55. Two monomeric proteins migrate identically in SDS-polyacrylamide gel electrophoresis, but get separated in a gel-permeation chromatography experiment. This could be because:
A. They have different isoelectric points
B. One protein has more disulphide bonds
C. One protein is fibrous while the other is globular
D. One protein has more hydrophobic patches on its surface as compared to the other
Correct Answer: C. One protein is fibrous while the other is globular
Two monomeric proteins with identical SDS-PAGE migration (same molecular weight under denaturing conditions) separate in gel-permeation chromatography due to differences in native hydrodynamic volume caused by shape—one fibrous (elongated) elutes earlier than globular despite equal mass.
Option Analysis
A. They have different isoelectric points
Isoelectric point (pI) affects ion-exchange chromatography, not SDS-PAGE (denatures charge masking) or gel-permeation (size/shape only). Irrelevant for both techniques.
B. One protein has more disulphide bonds
Disulfide bonds affect native structure but SDS-PAGE fully denatures (reduces bonds), yielding identical migration. Gel-permeation uses native conditions, so doesn’t explain identical SDS-PAGE.
C. One protein is fibrous while the other is globular (Correct)
Fibrous proteins have larger hydrodynamic radius (elongated shape) despite same molecular weight, eluting earlier in gel-permeation. Globular proteins are compact, penetrate pores more, elute later. SDS-PAGE linearizes both equally.
D. One protein has more hydrophobic patches on its surface
Hydrophobicity affects reverse-phase HPLC or adsorption chromatography, not size-exclusion (no surface interactions) or SDS-PAGE (denatured).
One protein fibrous while other globular explains separation in gel-permeation chromatography despite identical SDS-PAGE migration—key biochemistry concept for GATE Life Sciences.
Shape-Based Separation
Gel-permeation separates by hydrodynamic radius: fibrous proteins (collagen-like) span larger effective volume, excluded from pores, elute first. Globular (myoglobin-like) compact, delayed elution.
Technique Comparison
| Technique | Denatured? | Separation Basis | Shape Effect? |
|---|---|---|---|
| SDS-PAGE | Yes | Mass only | None |
| Gel-permeation | No | Size/shape | Yes |
GATE Relevance
Tests native vs denatured protein behavior in biochemistry. Critical for understanding quaternary structure analysis and protein folding studies.
1 Comment
Vanshika Sharma
February 4, 2026One is fibrous and other is globular