1.Explain how you would isolate a mixture of Ala-Arg-Glu using a negatively charged resin (carboxylmethyl cellulose) and a positively charged resin (DEAE).

2.A sample of a peptide of unknown sequence was treated with trypsin; another sample of the same peptide was treated with chymotrypsin. The sequences (N-terminal to C-terminal) of the smaller peptides produced by trypsin digestion were

Met—Val—Ser—Thr—Lys

Val—Ile—Trp—Thr—Leu—Met—Ile

Leu—Phe—Asn—Glu—Ser—Arg

The sequences of the smaller peptides produced by chymotrypsin digestion were

Asn—Glu—Ser—Arg—Val—Ile—Trp

Thr—Leu—Met—Ile

Met—Val—Ser—Thr—Lys—Leu—Phe

Deduce the sequence of the original peptide.

3.Explain size exclusion chromatography.

4.Explain gel isoelectric gel electrophoresis. How does it relate to pI?