If the pH is less than the pI in electrophoresis, what will the charge be?

When the pH of the environment is lower than the isoelectric point (pI) of a molecule, such as a protein, the overall charge of the molecule will be positive. This is because, at a pH below the pI, the amino groups of the amino acids are more likely to be protonated, giving the molecule a net positive charge.

The isoelectric point (pI) is defined as the pH at which a molecule carries no net charge. Therefore, if the pH is lower than the pI, it means there are more protons available in the solution, thus causing more acidic conditions. Consequently, the basic groups on the amino acids will remain positively charged while the acidic groups may not dissociate to form a negative charge to balance them out.

In the context of electrophoresis, where molecules migrate in an electric field based on their charge, a molecule with a positive charge will migrate towards the negative electrode, indicating that it is positively charged under acidic conditions (pH < pI).

So, the answer correctly identifying that the charge is positive when the pH is less than the pI reflects the principles of acid-base chemistry and protein behavior in different pH environments.