Detailed Explanation
Any amino acid not among the 20 standard proteinogenic amino acids encoded by the genetic code. Hundreds of unnatural amino acids (UAAs) are used in peptide drug design to improve metabolic stability, enhance receptor selectivity, increase cell permeability, or add chemical functionalities not available from natural building blocks.
Common examples include D-amino acids (mirror images of natural L-forms, conferring protease resistance), α-aminoisobutyric acid (Aib, helix-promoting), norleucine (Met isostere without oxidation liability), β-amino acids (extra backbone carbon, protease resistant), and photo-crosslinking amino acids (for studying protein interactions). Semaglutide contains Aib at position 8, which is an unnatural amino acid that confers DPP-IV resistance.
Key Facts
- Any amino acid not among the 20 standard proteinogenic amino acids encoded by the genetic code.
- Hundreds of unnatural amino acids (UAAs) are used in peptide drug design to improve metabolic stability, enhance receptor selectivity, increase cell permeability, or add chemical functionalities not available from natural building blocks.
- Common examples include D-amino acids (mirror images of natural L-forms, conferring protease resistance), α-aminoisobutyric acid (Aib, helix-promoting), norleucine (Met isostere without oxidation liability), β-amino acids (extra backbone carbon, protease resistant), and photo-crosslinking amino acids (for studying protein interactions).
- Semaglutide contains Aib at position 8, which is an unnatural amino acid that confers DPP-IV resistance.
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