Question

The isoelectric point of histidine is \(7.64\). Toward which electrode does histidine migrate on paper electrophoresis at pH \(7.0\) ?

Short answer

Answer: Histidine will migrate towards the cathode (negative electrode) during paper electrophoresis at pH 7.0.

Step-by-step solution

Understand the concepts of isoelectric point and electrophoresis

Isoelectric point (pI) is the pH at which a molecule, in this case, histidine, carries no net electrical charge. Electrophoresis is a technique used to separate charged molecules like amino acids, based on their movement due to an electric field. In paper electrophoresis, an electric field is applied across a paper soaked in a buffer solution at a specific pH, and the amino acids migrate towards the electrode with an opposite charge.

Determine the charge of histidine at pH 7.0

To determine the charge of histidine at pH 7.0, compare the given pH with the isoelectric point (pI) of histidine: - If the pH < pI, then the molecule has a positive charge (protonated) and will migrate towards the negative (cathode) electrode. - If the pH > pI, then the molecule has a negative charge (deprotonated) and will migrate towards the positive (anode) electrode. In this case, the pH (7.0) is less than the isoelectric point (7.64) of histidine.

Determine the direction of migration based on the charge

Since the pH (7.0) is less than the isoelectric point (7.64), we can conclude that histidine will carry a positive charge at this pH. Therefore, it will migrate towards the negatively charged electrode (cathode) during paper electrophoresis.

Conclusion

Histidine will migrate towards the cathode (negative electrode) during paper electrophoresis at pH 7.0.