Abstract
In the preparation of natural globin by the method described in the preceding paper the solution obtained is too dilute for certain purposes. It has been found impossible to concentrate the solution by any of the usual methods without great loss as the globin is very susceptible to denaturation by a variety of agents. Finally a method is found which works well for globin and should be applicable to any protein solution.
The principle of the method is simple, but it does not seem to have been employed as a laboratory technique. The protein solution is concentrated by dialysis against a concentrated solution of another protein or some other substance which cannot diffuse through the membrane. Fresh egg white serves this purpose very well. It is convenient to insert into the tube a rubber stopper with a large hole. The tube is tied to the stopper with a string which serves for hanging the tube.
A collodion tube such as is used for dialysis is prepared. Transfer to the tube a measured volume of water and place the tube in about 10 volumes of fresh egg white. The dialysis is allowed to take place in the ice chest.
After 24 hours the water in the tube will have decreased to a small fraction of the original volume. This water is removed with a pipette and tested for protein. If the test is negative, the collodion tube is suitable for use.
The dilute protein solution to be concentrated is transferred to the tube and dialyzed against egg white. As the solution becomes concentrated more of the dilute solution is added to it from time to time. The dialysis is continued with frequent change of the tgg white until the desired concentration is reached.
Get full access to this article
View all access options for this article.