IGF 1LR3

IGF-1 LR3 (Long R3 IGF-1, Long Arginine 3 IGF-1)

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> ⚠️ Research grade for in vitro cell culture and animal experiments only; not a drug; human injection is strictly prohibited; listed on WADA’s S2 Prohibited List

Basic Information

– CAS: 946870-92-4

– Aliases: LR3-IGF1, Igtropin, CL281, rhIGF-1 LR3 (recombinant)

– Amino acids: 83-peptide (natural IGF-1 is a 70-peptide)

– Two modifications:

1. A 13-amino acid extension chain added at the N-terminus: MFPAMPLLSLFVN

2. 3rd amino acid: Glu→Arg (E3R; origin of the name “R3”)

– Molecular weight: ~9117.5 Da

– Molecular formula: \(\boldsymbol{C_{406}H_{625}N_{111}O_{120}S_9}\)

– Appearance: White lyophilized powder

– Solubility: 0.1% acetic acid in AA water is recommended; sterile water may also be used; regular BAC water is not recommended (high pH may cause protein inactivation)

## Mechanism of Action

IGF‑1 LR3 is a long-acting recombinant IGF‑1 analog

1. Following modification, its affinity for IGFBP (IGF-binding protein) is significantly reduced, making it less likely to be captured and sequestered by IGFBP in vivo; thus, the proportion of free, active form is extremely high

2. Binds to the IGF-1R receptor, activating the PI3K/Akt/mTOR and MAPK/ERK signaling pathways

– mTOR: Enhances protein synthesis, inhibits protein degradation, and promotes cell hypertrophy

– ERK: Cell proliferation, satellite cell activation, and tissue repair

3. Potency is approximately 2–3 times that of native IGF-1

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> Native IGF-1 has a half-life of only 10–15 minutes; IGF-1 LR3 has a half-life of 20–30 hours

Research Applications

– Cell culture medium additive (for recombinant protein expression in CHO cells, etc.)

– Animal model studies on skeletal muscle cell proliferation and muscle hypertrophy

– Preclinical research related to cartilage, nerve, wound healing, and tissue regeneration

– Studies on the mechanisms of the GH/IGF-1 growth axis

Reconstitution & Storage (Important: IGF-1 LR3 is more sensitive than GHRH peptides)

1. Preferred solvent: 0.1% AA acetic acid water; do not use standard BAC sterile water

2. Example: 1 mg lyophilized vial + 1 mL 0.1% AA water → concentration 1 mg/mL

3. Lyophilized powder: Store at -20°C in a dry, light-protected environment; stability up to 2 years or more

4. After reconstitution: Aliquot into small portions and store at -20°C; avoid repeated freeze-thaw cycles; refrigerate at 2–8°C only for short-term use (1–2 weeks)

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> Repeated freeze-thaw cycles can easily lead to disulfide bond breakage, protein degradation, and a decrease in HPLC purity

Compliance Notice

1. For research laboratories, cell culture, and animal studies only; prohibited for human use