05:19
Principles of Biochemistry
Mixtures of amino acids can be analyzed by first separating the mixture into its components through ionexchange chromatography. Amino acids placed on a cation-exchange resin (see Fig. $3-17$ a) containing sulfonate $\left(-\mathbf{S O}_{3}^{-}\right)$ groups flow down the column at different rates because of two factors that influence their movement: (1) ionic attraction between the sulfonate residues on the column and positively charged functional groups on the amino acids, and
(2) aggregation of nonpolar amino acid side chains with the hydrophobic backbone of the polystyrene resin. For each pair of amino acids listed, determine which will be eluted first from the cation-exchange column by a pH 7.0 buffer.
(a) Aspartate and lysine
(b) Arginine and methionine
(c) Glutamate and valine
(d) Glycine and leucine
(e) Serine and alanine