IGF-1 LR3 — wholesale 10-vial kits

Research context

Native IGF-1 is tightly held by IGF-binding proteins (IGFBPs), which limit how much free growth factor reaches the IGF-1 receptor. IGF-1 LR3 was engineered to escape that control: the Glu3→Arg substitution and the N-terminal extension sharply reduce IGFBP binding, so the analog stays bioavailable in culture media and experimental systems far longer than native IGF-1.

Origin and molecular design. IGF-1 LR3 comes from a family of IGF-I fusion analogs expressed in E. coli by Francis and colleagues in Adelaide (Journal of Molecular Endocrinology, 1992). The 13-residue N-terminal extension is the first 11 residues of methionyl porcine growth hormone followed by Val-Asn, and position 3 of the IGF-I sequence carries Arg in place of Glu. The decisive evidence for the mechanism is comparative: in cell lines that secrete IGF-binding proteins into the medium, Long [Arg3]-IGF-I was the most potent analog of the series, whereas in chicken embryo fibroblasts, which secrete no detectable IGFBPs, it was less potent than native IGF-I. Its extra potency therefore comes from escaping IGFBP sequestration rather than from stronger receptor binding. The same authors noted that the hydrophobic extension helped the reduced, denatured fusion peptide refold into active material at high yield.

That property made IGF-1 LR3 a staple of cell-culture and bioprocess work, where it is used as a media supplement for mammalian cell lines. In signaling research it is a tool agonist for the IGF-1 receptor (IGF-1R): ligand binding to the receptor's α subunit triggers a conformational change in the β subunit that activates its tyrosine kinase, which phosphorylates IRS and Shc adaptors and drives the PI3K–Akt and Ras–MAPK pathways. In C2C12 myoblast culture it raises the differentiation index and nuclei count, and in the C26 tumour-bearing mouse model of cachexia it limited loss of muscle mass but accelerated tumour growth (Levolger et al., Scientific Reports, 2019) — a reminder that IGF-1R agonism is mitogenic in tumour models, which matters for experimental design and for handling. Infusion studies in guinea pigs reported that Long R3 IGF-I stimulated organ growth while lowering circulating IGF-I, IGF-II and IGFBP concentrations.

U.S. regulatory status: IGF-1 LR3 is not an FDA-approved drug. WholesalePeptide.us supplies it only for in-vitro, analytical and preclinical laboratory research. At 83 residues it is a protein under FDA's regulatory definition (an alpha amino acid polymer of more than 40 amino acids, 21 CFR 600.3) rather than a short synthetic peptide, so identity is confirmed by intact mass on the COA.

Unlike short synthetic peptides, IGF-1 LR3 contains three disulfide bonds that must form correctly for activity, so the COA's intact-mass result and the RP-HPLC profile together indicate whether the material is correctly folded and free of misfolded or truncated variants. Labs using it as a culture-media supplement usually titrate each new lot against the previous one, which is why lot-to-lot documentation matters.

It is supplied lyophilized as a single compound per kit.

Research areas

• IGF-1 receptor (IGF-1R) signaling
• PI3K–Akt and MAPK pathway studies
• Mammalian cell-culture media supplementation
• Muscle-cell differentiation (C2C12) and cachexia models
• Recombinant protein folding and disulfide-bond formation
• IGF-binding protein interaction studies

U.S. regulatory status of the compound (as an active ingredient): Not approved by the FDA. The material sold here is a research reference chemical, not a drug product.

Handling and storage

• Store lyophilized vials at −20 °C, sealed, protected from light and moisture.
• Let the vial reach room temperature before opening to limit condensation on the powder.
• Reconstitute in a dilute acidic buffer (for example 10 mM HCl or 0.1% acetic acid) per your lab's SOP, then dilute into assay buffer containing carrier protein.
• Aliquot reconstituted material and freeze once; avoid repeated freeze–thaw.