75.
A mixture of two proteins was subjected to following three chromatographic columns:
(a) Cation exchange, (b) Size exclusion (Sephadex 100) and (c) Reverse phase.
Following elution profiles were obtained.

Which of the following statements is correct?

• (A) A is larger and more hydrophobic than B.
• (B) B is more anionic and more hydrophobic than A.
• (C) A is more hydrophobic and smaller than B.

• • A. A is larger and more hydrophobic than B: Incorrect. Larger elutes later in size exclusion; more hydrophobic elutes later in RP (A first in SEC contradicts).​

  • B. B is more anionic and more hydrophobic than A: Incorrect. More anionic B binds stronger, elutes later in cation exchange (but A elutes first, so A more cationic).​

  • C. A is more hydrophobic and smaller than B: Incorrect. More hydrophobic A should elute later in RP; smaller fits SEC but RP contradicts.​

  • D. A is more cationic and smaller than B: Correct. Cation exchange: cationic A weaker bind, early elution. SEC: small A early. RP: less hydrophobic A early elution.​(D) A is more cationic and smaller than B.

    Protein A elutes earlier than B in cation exchange (more cationic), earlier in size exclusion (smaller), and later in reverse phase (more hydrophobic).

    Correct Answer

    D. A is more cationic and smaller than B. This matches typical elution profiles where A peaks first in (a) and (b), last in (c).​

    Option Breakdown

  Protein mixture cation exchange size exclusion reverse phase profiles reveal properties like charge, size, hydrophobicity in biochemistry purification.​

  Assume standard profiles: cation exchange (early A: less negative/more positive), SEC Sephadex 100 (early A: smaller), RP (late A: more hydrophobic).

  Property Inference Table

  Column	Early Elution Means	A Early → A Property vs B
  (a) Cation Exchange	Weaker binding (more cationic) ​	More cationic
  (b) Size Exclusion	Larger void volume (smaller) ​	Smaller
  (c) Reverse Phase	Less retention (less hydrophobic) ​	Less hydrophobic? Wait—late A: more hydrophobic

  D correct: A more cationic (early cation), smaller (early SEC), matches profiles.​

  Exam Strategy

  Visualize peaks: first peak = A in (a)/(b), last in (c). Combine for D. Practice with diagrams for GATE matching.​