IGF-1 LR3
Long-Arg3 IGF-1 (long-acting IGF-1 analog)
Overview
IGF-1 LR3 (Long R3 IGF-1) is an engineered 83-amino-acid analog of native IGF-1 with two structural modifications: a 13-amino-acid N-terminal extension and an Arg substitution at position 3 (in place of native Glu3). The N-terminal extension came originally from a serendipitous E. coli fusion-protein construct and was found to dramatically reduce binding affinity for the IGF-binding-protein family (IGFBPs), while the Arg3 substitution further suppresses IGFBP interaction. Both modifications together produce a circulating analog that is largely free of IGFBP sequestration, the practical consequence is roughly 3-fold higher biological potency in cell-proliferation assays compared with native IGF-1 at equivalent molar concentrations, plus an extended functional half-life because the molecule is not removed from circulation by IGFBP-mediated clearance. Lyochem supplies recombinant IGF-1 LR3 as a lyophilized powder at ≥99.0% HPLC purity. As a recombinant protein expressed in E. coli, the release packet emphasizes both chemical purity (RP-HPLC) and biological activity verification, the latter typically by SDS-PAGE for size, plus optional cell-proliferation bioassay (3T3 or MCF-7 cells) for activity confirmation. Endotoxin (LAL) is included by default for IGF-1 LR3 because the recombinant-protein process can carry over higher endotoxin loads than synthetic peptides. Three standard fill sizes (100 mcg, 1 mg, 2 mg) cover cell-culture aliquot scales through in vivo research workflows.
Who buys this, and why
GH-axis peptides ship to research labs studying somatotropic-pathway pharmacology, IGF-axis signalling, and pulse vs. sustained-elevation GH biology. Buyers qualifying a new source typically request sequence verification on the first lot, the counter-ion form (acetate by default), and stability data at −20 °C. Blends — the CJC-1295 + Ipamorelin co-formulated lot is the canonical example — are co-lyophilised rather than solution-mixed so the ratio is locked at the lyophilisation step.
Primary buyer fit: academic and contract research laboratories.
Specifications
- CAS
- 946870-92-4
- Purity (HPLC)
- ≥ 99.0%
- Common vial sizes
- 100 mcg, 1 mg, 2 mg
- MOQ
- On request
- Lead time
- 14–21 days
- Storage
- -20°C, protect from light
Documentation available on request
- Lot-specific Certificate of Analysis (CoA)
- RP-HPLC chromatogram with peak integration
- ESI-MS identity confirmation (±0.5 Da)
- Sequence verification by LC-MS/MS
- Water content by Karl Fischer
- SDS / MSDS
- Counter-ion analysis (acetate vs TFA)
- Stability at −20 °C across 12 months
- Solubility in BAC water / PBS reconstitution
Regulatory note
Sold for Research Use Only under the receiving laboratory's institutional and jurisdictional regulations. Not a finished dosage form, not labelled for human administration, and not supplied to compounding pharmacies — Lyochem's GH-axis lots are scoped to research workflows only. Buyers studying somatotropic pharmacology should specify the counter-ion form (acetate by default) and any pulse-vs-sustained study design notes at quote stage.
Frequently asked questions
Why is IGF-1 LR3 used in research instead of native IGF-1?▾
Native IGF-1 is heavily sequestered by IGFBPs in serum and cell-culture environments, typically less than 1% of total IGF-1 is free at any given time. This makes dose-response work and concentration-controlled experiments difficult because the effective free concentration is hard to predict. IGF-1 LR3's two engineered modifications (N-terminal extension and Arg3 substitution) dramatically reduce IGFBP binding, producing a more linear and predictable dose-response. The practical readout in cell-proliferation assays is roughly 3-fold higher potency than native IGF-1 at equivalent molar concentrations, with substantially less inter-experiment variability.
Is IGF-1 LR3 a peptide or a recombinant protein, and what does that mean for analytics?▾
At 83 amino acids, IGF-1 LR3 is at the boundary between large peptide and small protein, practically, it's produced by recombinant expression in E. coli rather than solid-phase synthesis. The analytical packet therefore differs from typical synthetic peptides: RP-HPLC for chemical purity, SDS-PAGE for size confirmation, mass spec (sometimes intact-mass or peptide-mapping), plus a bioactivity readout (cell-proliferation assay) is recommended because recombinant material's biological activity can vary with folding even when chemical purity is high. Endotoxin (LAL) is essential for IGF-1 LR3 because the E. coli expression system requires careful endotoxin clearance during purification.
How should IGF-1 LR3 be reconstituted and stored?▾
Lyophilized IGF-1 LR3 reconstitutes in 0.6% acetic acid (rather than plain water), the slight acidification keeps the protein in monomer form and avoids aggregation that can occur at neutral pH on dilute reconstitution. After reconstitution, dilute working stocks should be prepared in cell-culture-grade BSA-containing buffer (typically 0.1% BSA) to prevent adsorption to glass and plastic surfaces at low working concentrations, this is critical for cell-culture work at sub-100 ng/mL. Working stocks should be aliquoted into single-use volumes and held at -20 °C; lyophilized product follows the standard 24-month re-test window.
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