Predicting Penetration of Dyes into Living Cells by Means of an Artificial System.

Abstract

The penetration of dyes into the vacuoles of living cells of Nitella and Valonia proceeds as though the cell consisted of a non-aqueous layer lying between the external aqueous dye solution and the internal aqueous sap of the vacuole. On this basis it should be possible to predict the relative rate of penetration of dyes into the vacuoles of living cells if we know their rate of diffusion into the “vacuole” of an artificial system representing the 3 phases just mentioned.

To test this an artificial system was constructed consisting of a horizontal glass tube with 3 vertical arms. (1) To the left arm is added the dye solution (identical with the one in which cells are placed, i. e. sea water for Valonia and buffer solution for Nitella); (2) to the central arm is added chloroform (representing the non-aqueous layer of the living cell) until it fills the horizontal portions and the lower part of each upright tube. (3) Upon the chloroform in the right arm is poured some of the sap, artificial or freshly extracted from the living vacuole of Valonia or Nitella as the case may be (this will be called the artificial “vacuole”). Each one of these 3 phases is stirred by a separate glass stirrer entering through the corresponding upright arm. All the stirrers revolve at a uniform rate. Dye which penetrates into the chloroform at the phase boundary is rapidly distributed uniformly throughout the mass of chloroform. The rate of passage of the dye from the dye solution through chloroform into the sap (the artificial “vacuole”) is chiefly determined by the rate of diffusion at each phase boundary, which in turn is partly determined by the partition coefficient of the dye between the non-aqueous and the aqueous phase.