IGF-1 LR3 (Long R3 IGF-1) is an engineered analog of insulin-like growth factor-1. Two modifications — an arginine substitution at position 3 and an N-terminal extension — reduce its binding to IGF-binding proteins, giving it greater stability and availability in research systems. It is a widely used tool in cell-culture and growth-factor-signaling research.
What it is
As a modified growth-factor protein of roughly 83 residues, IGF-1 LR3 is larger and more structurally complex than the short peptides elsewhere in this library, complete with internal disulfide bonds. The same sequence-interpretation principles apply to reading its modifications, but its size means it is typically produced by recombinant expression rather than solid-phase synthesis.
Why researchers use it
Its reduced binding-protein affinity makes it a favored supplement in defined cell-culture media, where it delivers steady, reproducible receptor stimulation. Native IGF-1 is rapidly sequestered by binding proteins, but the LR3 analog remains available longer, which is convenient for experiments that need durable growth-factor input. Its proposed mechanism of action centers on the IGF-1 receptor and its downstream PI3K/Akt and MAPK pathways.
Relationship to the GH axis
IGF-1 is biologically downstream of growth hormone, so IGF-1 LR3 is often studied alongside growth-hormone-axis tools such as ipamorelin to connect upstream release signals with downstream growth-factor effects in model systems.
Preclinical footprint
Its use in proliferation, survival, and signaling assays is summarized in its preclinical research article, always framed as controlled-model work.
Research context
Protein identity and correct folding are critical, because a misfolded species can share the same mass yet behave differently — see HPLC vs. mass spectrometry and how to read a COA.
How to interpret the reagent
IGF-1 LR3 is best regarded as an intentionally deregulated laboratory analog, not as a direct stand-in for native IGF-1 biology. Its reduced interaction with binding proteins is useful for maintaining a stable experimental signal, but that same feature removes an important layer of physiological control. Results therefore answer questions about receptor signaling under the chosen culture conditions rather than reproducing the native ligand’s full regulatory environment. Comparisons with unmodified IGF-1, serum-free and serum-containing media, and receptor-blocking controls help define what the analog contributes. This distinction is fundamental to using the reagent without overextending conclusions beyond the model.
Product page: IGF-1 LR3 research vials.
Research Use Only. Supplied strictly for laboratory research and development — not for human or veterinary use, consumption, or any therapeutic or diagnostic purpose. This article is research education, not usage guidance.