IGF-1 LR3

Long R³ insulin-like growth factor-1

An 83-residue analogue of insulin-like growth factor-1, modified in two places so that it binds the IGF binding proteins far less readily than the native protein. It is a small protein rather than a short peptide, and it behaves like one — in the vial, in solution, and on a certificate.

Mechanism

Two modifications distinguish it from native IGF-1: an arginine in place of glutamic acid at position 3, and a 13-residue extension at the N-terminus. Both reduce affinity for the IGFBP family, which is the point — in serum-containing or serum-free culture, the binding proteins are what determine how much growth factor is actually free to signal.

Areas of research

• IGFBP binding and free-fraction studies
• Cell-culture supplementation and serum-free media development
• IGF-1 receptor signalling and downstream pathway work
• Protein-synthesis and tissue-model research

Identity and specification

It is not IGF-1, and the mass is the tell

Native human IGF-1 is 70 residues and around 7.6 kDa. This is 83 residues and 9117.5 Da. That is not a subtle difference and there is no reason for a laboratory to be unsure which one it has measured. A certificate for material sold as LR3 that reports a mass near 7.6 kDa is describing native IGF-1 — a different, and considerably cheaper, protein.

Two further things worth knowing before you compare our figure with somebody else’s:

• 9117.50 or 9117.60? Both are correct. The difference is which table of standard atomic weights the calculation used — the older values give 9117.50, the 2021 IUPAC values give 9117.60. We quote 9117.50 so that every molecular weight on this site is computed the same way. A supplier quoting the other figure is not wrong, and neither is a 0.1 discrepancy evidence of anything.
• Two CAS numbers are in circulation. You will see this compound registered as 143045-27-6 and as 946870-92-4, and reputable chemical suppliers list it under both. We quote the first and note the second rather than pick one and pretend the other does not exist. If you are cross-checking a certificate, match on the formula and mass, which are unambiguous, rather than on the registry number, which is not.
• The N-terminal extension is MFPAMPLSSLFVN. It is widely reprinted with the third and fourth residues transposed. The sequence above is the one that reproduces the published molecular formula when you build it residue by residue, which is the check that settles it.

Regulatory position — stated plainly

IGF-1 and its analogues are prohibited at all times in sport under the WADA List, and are treated as prescription-only medicines in a number of countries. This material is supplied for in-vitro laboratory research only: not for human or veterinary administration, not for diagnostic or therapeutic use, and we do not provide guidance on dosing or use. Card payment is not available for this compound — bank transfer or cryptocurrency only. If you are ordering from outside the UK, check that it may lawfully be imported where you are before you place the order; import rules for growth factors are stricter in many countries than for the short peptides we ship routinely.

Handling — a protein, not a peptide

The practical difference from the rest of our catalogue matters here. An 83-residue protein has real tertiary structure to lose, so it is less forgiving than a five-residue peptide: it denatures with agitation, with repeated freeze–thaw cycles, and at surfaces.

• Run the solvent down the vial wall, never onto the powder. Swirl, never shake — foaming is protein denaturing at the air–liquid interface, not cosmetic.
• Some laboratories reconstitute growth factors in dilute acetic acid rather than neutral water; see which solvent to use and our acetic acid water.
• Aliquot rather than repeatedly thawing one vial. Each cycle costs you material.
• Reconstituted material has a shorter useful window than a small peptide. Refrigerate and use promptly.

More on the general technique: how to reconstitute research peptides and reconstitution troubleshooting.

Sizes and pricing

Independently batch tested. A batch-specific certificate of analysis is available on request — ask for the certificate for the batch we would ship you before you order. Published certificates are in the COA library, each with the issuing laboratory’s verification key.

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