IGF-1 LR3

The difference is 13 extra residues on the N-terminus and one point substitution, Arg for Glu at position 3, giving 83 residues instead of 70 and around 9112 g/mol instead of roughly 7649. Functionally the difference that matters is binding protein affinity: both modifications fall in the region IGF binding proteins recognise, so IGF-1 LR3 binds IGFBP-3 far more weakly than native IGF-I while retaining high affinity at the type 1 IGF receptor. Any experiment run in medium containing serum or secreted IGFBPs will therefore behave differently with the two molecules, and molar calculations must state which one the mass refers to.

Yes, IGF 1 LR3, IGF-1 LR3, Long R3 IGF-1, Long-[Arg3]-IGF-I and LR3IGF-I all refer to the same 83 residue analogue. The unhyphenated IGF 1 LR3 spelling is simply a common search variant. The literature usually writes it Long-[Arg3]-IGF-I, and biopharmaceutical suppliers market it under the trade style LONG R3 IGF-I as a cell culture supplement. Quoting CAS 946870-92-4 avoids ambiguity when sourcing reference material.

Because both of its modifications sit in the part of the molecule that IGF binding proteins read. The N-terminal tripeptide region of IGF-I contributes directly to IGFBP contact, so extending the N-terminus by 13 hydrophobic residues and swapping the acidic Glu3 for basic Arg3 disrupts that interface while leaving the receptor-binding surface intact. Ballard and colleagues (Growth Regulation, 1993) put the affinity gap at roughly one thousand fold for IGFBP-3. Wilson and colleagues later reported that, unlike IGF-I, the Long R3 variant did not raise serum IGFBP-3 in adolescent monkeys, consistent with the same structural argument.

There is no published human pharmacokinetic half-life for IGF-1 LR3, because the compound has never been through a human trial. The multi-day and twenty-plus-hour figures circulated online are not traceable to any peer-reviewed human dataset and should be treated as unsourced. What the literature does support is a mechanistic argument rather than a number: because the analogue largely escapes IGFBP binding, its distribution and clearance in animal models differ from native IGF-I, and Ballard and colleagues examined exactly that comparison in 1993. Any half-life value used in a research design should come from the model system being used.

No. Published IGF-1 LR3 research is entirely preclinical, covering cell culture plus rat, pig and non-human primate models, including work on intestinal growth in rodents and on hypoglycaemic potency in pigs and marmosets. It is not an approved medicine in any jurisdiction and holds no marketing authorisation. It is also prohibited in sport, since the WADA Prohibited List covers insulin-like growth factor 1 and its analogues under section S2. Supplied strictly for laboratory research use, not for human or veterinary use.

Its most established use is as a growth factor supplement in serum-free mammalian cell culture, where Morris and Schmid (Biotechnology Progress, 2000) compared LongR3 against insulin in CHO lines expressing recombinant proteins, and where it is widely used in place of insulin at far lower concentrations. Beyond bioprocessing, IGF-1 LR3 is used as a reagent for probing IGF-1 receptor signalling, PI3K and MAPK pathway activation, and the specific question of how much of native IGF-I biology is attributable to binding protein sequestration rather than to receptor pharmacology, which is precisely the comparison the analogue was built to make.

UK Peptide Lab sells IGF-1 LR3 1mg online as a lyophilised powder, dispatched from the UK. The current batch, UKPL-449, carries a certificate covering identity, HPLC purity, mass spectrometry and content, published with the supplier-reported label because the record names no independent laboratory. With an 83 residue protein the best place to confirm what you are buying is that mass spectrometry line. Orders placed before 3pm on a working day are dispatched the same day, with free UK delivery over £69.

Batch UKPL-449 tested at 98.134% purity by HPLC against a ≥98.0% specification. Mass spectrometry found [M+H]+ at 9113.0 m/z, matching the 9112.0 g/mol molecular weight, and content was 1.08mg against 1mg declared. The certificate is published in the certificate section so you can check it before ordering.

IGF-1 LR3 holds no marketing authorisation in the UK or anywhere else. UK Peptide Lab supplies it only as a reference material for in-vitro research. It is not a medicine and not for human or veterinary use. Buyers must be 18 or over and confirm research-only use. This is background, not legal advice, so check the rules for your own institution.

Both bind IGF binding proteins weakly, by opposite routes. des(1-3)IGF-I deletes the first three residues of IGF-I. IGF-1 LR3 keeps all 70, substitutes Arg3 and adds a 13 residue N-terminal extension. Francis et al. (1992) found Long [Arg3]-IGF-I and des(1-3)IGF-I were the two most potent analogues in cell lines that secrete IGFBPs.