IGF1-LR3 — Long R3 insulin-like growth factor 1 — is a recombinant analogue of human IGF-1 carrying two deliberate modifications.
The two changes and why they exist
First, the glutamic acid at position 3 is replaced with arginine. Second, a 13-amino-acid extension is added at the N-terminus. Together these dramatically reduce the molecule’s affinity for IGF binding proteins.
That reduction is the entire point. In normal physiology the large majority of circulating IGF-1 is bound to IGFBPs, which act as a reservoir and brake — sequestered IGF-1 cannot engage its receptor. By evading that system, IGF1-LR3 remains free and available, which is why it shows substantially greater potency than native IGF-1 in cell culture at equivalent concentrations.
Target
It acts at the IGF-1 receptor, a receptor tyrosine kinase, activating the PI3K/Akt and MAPK/ERK cascades associated with cell growth, protein synthesis and inhibition of apoptosis.
Implications for experimental design
The binding protein system exists for a reason, and removing it changes how the molecule behaves in an assay. Because IGF1-LR3 remains free rather than sequestered, effective concentrations are far lower than native IGF-1 and dose–response curves are shifted accordingly. Protocols written for native IGF-1 will overshoot.
The PI3K/Akt axis it activates is proliferative and one of the most intensively studied pathways in cell biology. In practice that means cell line selection and passage control matter: transformed lines already carry alterations in this pathway, and growth responses can be difficult to attribute cleanly. Native IGF-1 or a binding-protein-competent control is usually the appropriate comparator.
Supplied lyophilised. See our reconstitution protocol for handling technique and diluent selection.
Every batch ships with a third-party certificate of analysis. View IGF1-LR3 and its current COA.
Research use only
Isla Longevity supplies this compound for laboratory research use only. It is not approved by the FDA for human or veterinary use and is not for human consumption. This article summarises published research and is not medical guidance.
