Question

15. Which is used to reduce the disulfide bonds in proteins? D) iodoacetate B) performic acid C) DTT A) PITC 16. What is the net charge on the tripeptide Gly-Asp-Lys at pH 1.5? The table below gives the pKa's of the ionizable groups on the free amino acids. Free amino acid pK, of a-Carboxyl pKs of side chain pKa of a-amino group 2.4 group 9.8 Glycine Aspartate Lysine 2.0 3.9 9.9 2.2 9.1 10.5 A) -2 B) C) D) +2 +1 17. A mixture of four proteins (A, B, C and D) is applied to a cation exchange column at low pH. The pH of the buffer applied to the column is gradually increased. Given the information supplied, which will elute last? Protein Molecular Weight (g/mol) 35,000 26,000 146,000 26,000 pl 3.4 8.0 7 4.7 W 9.1 B) y and w elute nearly together A) x D) W C) z

Answer 1

15) DTT can be used to reduce disulphide bonds. These reducing agents work same as GSH, except that DTT, because it has two thiol groups. when the molecule gets oxidized,the dithiol group unites to form disulfide bridge in DTT.