Lumera Labs Journal · Compendium
IGF-1 LR3: long-arginine-3 IGF-1 analog for muscle research
Published 2024-11-09 · Lumera Labs Editorial · Kelowna, BC
Short answer. IGF-1 LR3 is an 83-residue synthetic analog of insulin-like growth factor 1 with an N-terminal 13-residue extension and an Arg3 substitution that dramatically reduces binding to IGF-binding proteins. Investigated in published muscle-cell research. Available from $60 CAD.
What "LR3" means
"LR3" decomposes as: Long (the N-terminal 13-residue extension), R3 (an arginine substitution at position 3 replacing native glutamic acid). Together these modifications reduce binding to IGFBP-3 and IGFBP-5 by orders of magnitude relative to native IGF-1, increasing the free fraction available to IGF-1R in serum-containing assays.
Sequence and folding
Human IGF-1 has three internal disulfide bonds; the LR3 analog retains all three. Reference-grade IGF-1 LR3 must verify correct folding by reducing/non-reducing SDS-PAGE comparison, not just by HPLC purity. A high-purity sample with mis-folded disulfides will show normal HPLC retention but no receptor activity.
Quality criteria
- RP-HPLC purity ≥ 95% (folded proteins routinely cap below 99%).
- ESI-MS at 9117.4 Da (correctly folded form) ± 1.0 Da.
- Disulfide-pattern verification by reducing/non-reducing comparison.
- Endotoxin < 0.5 EU/mg.
In-vitro applications
C2C12 myoblast proliferation and differentiation assays, IGF-1R signaling readouts (Akt phosphorylation, S6K1), and serum-titration experiments where IGFBP-resistance matters. The LR3 form is preferred over native IGF-1 in serum-containing media because the IGFBP-resistance improves dose-response reproducibility.
Storage
Lyophilized at −20 °C, sealed under nitrogen. Reconstitute in slightly acidic bacteriostatic water (pH 4–5) at 1 mg/mL; folded IGF-1 LR3 has limited solubility at neutral pH. Stable 14 days at 2–8 °C in the acidified buffer; longer storage as −80 °C aliquots.
Lumera Labs ships HPLC-verified IGF-1 LR3 cold-chain across Canada from $60 CAD. View IGF-1 LR3 on the catalog →
Frequently asked questions
What does IGF-1 LR3 stand for?
Long-Arg3 IGF-1: an N-terminal 13-residue extension plus an arginine substitution at position 3 of native IGF-1.
Why is LR3 preferred over native IGF-1?
The Arg3 substitution and N-terminal extension reduce IGFBP binding by orders of magnitude, so the free fraction available to IGF-1R is much higher in serum-containing assays — improving dose-response reproducibility.
Is folding tracked on the COA?
It should be. A folded protein can have correct mass and HPLC purity but no activity if the disulfide pattern is wrong. Reference-grade material verifies folding by reducing/non-reducing SDS-PAGE comparison.
How is IGF-1 LR3 reconstituted?
Slightly acidic bacteriostatic water (pH 4–5) is preferred because folded IGF-1 LR3 has limited solubility at neutral pH.
Where to source IGF-1 LR3 in Canada?
Lumera Labs at /products/igf-1-lr3/ from $60 CAD; HPLC-verified, folding-confirmed, cold-chain shipped from Kelowna.
Disclaimer: All Lumera Labs products are supplied for laboratory research use only. They are not approved by Health Canada for human consumption, therapy, or diagnosis. See our research-use declaration for full terms.