Question: A method for separating polypeptides makes use of their differentail solubilities. The solubility of large polypeptides in water depends upon the relative polarity of their R groups, particularly the number of ionized groups: the more ionized groups there are, the more soluble the polypeptide. Which of each pair of polypeptides below is more soluble at the indicated pH?
a) (Gly)20 or (Glu)20 at pH 7
b) (Lys-Ala)3 or (Phe-Met)3 at ph 7.0
c) (Ala-Ser-Gly)5 or (Asn-Ser-His)5 at pH 6.0
d) (Ala-Asp-Gly)5 or (Asn-Ser-His)5 at pH 3.0