Which of the following amino acids gives Hopkins Cole colour reaction?
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Glycine
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Serine
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Tryptophan
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Histidine
C
Correct answer
Explanation
Hopkins-Cole reaction (also called glyoxylic acid test) is specific for tryptophan, which contains an indole ring that reacts with glyoxylic acid in presence of concentrated sulfuric acid to form a purple-colored product. Glycine, serine, and histidine do not contain indole rings and do not give this reaction.