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Research Compound Reference

IGF-1 LR3

IGF-1 LR3 is a recombinant analogue of insulin-like growth factor 1 (CAS 946870-92-4, formula C990H1528N262O300S7, average mass 9117.9), engineered to reduce binding by IGF binding proteins. It is supplied as a lyophilized powder in a sealed vial for laboratory research use only.

Also known asLong R3 Insulin-like Growth Factor-1
CAS Number946870-92-4
Molecular FormulaC400H625N111O115S9
Molecular Weight9117.60
Amino Acid Count83
Sequence83-residue recombinant IGF-1 analog with Arg substituted for Glu at position 3 and a 13-residue N-terminal extension; modifications reduce IGFBP affinity and extend circulating half-life relative to native IGF-1 (full sequence per COA).
Purity≥99% by HPLC · COA available
Physical FormLyophilized powder

What is IGF-1 LR3?

This is the largest molecule in the group and is properly a small protein rather than a peptide. The molecular reference lists the formula C990H1528N262O300S7 with an average mass of 9117.9. The seven sulfur atoms reflect the cysteines forming the internal disulfide bonds that hold the fold together, which is why the material is far more fragile than a short synthetic chain. No sequence is recorded, so none is given.

The analogue differs from native insulin-like growth factor 1 by an amino terminal extension and a substitution near that terminus. Both reduce affinity for the IGF binding protein family, which normally sequesters most of the circulating growth factor. In culture the result is a ligand that stays available to the IGF-1 receptor in serum containing medium, which is why it appears in cell expansion media and in PI3K, Akt, and MAPK signalling studies.

What is not settled includes how far reduced binding protein affinity changes receptor trafficking compared with the native ligand, and how much cross engagement of the insulin receptor and hybrid receptors contributes in different cell backgrounds.

Reconstitution & handling

Recombinant proteins of this size are handled more carefully than short peptides. Diluent is added slowly down the vial wall and the vial is left to stand, then rotated gently and never vortexed, since shear at an air liquid interface unfolds protein. Dilute acetic acid is often used for initial dissolution, since solubility is better at acidic pH. Concentration is arithmetic, so 1 mL added to a 1 mg vial gives 1 mg per millilitre.

Storage & stability

Sealed lyophilized vials are stored at -20 °C, protected from light and moisture, and equilibrated to room temperature before opening. Reconstituted solution is refrigerated at 2 to 8 °C and aliquoted into single use volumes, since repeated freezing and thawing damages a folded protein far more than a linear peptide. Reducing agents are avoided, as opening the disulfide bonds destroys the fold.

How it's tested

Each lot is assessed by reversed phase HPLC at 214 and 220 nm and by size exclusion chromatography, which reveals aggregates that reversed phase alone can miss. Mass spectrometry confirms identity against the theoretical mass of 9117.9 from C990H1528N262O300S7 and separates the oxidised form from reduced species. Endotoxin testing is relevant for cell culture material, and a lot-matched certificate is available.

Frequently asked questions

Why is this handled more carefully than a short peptide?

At 9117.9 it is a folded protein held together by disulfide bonds. Shear, foaming, and repeated freezing and thawing can unfold or aggregate it in ways a short linear chain would tolerate.

What does the LR3 designation refer to?

It denotes the long amino terminal extension and the arginine substitution near the amino terminus, the two changes that reduce affinity for IGF binding proteins in the published literature.

Why does endotoxin testing matter here?

The material is commonly used in cell culture, where endotoxin contamination confounds readouts independently of receptor signalling. It is therefore tested alongside purity and identity.

Shop lot-tested IGF-1 LR3

Third-party tested to ≥99% purity, with analytical documentation available.

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This reference describes the compound's chemistry and analytical properties for laboratory research use only. It is not medical advice; the product is not a drug, supplement, or cosmetic and is not for human or veterinary consumption.