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BioTechnology QUESTION #10574
Question 1
Two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) separates proteins in two dimensions based on:
  • Size only (SDS-PAGE in both dimensions)
  • Isoelectric point (1st dimension) then molecular mass (2nd dimension)✔️
  • Hydrophobicity (1st dimension) then charge (2nd dimension)
  • Molecular mass (1st dimension) then isoelectric point (2nd dimension)
Correct Answer Explanation
2D-PAGE separates proteins by two independent properties:
  1. First dimension: Isoelectric focusing (IEF) on immobilised pH gradient (IPG) gels — proteins migrate to their pI where net charge = 0.
  2. Second dimension: SDS-PAGE — proteins are separated by molecular mass.
Individual protein spots are then identified by MALDI-TOF or ESI mass spectrometry after tryptic digestion, enabling full proteome characterisation.