Free shipping on orders over $200
Free shipping on orders over $200
Molecular Weight
Purity
Storage
Appearance
Solubility
01
IGF-1 LR3 (Long Arg3 insulin-like growth factor-1) is an engineered analogue of human IGF-1, the growth factor that sits downstream of growth hormone in the GH axis. It is 83 residues long: the complete 70-residue IGF-1 sequence with one substitution (glutamic acid 3 replaced by arginine) plus a 13-residue extension at the N-terminus.
Both changes weaken binding to the IGF-binding proteins (IGFBPs) that normally sequester IGF-1, while preserving activation of the IGF-1 receptor. As a result, IGF-1 LR3 is widely used in cell culture and IGF-1 receptor research, where IGFBPs in serum or secreted by cells would otherwise blunt the response. It is supplied as a lyophilized reference material for in vitro research only.
02
IGF-1 LR3 keeps the folded core of IGF-1 and changes only the region that IGFBPs recognise.
N-terminal extension (residues 1–13)
The sequence MFPAMPLSSLFVN is added before the native IGF-1 chain. It lies near the IGFBP-binding surface and further reduces binding-protein affinity.
Arg3 substitution
In native IGF-1, Glu3 contributes to IGFBP binding. Replacing it with arginine (position 16 in the LR3 numbering) weakens that interaction.
Disulfide bonds
Like IGF-1, the molecule contains three intramolecular disulfide bonds that hold the folded structure together. Correct pairing is essential for activity.
Single chain
IGF-1 LR3 is a single, non-glycosylated polypeptide of about 9.1 kDa, typically produced recombinantly.
03
In vitro research focuses on IGF-1 receptor activation and on how reduced IGFBP binding changes the apparent potency of IGF-1.
IGF-1 receptor signalling
The IGF-1 receptor is a receptor tyrosine kinase. Binding triggers autophosphorylation and downstream PI3K/Akt and MAPK/ERK signalling, which are measured by phospho-specific immunoassays.
IGFBP interaction
Binding studies with purified IGFBPs compare IGF-1 LR3 with native IGF-1 and show the much weaker binding-protein affinity of the analogue.
Cell-based bioassays
Proliferation and protein-synthesis assays in responsive cell lines are used to characterise activity, often with native IGF-1 run in parallel.
All observations described here come from cell-free and cell-based in vitro systems.
04
Cell-culture supplement
Widely used in serum-free or low-serum media to support cell growth and productivity, where native IGF-1 would be bound by IGFBPs.
IGF-1 receptor studies
A standard agonist for activating the IGF-1 receptor in signalling experiments with less interference from binding proteins.
IGFBP research
Paired with native IGF-1 to study the role of binding proteins in controlling IGF availability.
Protein analytical methods
As a disulfide-bonded 9 kDa protein, it is a useful test case for reduced and non-reduced peptide mapping and intact-mass analysis.
05
Storage
Store the lyophilized powder at −20 °C, sealed and desiccated. Let the vial reach room temperature before opening.
Reconstitution
Dissolve first in a small volume of dilute acid, such as 10 mM HCl or 0.1 M acetic acid, then dilute into the working buffer. Swirl gently rather than vortexing.
Carrier protein
At low concentrations the protein can adsorb to plastic. Adding a carrier such as 0.1% BSA to working dilutions reduces losses.
Disulfide integrity
Avoid reducing agents (DTT, TCEP, β-mercaptoethanol), which break the disulfide bonds and inactivate the protein.
Solutions
Freeze single-use aliquots and avoid repeated freeze–thaw cycles. Use low-binding polypropylene tubes.
06
As a folded, disulfide-bonded protein, IGF-1 LR3 is characterised with protein-style methods as well as peptide methods.
HPLC
Reversed-phase HPLC (C4 or C8, wide-pore) separates the correctly folded form from misfolded, oxidised and truncated variants.
Intact mass
ESI-MS of the intact protein should match about 9111 Da. Reduction of the three disulfide bonds adds about 6 Da, which confirms they are present.
Disulfide mapping
Enzymatic digestion under non-reducing and reducing conditions, followed by LC-MS, confirms correct cysteine pairing.
SDS-PAGE
Shows a single band near 9 kDa and is a simple check for aggregates or fragments.
Biological activity
Because correct folding matters, lots are often also checked in a cell-based proliferation assay against a reference standard.
07
It has an arginine in place of glutamic acid at position 3 of the IGF-1 sequence and a 13-residue N-terminal extension, making it 83 residues instead of 70. Both changes reduce binding to IGF-binding proteins.
IGFBPs in serum or secreted by cells normally bind IGF-1 and limit how much reaches the receptor. With IGF-1 LR3, more of the added protein is available to activate the IGF-1 receptor.
Dissolve it in a small volume of dilute acid, such as 10 mM HCl or 0.1 M acetic acid, then dilute into the working buffer, ideally containing a carrier protein such as 0.1% BSA.
By intact mass, disulfide mapping under reducing and non-reducing conditions, reversed-phase HPLC, and often a cell-based activity assay against a reference standard.
No. It is supplied strictly as a reference compound for laboratory and analytical research and is not for human or animal use.
IGF-1 LR3 Research Reference. (2026). Pure Peptides Labs Research Catalogue. Retrieved from https://purepeptideslabs.net/research-catalogue/growth-hormone-axis-research-peptides/igf-1-lr3/
Materials listed on this platform are supported by independent testing and published documentation for laboratory research contexts.
