What is aminoisobutyric acid?
Aminoisobutyric acid (Aib) is a non-standard amino acid with two methyl groups on the alpha-carbon instead of the methyl-and-hydrogen pattern of standard amino acids. Used in synthetic peptide engineering to block dipeptidyl peptidase IV (DPP-IV) cleavage at the N-terminal end of the peptide.
What the research literature says
Aib is structurally distinctive because it lacks the chirality of standard amino acids (the alpha-carbon has two identical methyl groups, making it achiral) and because the dimethyl substitution constrains backbone conformation. The constrained backbone geometry plus the steric bulk of the two methyl groups blocks proteolytic-enzyme recognition at the modified position, providing localised protease resistance.
For semaglutide specifically, Aib substitution at position 8 blocks the canonical DPP-IV cleavage site that would otherwise rapidly degrade native GLP-1 in circulation. The combination of the Aib substitution plus the C18 fatty-acid sidechain for albumin binding produces the ~7-day plasma half-life characterising semaglutide’s once-weekly dosing profile (PMID 27633186 Marso cardiovascular outcomes; PMID 33567185 Wilding STEP-1).
Aib is also used in ipamorelin (at the N-terminal position, again blocking DPP-IV cleavage) and in other GLP-1 analogues with similar engineering strategies. The non-standard-amino-acid framework is a standard tool in long-acting peptide pharmaceutical engineering.
Why this matters in research context
Aib matters in peptide-research contexts as one of the engineering modifications that distinguishes long-acting peptide pharmaceuticals from native peptide hormones. Researchers reading peptide sequences should recognise “Aib” or non-standard amino-acid abbreviations as engineering-modification markers that signal a synthetic compound with altered pharmacokinetic properties relative to the unmodified native analogue.
Related compounds
- Semaglutide 10mg — Aib substitution at position 8
- Ipamorelin 10mg — Aib at the N-terminal position
Related research questions
References
- Marso SP et al. Semaglutide and Cardiovascular Outcomes in Patients with Type 2 Diabetes. N Engl J Med 2016;375(19):1834-1844. [PMID 27633186]
- Wilding JPH et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity. N Engl J Med 2021;384(11):989-1002. [PMID 33567185]
- Raun K et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol 1998;139(5):552-561. [PMID 9849822]
Research-questions pages describe research-context use of peptide-research terminology. They do not constitute medical, veterinary, or clinical advice. Every compound in the Ronin catalog is sold strictly for laboratory and research use only.