Problem 1
It has been hypothesized that early life-forms used only eight different amino acids to build small peptides. How many different 10-residue peptides could be constructed from eight amino acids?
Problem 2
If insulin (Fig. 5 − 1 ) were treated with mercaptoethanol to break its disulfide bonds, and then the mercaptoethanol were removed so that disulfide bonds could re-form, how many different ways could the two polypeptide chains become linked to each other (assuming that one or two disulfide bonds can form between the two chains)?
Problem 3
Which peptide has greater absorbance at 280 n m?#N#A. Gln-Leu-Glu-Phe-Thr-Leu-Asp-Gly-Tyr#N#B. Ser-Val-Trp-Asp-Phe-Gly-Tyr-Trp-Ala
Problem 4
Protein X has an absorptivity of 0.4 m L ⋅ m g − 1 ⋅ c m − 1 at 280 n m. What is the absorbance at 280 n m of a 2.0 m g ⋅ m L − 1 solution of protein X? (Assume the light path is 1 c m .)
Problem 5
You are using ammonium sulfate to purify protein Q ( p I = 5.0) by salting out from a solution at pH 7.0. How should you adjust the pH of the mixture to maximize the amount of protein Q that precipitates?
Problem 6
The blood of individuals with cryoglobulinemia contains proteins, mostly immunoglobulins, that, in contrast to most blood proteins, become less soluble at cold temperatures. Explain why a prominent symptom of cyroglobulinemia is damage to blood vessels and nearby cells in the skin.
Problem 8
Explain how you could use a column containing carboxymethyl groups to separate serum albumin and ribonuclease A (see Table 5 − 3 ).