Question

the pk1, pk2, and pkr of the amino acid lysine are 2.2, 9.1, and 10.5, respectively. the pk1, pk2, and pkr of the amino acid arginine are 1.8, 9.0, and 12.5, respectively. a student at sdsu wants to use ion exchange chromatography to separate lysine from arginine. what ph is likely to work best for this separation?a) 1.5b) 2.5c) 5.5d) 7.5e) none of these

Answer 1

To separate lysine from arginine using ion exchange chromatography, a pH around 5.5 would work best.

Step-by-step explanation:

To separate lysine from arginine using ion exchange chromatography, the pH should be adjusted to a value where lysine and arginine have different charges. Lysine has a pKa1 of 2.2 and pKa2 of 9.1, while arginine has a pKa1 of 1.8 and pKa2 of 9.0. At low pH values below 2.2, lysine will be protonated and have a positive charge, while arginine will still be neutral. At high pH values above 9.1, both lysine and arginine will be deprotonated and have a negative charge. Therefore, a pH around 5.5 would work best for this separation, as lysine will be mostly charged while arginine will be mostly neutral.

Answer 2

To separate lysine from arginine using ion exchange chromatography, a pH higher than both of their pk1 values is needed. Option d) 7.5 is likely to work best for this separation.

Step-by-step explanation:

To separate lysine from arginine using ion exchange chromatography, we need to consider the ionization of the amino acids at different pH values. Lysine has a pk1 of 2.2, which means it starts to lose a proton and becomes negatively charged below pH 2.2. Arginine, on the other hand, has a pk1 of 1.8, so it starts losing a proton and becomes negatively charged below pH 1.8.

To separate lysine from arginine, we need a pH higher than both of their pk1 values. Therefore, option d) 7.5 would likely work best for this separation.