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Long R3 IGF-1 vs IGF-1 LR3 — Same Peptide Explained
Research labs ordering peptides for the first time often waste hours verifying whether Long R3 IGF-1 and IGF-1 LR3 are different compounds. They're not. Both names refer to the same synthetic analog of insulin-like growth factor-1 (IGF-1), modified at the N-te
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- Research labs ordering peptides for the first time often waste hours verifying whether Long R3 IGF-1 and IGF-1 LR3 are different compounds. They're not. Both names refer to the same synthetic analog of insulin-like growth factor-1 (IGF-1), modified at the N-terminus with a 13-amino-acid extension and an arginine substitution at position 3. The confusion stems from inconsistent vendor nomenclature. Some suppliers list it as 'Long R3', others as 'LR3', and a few write out 'Long Arg3'. But the molecular structure, CAS number (946870-92-4), and biological function remain identical across all three naming conventions.
- Our team supplies research-grade peptides to biological research institutions, and we've clarified this naming ambiguity hundreds of times. The functional distinction that matters isn't the name. It's understanding why this analog exists in the first place and how its structural modifications differ from endogenous IGF-1.
- Is Long R3 IGF-1 the same compound as IGF-1 LR3?
- Yes. Long R3 IGF-1 and IGF-1 LR3 are identical peptides. Both names describe the same 83-amino-acid synthetic analog of human IGF-1, featuring a 13-residue N-terminal extension and an arginine substitution at position 3 (replacing glutamic acid). This modification reduces binding affinity to IGF binding proteins (IGFBPs) by approximately 100-fold compared to native IGF-1, extending the peptide's functional half-life in vitro from minutes to hours. Research applications rely on this extended bioavailability to study IGF-1 receptor signaling pathways without the rapid clearance seen with unmodified IGF-1.
- The naming convention split happened during early commercial synthesis in the 1990s. Academic publications typically used 'Long R3 IGF-1' to describe the structural modification (long N-terminal extension, arginine at position 3). Suppliers shortened this to 'LR3' for catalog listings, and both stuck. You'll see 'Long R3 IGF-1' in peer-reviewed studies published in journals like Endocrinology and The Journal of Biological Chemistry, while commercial peptide vendors. Including Real Peptides. Commonly use 'IGF-1 LR3' for product identification. The peptide synthesis protocol, purity standards, and amino acid sequencing remain identical regardless of which abbreviation appears on the vial label.