第26至50題每題2.5分 26. Sam is trying to separate a protein mixture containing three proteins A, B, C. Protein A: homotetramer, Mr = 120,000, pI =6； Protein B: monomer, Mr = 80,000, pI=7； Protein C: monomer, Mr = 13,000, pI=9. Please choose the correct one from the following descriptions: (A) If Sam dissolves the mixture in 0.1 M Tris-HCl (pH 7) and uses SDS-PAGE to separate the mixture, the protein bands in the gel from top to bottom should be B-A-C. (B) If Sam dissolves the protein mixture in 20 mM phosphate buffer (pH 8) and loads it to an anion exchange column equilibrated with the same buffer, only protein C can bind to the column. (C) If Sam dissolves the mixture in 0.1 M Tris-HCl (pH 7) and uses size exclusion column to separate the mixture, protein C will be first eluted. (D) If Sam dissolves the mixture in 0.1 M Tris-HCl (pH 7) and uses size exclusion column to separate the mixture, the elution sequence is B-A-C. (E) If Sam dissolves the protein mixture in 20 mM phosphate buffer (pH 7) and loads it to a cation exchange column equilibrated with the same buffer, only protein A can bind to the column.