P R O T E I N S I N D E V E L O P M E N T
241
Euglobulin α + b 0-094 %
4
5
6
7
8
9
10 pH
FIG. 32. Change in viscosity of a solution of euglobulin a+b with p H value. The
sketches at the bottom correspond to the development of ventral ectoderm in Triturus
explants according to Holtfreter (1947). Protein denaturation corresponds to neural
induction; native protein to epidermal development.
E. Action of Vegetalizing Agents
Vegetalizing substances do not markedly affect the aforementioned
properties of proteins: the flow birefringence is not altered; the intensity of OH and phenolic group reactions is not increased (Arosio and
Bossi, 1954); and a monodisperse protein remains monodisperse after Li
treatment and shows little change in its s 20 (Fig. 40).
The action of vegetalizing substances becomes evident from another
type of experiment. We considered the action of a strong denaturing
agent such as urea on proteins treated with animalizing or vegetalizing
substances. Two samples were prepared of a solution of euglobulin
a + b from sea urchin eggs (Fig. 33). One was used as control (Tube 1).
An animalizing or vegetalizing substance sufficient in quantity to induce
an alteration in embryonic development was added to the other (Tube
2). For instance, LiCl as a vegetalizing agent was added to the protein solution to give a final concentration of 0-07 M. After incubation we assumed that the sample treated with LiCl was vegetalized.
From each sample we prepared two sub-samples of 5 ml each: 0-6 ml
of 1 M-KC1 were added to one sub-sample of each pair (Tubes 3, 5);
0-6 ml of 30% urea were added to the others (Tubes 4, 6); the viscosity
was read after incubation. Treatment with vegetalizing substances, as
mentioned before, induces an increase in viscosity. Now it is possible
to show something else: the viscosity decreases in the sub-sample with
urea; the rate of decrease in proteins treated with vegetalizing agents is
0-I50H
0-I25H
0·Ι0(Η
Q.
0-075H
0·05(Η
0-025^
241
Euglobulin α + b 0-094 %
4
5
6
7
8
9
10 pH
FIG. 32. Change in viscosity of a solution of euglobulin a+b with p H value. The
sketches at the bottom correspond to the development of ventral ectoderm in Triturus
explants according to Holtfreter (1947). Protein denaturation corresponds to neural
induction; native protein to epidermal development.
E. Action of Vegetalizing Agents
Vegetalizing substances do not markedly affect the aforementioned
properties of proteins: the flow birefringence is not altered; the intensity of OH and phenolic group reactions is not increased (Arosio and
Bossi, 1954); and a monodisperse protein remains monodisperse after Li
treatment and shows little change in its s 20 (Fig. 40).
The action of vegetalizing substances becomes evident from another
type of experiment. We considered the action of a strong denaturing
agent such as urea on proteins treated with animalizing or vegetalizing
substances. Two samples were prepared of a solution of euglobulin
a + b from sea urchin eggs (Fig. 33). One was used as control (Tube 1).
An animalizing or vegetalizing substance sufficient in quantity to induce
an alteration in embryonic development was added to the other (Tube
2). For instance, LiCl as a vegetalizing agent was added to the protein solution to give a final concentration of 0-07 M. After incubation we assumed that the sample treated with LiCl was vegetalized.
From each sample we prepared two sub-samples of 5 ml each: 0-6 ml
of 1 M-KC1 were added to one sub-sample of each pair (Tubes 3, 5);
0-6 ml of 30% urea were added to the others (Tubes 4, 6); the viscosity
was read after incubation. Treatment with vegetalizing substances, as
mentioned before, induces an increase in viscosity. Now it is possible
to show something else: the viscosity decreases in the sub-sample with
urea; the rate of decrease in proteins treated with vegetalizing agents is
0-I50H
0-I25H
0·Ι0(Η
Q.
0-075H
0·05(Η
0-025^