At pH 8.6 in serum protein electrophoresis, what is true about the proteins?

At pH 8.6 in serum protein electrophoresis, what is true about the proteins?

• A. Exhibit net negative charge
• B. Exhibit net positive charge
• C. Exhibit charge neutrality
• D. They migrate toward the cathode

Answer: (A)

Proteins carry charge that depends on the pH relative to their isoelectric point. When the pH is above a protein’s isoelectric point, it has a net negative charge; below it, a net positive charge; at the isoelectric point, it is charge-neutral. At pH 8.6, most serum proteins have a pI around 4–6, so the pH is well above their pI, giving them a net negative charge. In electrophoresis, negatively charged proteins migrate toward the positive electrode (the anode), not the cathode. Thus, the true statement is that they exhibit net negative charge.

Proteins carry charge that depends on the pH relative to their isoelectric point. When the pH is above a protein’s isoelectric point, it has a net negative charge; below it, a net positive charge; at the isoelectric point, it is charge-neutral. At pH 8.6, most serum proteins have a pI around 4–6, so the pH is well above their pI, giving them a net negative charge. In electrophoresis, negatively charged proteins migrate toward the positive electrode (the anode), not the cathode. Thus, the true statement is that they exhibit net negative charge.