Native (non-denaturing) electrophoresis at pH 7.0 — Predict the migration directions of histones and myoglobin based on net charge

Introduction:
In native electrophoresis, proteins migrate according to their net charge and size at the working pH. This question tests understanding of isoelectric points and how pH relative to pI determines the direction of migration in an electric field.

Given Data / Assumptions:

• pH is 7.0 (near physiological).
• Histones are rich in Lys and Arg, giving high pI values (typically > 10).
• Myoglobin has a pI near neutral but is slightly below or around 7.0 depending on species; at pH 7.0 it is near neutral to slightly negative.
• Anode is the positive electrode; cathode is the negative electrode.

Concept / Approach:
Rule of thumb: if pH > pI, the protein carries net negative charge and migrates toward the anode. If pH < pI, the protein carries net positive charge and migrates toward the cathode. Compare pH 7.0 to each protein’s pI to determine direction.

Step-by-Step Solution:

Verification / Alternative check:
Running standards under native conditions commonly shows basic proteins moving toward the cathode, while acidic or slightly acidic proteins move to the anode. Minimal mobility occurs when pH equals pI exactly.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing electrode polarity; assuming myoglobin is neutral and immobile; overlooking that even small deviations from pI impart directionality, especially over longer runs.

Final Answer:
Histones migrate to the cathode; myoglobin migrates to the anode.