Cell compartments coacervation

Fig. 37. Complex coacervation of a mixture of gelatin and gum arabic sols enclosed in cell compartments, a The complex coacervate has separated out as drops they coalesce with each other and flow on contact with the wall over it with the formation of a coacervate layer adjacent to the wall.

Fig, 38. Different ways along which the final morphological position of the complex coacervate gelatin-gum arabic in the cell compartments can be reached (see text), a 0.01 N acetic acid is passed through the cuvette at 35° C. b 0.01 N acetic acid, containing 40 m. eq. p. 1 NaCl is passed at 35°, followed by 0.01 N acetic acid without salt, c cold 0.01 N acetic acid is passed through the cuvette and the temperature is gradually rised. 

Fig. 39. Topographical position of the three coexisting liquids (after complex coacervation of a gelatin 4- arabinate 4 nucleate sol mixture) in the cell compartments of an artifical tissue (schematic). The G 4- N -h a coacervate (grey) lies embedded in the G + A + n coacervate adjacent to the wall. This latter encloses a central vacuole (equilibrium liquid).

The cell walls are permeable to some relatively low molecular colloids so that they are more or less rapidly washed out from the cell compartments. This is for example the case with yeast nucleic acid, as a result of which the composition in a cell containing G -I- N -F A changes continually. As the coalescence of very fine coacervate drops to the states represented in Fig. 39 requires a comparatively long time and as the composition of the content of the cell must lie within narrow limits (c.f. Ch. X, 2t, Fig. 33, p. 380) the realisation of satisfactory morphological pictures meets with serious difficulties and indeed has only succeeded one or two times. Moreover the states of Fig 39 do not represent the final equilibrium but in the end the coacervate G -h N f A disappears completely through continued loss of nucleic acid. 

As already stated in 5 a (p. 467) coacervates in general wet the celloidin membranes of the prismatic cells. This also holds for the coacervate which is produced after accumulation of a basic dye (for example toluidine blue) in the cell compartments filled with gum arabic sol. In the final state it wets the cell walls and lies spread out in a thin layer over them. ... 

By passing a very dilute salt solution (e.g. NaCl 5 m. aeq. p. 1) over (suppressing action on the dicomplex coacervate dye cation —arabinate) the dye is gradually washed out again and the ultimate equilibrium state will be that all coacervate has disappeared from the cell compartments and the latter are again filled with a gum arabic sol. 

The latter draws away from the cell walls and rounds itself off, after which the coacervate proceeds as separate spheres into the interior of the cell compartments (see Fig. 43 a b c). 

Thus already in Fig. 43c a certain amount of the arabinate toluidine blue coacervate is in solution, which follows from the darker background shade of the three cell compartments considered as compared to the same three in Fig. 43b. 

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