‎Laboratory‎ > ‎Dialysis

In this experiment we observed the dialysis. The principle of dialysis is that the small molecules can penetrate through the pores of semi-permeable membrane toward the buffer solution while large molecules cannot. By using this method we separated glucose from starch and cystein from Bovine Serum Albumin (BSA). So the small molecules (glucose and cystein) were collected in buffer side and large molecules (starch and BSA) were kept in the bag. Then we tested the buffer solutions and the solutions in the bag with the reagents to decide if the separation process was completed successfully or not.

The samples taken from the buffer solution and the solution inside of the bag of starch- glucose mixture was tested with Lugol’s solution and Benedict reagent. Lugol’s solution is used to observe the presence of starch since the colour changes from yellow to blue-black in the presence of starch. The result showed that there was starch in the bag but there was not any in the buffer. This result was expected. Then Benedict reagent was used which changes colour from blue to red in the presence of glucose. The result showed that there was glucose in the buffer but there was not any in the bag. This result was also expected. So according to the results we can say that the glucose-starch separation was successful.

The samples taken from the buffer solution and the solution inside of the bag of BSA- cystein mixture was tested with Biuret reagent and Ninhydrin solution. Biuret reagent is used to observe the presence of protein (BSA) since the colour changes from blue to purple in the presence of protein. The result showed that BSA was found in both buffer and bag. This result was not expected because BSA cannot pass from the pores of membrane. So it should not be found in the buffer. The reason of that may be not to properly tying the both ends of cellulose membrane bag. Ninhydrin solution is used to observe the presence of amino acid (cystein) since the colour changes from blue to violet in the presence of amino acid. The result showed that there was cystein present in the buffer but there was not any in the bag. So we can say that cystein separation was successful.

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