Fall2018 BIOL203 Homework 1 1. You discover a small protein containing only 10 a

Question

Fall2018 BIOL203 Homework 1 1. You discover a small protein containing only 10 amino acids, called interleukin-87 (IL-87), that is involved in modulating the immune response. You are interested in urifying this small peptide so that you can study its function further. The following nalyses (A-E) were performed on the purified peptide to determine its sequence and structure. A. Upon reaction with fluro-4.4-dinitropheno! (FDNB or Sanger reagent), you obtain DNP.Arg and DNP-Asp, leading you to believe your protein may not be pure after all. B. You then perform isoelectric focusing on IL-87 and observe only one band, as expected, at pH 6.25. IL-87 is then treated with dithiothreitol (DTT) and the protein is again subject to isoelectric focusing. Much to your relief, you obtain two bands, one at pH of 10 and one at pH of 2.85. Explain what you know so far about the protein (after steps A and B) and why you are relieved.

Explanation / Answer

We can know till now that this particular peptide has contain arginine amino acid and aspartic acid as in N terminal.

This is so because FDNB react with amino group of amino acid present at N terminal. Hence, we can say these two amino acid are present at N terminal.

Second information we got is that since argininge is basic in nature and aspartic acid is acidic in nature. We got two bands.

We are finally relieved because, we are getting two bands. One band correspond to ph of 10 because of the presence of arginie amino acid at N terminal and other pH is 2.85 because of presence of aspartic acid. Hence, we are getting protein in purified form.

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