Mixtures of amino acids can be analyzed by separating the mixture into its compo
ID: 575484 • Letter: M
Question
Mixtures of amino acids can be analyzed by separating the mixture into its components through ion- exchange chromatography. Amino acids placed on a cation-exchange resin containing sulfonate (-SO3) groups flow down the column at different rates because of two factors that influence their movement: (1) ionic attraction between the sulfonate groups on the column and positively charged functional groups on the amino acids, and (2) hydrophobic interactions between amino acid side chains and the strongly hydrophobic backbone of the polystyrene resin. For each pair of amino acids listed, determine the order of elution from a cation exchanger in pH 7.0 buffer. Amino Acid Pair | utes First Elutes Second Glu and Arg Lys and Met Gly and Asp Ala and Leu Phe and Ser Gly AlaLeu SerPhe Arg Me Lys Asp GluExplanation / Answer
The more the pI of amino acid from the given pH more the positive charge on it and hence more the tendancy to elute first.
a) Between Glu and Arg, The pI of glu is 3.22 so will have net negative charge, pI of Arg is 10.76 so net charge will be positive, hence Arg will elute first and Glu second
b) Between Lys and Met .The pI of Lys is 9.74 so net positive charge, the pI of Met 5.74 , so net negative charge, Hence Lys will elute first and Met second
c) Between Gly and Asp , the pI of Gly is 5.97 so will have a net negative charge and Asp has pI of 2.77 so it will also be net negatively charged, however Gly will elute first and Asp second
d) Between Ala and Leu the pI of Ala is 2.77 so net negative charge, while of Leu is 5.98. So Leu will elute first and Ala second.
e) Between Phe and Ser, the pI of Phe is 5.91 and pI of Ser is 5.68. so Phe will elute first.