1. Tardigrade
  2. Question
  3. Chemistry
  4. A tetrapeptide has -COOH group on alanine. This produces glycine (Gly), valine (Val), phenyl alanine (Phe) and alanine (Ala), on complete hydrolysis. For this tetrapeptide, the number of possible sequences (primary structures) with -NH2 group attached to a chiral center is

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Q. A tetrapeptide has $-COOH$ group on alanine. This produces glycine (Gly), valine (Val), phenyl alanine (Phe) and alanine (Ala), on complete hydrolysis. For this tetrapeptide, the number of possible sequences (primary structures) with $-NH_{2}$ group attached to a chiral center is

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Solution:

Solution
Solution
Solution
Solution
No. of possible sequences (primary structures) with $-\text{N}\text{H}_{2}$ group attached to a chiral center is 4.
Since $\text{-COOH}$ group is attached to alanine, one terminal of the tetrapeptide contains alanine. Thus, its position is fixed.
Glycine is achiral whereas valine and phenylalanine are chiral. Thus, $\text{-NH}_{\text{2}}$
group is attached to either valine or phenylalanine.
Thus following are the four possible combinations of the tetrapeptide.
$H_{2}​N-Val-Gly-Phe-Ala-COOH$
$H_{2}​N-Val-Phe-Gly-Ala-COOH$
$H_{2}​N-Phe-Gly-Val-Ala-COOH$
$H_{2}​N-Phe-Val-Gly-Ala-COOH$