Michaelis had already turned his mind to the fact that the substance of the cation-permeable membrane itself is negatively charged, and he connected this idea with the well-
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Image ID: RHMWAG
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. STRUCTURE OF THE PLASMA MEMBRANE direction, the anions of the surrounding solution can be exchanged against the anions of the interior of the cell. And now the question arises, how it is to be understood, that in the case of the collodion membrane the pore permeability is limited to the cations and, in the case of the red blood corpuscles, to the anions. Michaelis had already turned his mind to the fact that the substance of the cation-permeable membrane itself is negatively charged, and he connected this idea with the well-known membrane studies of Bethe and Toropoff 7 and the experiments on the reversal of membrane potentials in gelatine discs, which have been established by Matsuo in my own laboratory.8 As a matter of fact it can be proved that this idea is right. There exists a relation between the electric charge of the membrane material and the faculty of the ions with opposite electric charge to pass. In my laboratory Mond succeeded in demonstrating that if the negative charge of the collodion is changed to a positive charge by addition of a basic dye, for instance by rhodamin, the membrane thus formed, instead of being exclusively cation-permeable is changed into a membrane of selective anion- permeability.9 Table III illustrates the resulting conditions. TABLE III Membrane Potentials in Rhodamin-collodion Membranes — Cl 0.1M NaCl ^~ 0.1M NaCl 0.1M NaCl 0.1M NaCl 0.1M NaCl 0.1M NaCl SCN > I > Br > Cl > SO4 Cations without effect The dotted arrows show the direction of the movement of the chlorine ions; their length is a measure of the potential dependent on the velocity of the ions. The arrows drawn refer in a corresponding manner to the anions of the opposite side of the membrane. The electromotive forces decrease from -f- 60 millivolts to - - 3.8 millivolts along the series of anions: thiocyanate, iodine, bromine, chlorine, sulfate. The cations are without any effect. The m

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