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IGF-1 LR3

IGF-1 LR3 (Insulin-like Growth Factor-1 Long R3, CAS 67763-96-6) is an 83-amino acid recombinant analog of human IGF-1 with a molecular weight of approximately 7,649 Da and formula C₃₃₁H₅₁₂N₉₄O₁₀₁S₇. The LR3 designation refers to a Glu³→Arg substitution and a 13-amino acid N-terminal extension peptide, modifications that dramatically reduce IGF binding protein (IGFBP) affinity while preserving IGF-1 receptor (IGF-1R) potency. This engineered IGF-1 variant is a key research tool for studying receptor-mediated anabolic signaling independent of IGFBP sequestration.

Technical Specifications

Property Value
CAS Number 67763-96-6
Molecular Formula C₃₃₁H₅₁₂N₉₄O₁₀₁S₇
Molecular Weight ~7,649 Da
Purity ≥99% (HPLC-verified)
Appearance Lyophilized white powder
Solubility Soluble in dilute acetic acid or aqueous buffers
Storage -20°C (lyophilized), 2–8°C (reconstituted)

Mechanism of Action

IGF-1 LR3 binds to the type 1 insulin-like growth factor receptor (IGF-1R), a heterotetrameric (α₂β₂) receptor tyrosine kinase, with a binding affinity comparable to native IGF-1. Receptor activation triggers autophosphorylation of tyrosine residues in the β-subunit kinase domain, recruiting IRS-1 adaptor proteins and activating two major downstream pathways: PI3K/Akt/mTOR, which drives protein synthesis, glucose uptake, and cell survival; and Ras/Raf/MEK/ERK, which promotes cell proliferation and differentiation. The critical advantage of the LR3 modification lies in its 100- to 1,000-fold reduced affinity for IGFBPs (particularly IGFBP-3, which normally sequesters >99% of circulating IGF-1). By evading IGFBP binding, IGF-1 LR3 achieves dramatically increased bioavailability and a prolonged half-life in culture and in vivo, allowing sustained IGF-1R engagement. Additionally, IGF-1 LR3 retains moderate cross-reactivity with the insulin receptor (IR), particularly the IR-A isoform, contributing to its metabolic effects on glucose transport.

Research Applications

  • Primary: IGF-1 receptor signaling — PI3K/Akt/mTOR pathway, protein synthesis, muscle hypertrophy
  • Secondary: Cell proliferation and differentiation, glucose transport and metabolism, IGFBP biology (comparative studies with native IGF-1)
  • Model Systems: In vitro (L6 myoblasts, C2C12 myotubes, 3T3-L1 adipocytes), in vivo (growth and body composition models, muscle regeneration studies)

Quality Control & Analytical Methods

  • HPLC: ≥99% purity verification at 214/220 nm (C18 reversed-phase column)
  • Mass Spectrometry: ESI-MS for molecular weight confirmation (~7,649 Da)
  • Peptide Content: Amino acid analysis (AAA) for net peptide content determination
  • Endotoxin: <1 EU/mg (LAL assay)
  • TFA Content: <1% (ion chromatography)

Stability & Storage

Condition Stability
-20°C (lyophilized) 24 months
4°C (lyophilized) 6 months
25°C (lyophilized) 1 month
Reconstituted (4°C) 7 days
Reconstituted (-20°C) 30 days

Key Research References

  • Tomas et al. (1998) — Long R3 IGF-I: a variant with enhanced anabolic potency due to reduced IGFBP binding. Biochem J. PMID: 9445384
  • Clemmons (2007) — Modifying IGF1 activity: an approach to improve anabolic outcomes. J Mol Endocrinol. PMID: 17183215
  • Adams (2002) — Autocrine and/or paracrine insulin-like growth factor-I activity in skeletal muscle. J Appl Physiol. PMID: 12235021

Source & Purchase

For researchers requiring research-grade IGF 1 with full analytical documentation including HPLC, LC-MS, and Certificate of Analysis, visit the HK Peptides product page for specifications, bulk pricing, and ordering.

View IGF 1 Product →

FAQ

Q: What purity level is standard for IGF-1 LR3? A: HK Peptides supplies IGF-1 LR3 at ≥99% purity by HPLC with full COA documentation.

Q: How should IGF-1 LR3 be stored for research use? A: Lyophilized IGF-1 LR3 should be stored at -20°C. Reconstituted solutions at 4°C for short-term use (up to 7 days). Avoid repeated freeze-thaw cycles.