A-LevelChemistryCarboxylic acids and derivativesOct/Nov 2018Paper 4 Q95 Marks
(a) Use information from the Data Booklet to draw the structure of the dipeptide glu-cys. The isoelectric point is the pH at which an amino acid exists as a zwitterion. The isoelectric point of glutamic acid is 3.2 and of cysteine is 5.0. A mixture of the dipeptide glu-cys and its two constituent amino acids, glutamic acid and cysteine, was analysed by electrophoresis using a buffer at pH 5.2. The results obtained are shown. [Figure 9.0]
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