Chapter 6, Problem 6.37P

Interpretation Introduction

Interpretation:

To which terminal lysine will migrate in an isoelectric focusing experiment with gel of pH gradient $\text{1-12}$ is to be explained.

Concept introduction:

Isoelectric point (pI) or isoelectric pH is the pH at which the substance has a charge of zero. An amino acid’s pI is the average of two pKa values involving a zwitterions formation. Isoelectric focusing is a way used to separate amino acids or proteins using pH gradient.

If the pH of the solution is higher than the pI, the substance will deprotonate and will carry negative charge. Conversely, if the pH is lower than pI, the substance will protonate and will carry a positive charge. The substance remains uncharged if pI is equal to the pH and will not migrate to any electrode.

Any ion that has net positive charge (cations) will migrate toward the negatively charged terminal i.e. cathode and the ion with negative charge (anions) will migrate toward positively charged terminal i.e. anode.