Question

Suppose you used a paper chromatography method to separate all the amino acids, but aspartate (aspartic acid) and glutamine were not resolved. Which of the following would be your best next step to separate these 2 amino acids? There may be more than one possibility. Pick one choice and justify it.
Choices: (paper electrophoresis at pH 2) (paper electrophoresis at pH 12) (paper chromatography)
(trypsin treatment) (paper electrophoresis at either pH).

Answer 1

• Aspartic acid is a negatively charged amino acid while glutamine is a neutral amino acid.
• In the paper electrophoresis process the desired ph of the buffer solution is needed for separating the amino acids.
• The PI of the aspratate is 2.77 while it is 5.65 for glutamine so that in this ph range both will not move in the electrophoresis respectively.
• So at the ph 2 as it is nearly equal to the pi of the aspartate it will not be better to resolve aspartate. So that electrophoresis at ph 12 can resolve both at the positive end of the electrode easily.
• At ph 12 the aspartate will have a higher negative charge in comparision to the glutamine. Both will move towards the positive end of the electrode.
• As the higher will be the ph from the pi value the charges will be more negative.
• In the ph 2 choice the glutamine will move towards the negative end as it will be positive as the pi is higher than the ph. but as the aspartate PI is almost 2.77 so that it will be better to use the ph 12 buffer in paper electrophoresis