IGF-1 LR3, short for Long Arg3 Insulin-like Growth Factor-1, is best known in the lab as a cell-culture reagent. Biotechnology groups have used it for decades as a serum-free media supplement, and cell biologists use it as a tool compound for studying IGF-1 receptor (IGF-1R) signaling. This overview explains what makes the analog structurally different from native IGF-1 and what to check when sourcing it.
What Is IGF-1 LR3?
Native IGF-1 is a 70-amino-acid protein hormone. IGF-1 LR3 is an 83-amino-acid analog with two changes: a 13-residue N-terminal extension peptide and substitution of glutamic acid with arginine at position 3. Together these modifications sharply reduce binding to IGF-binding proteins (IGFBPs), which in cell culture otherwise sequester native IGF-1 and blunt its availability to receptors.
Because of its size, IGF-1 LR3 is typically produced recombinantly rather than by short-chain solid-phase synthesis, and it contains three disulfide bonds that must form correctly for proper folding.
Why Reduced IGFBP Binding Matters
Cultured cells secrete IGFBPs into the media. With native IGF-1, those binding proteins capture much of the ligand, making dose-response curves harder to interpret. IGF-1 LR3's low IGFBP affinity means that more of the added ligand remains free to interact with IGF-1R, which is why published bioprocessing work describes it as more potent than native IGF-1 in culture. For researchers, it offers a cleaner way to probe receptor signaling without the IGFBP variable.
Common Laboratory Research Themes
- Serum-free media formulation: supporting cell proliferation in bioprocessing and cell-line work.
- IGF-1R signaling: PI3K/Akt and MAPK/ERK pathway activation assays.
- IGFBP studies: comparing native IGF-1 and LR3 to quantify binding-protein effects.
- Receptor cross-talk: examining IGF-1R versus insulin receptor activation in cell models.
These are in-vitro and preclinical research themes only and are not a basis for any claim about effects in people.
IGF-1 LR3 Specifications at a Glance
- Class: IGF-1 analog
- Length: 83 amino acids
- Key changes: Arg3 substitution, 13-residue N-terminal extension
- Form: lyophilized powder
- Size: 1mg vial
- Verification: HPLC purity and MS identity, third-party tested
Quality Documentation
For a larger protein like IGF-1 LR3, mass spectrometry should confirm the full 83-residue mass (roughly 9.1 kDa), and HPLC purity should be reported as a chromatographic area percentage. Our guides on net peptide content vs purity percentage and endotoxin testing are especially relevant for cell-culture use, where endotoxin can confound results. Genetic Peptides USA lots are PepAssure third-party verified with lot-specific COAs.
Storage and Stability
Proteins with disulfide bonds are sensitive to repeated freeze-thaw cycles and aggregation. Lyophilized material is best stored cold and dry; many labs aliquot solutions to avoid repeated cycling. See how lyophilization works for background.
Where to Go Next
Review lot details on the IGF-1 LR3 1mg research peptide page or browse all research peptides. Related guides: Tesamorelin overview and GMP vs research-grade peptides.
Frequently Asked Questions
What does LR3 stand for?
Long Arg3: the analog carries a 13-residue N-terminal extension (Long) and an arginine substitution at position 3 (R3).
How long is IGF-1 LR3?
It is an 83-amino-acid analog of the 70-amino-acid native IGF-1, with three disulfide bonds.
Why is IGF-1 LR3 used in cell culture?
Its low affinity for IGF-binding proteins keeps more ligand available to the IGF-1 receptor in culture media than native IGF-1.
What should an IGF-1 LR3 COA show?
Lot number, HPLC purity as an area percentage, and a mass spectrometry result consistent with the full 83-residue sequence.
Is IGF-1 LR3 for human or animal use?
No. It is sold for laboratory research use only, not for human or veterinary use, and is not intended to diagnose, treat, cure, or prevent any disease.
All products referenced in this article are sold strictly for laboratory research use only. They are not for human or veterinary use, are not drugs, foods, or cosmetics, and are not intended to diagnose, treat, cure, or prevent any disease. Nothing here is guidance on administration or handling outside a qualified laboratory setting.