What is IGF-1 LR3?
IGF-1 LR3 is a single-chain recombinant polypeptide belonging to the insulin-like growth factor (IGF) family of the peptide-hormone superfamily. It is a structurally modified analog of native human IGF-1, cataloged under CAS 946870-92-4 with the molecular formula C400H625N111O115S9 and a molecular weight of 9117.60. The molecule comprises 83 amino acid residues and is characterized to a purity of greater than or equal to 99% by HPLC, with a Certificate of Analysis available for each lot.
Structurally, IGF-1 LR3 differs from native IGF-1 through two defining sequence modifications: an arginine (Arg) substitution in place of the glutamate (Glu) residue at position 3, and a 13-residue extension appended to the N-terminus of the chain (the "Long R3" designation). The complete sequence is provided per the accompanying COA. Like native IGF-1, the parent scaffold contains multiple cysteine residues that form intramolecular disulfide bonds, consistent with the nine sulfur atoms reflected in its molecular formula; these bonds are integral to the folded tertiary structure of the molecule. The engineered substitutions are reported to reduce affinity for IGF-binding proteins (IGFBPs) and to extend the circulating half-life of the analog relative to native IGF-1 in research systems.
Within the scientific literature, IGF-1 and its recombinant analogs are studied as reference ligands in growth-factor signaling research, receptor-binding and IGFBP-interaction assays, and cell-culture models of proliferation and differentiation. IGF-1 LR3 is frequently used in vitro as a comparator to native IGF-1 because of its altered binding-protein profile. This material is offered strictly as a research chemical for in-vitro and laboratory investigation and is not intended for diagnostic, therapeutic, or any in-vivo use in humans or animals.
Reconstitution & handling
IGF-1 LR3 is typically supplied as a lyophilized (freeze-dried) powder that requires reconstitution into a liquid vehicle before use in laboratory work. As a disulfide-bonded polypeptide, it is commonly dissolved in a mildly acidic aqueous solvent such as dilute acetic acid or sterile water, which supports solubility of the peptide; the chosen solvent should be added slowly against the vial wall and allowed to dissolve without vigorous agitation to preserve structural integrity. Swirling gently rather than shaking helps avoid mechanical shear and foaming, both of which can promote denaturation or aggregation of higher-molecular-weight peptides.
For assay work, an acidic stock is often further diluted into a compatible neutral buffer or carrier (for example, a buffer containing a stabilizing carrier protein) immediately prior to use, since the peptide is generally more stable in acidic stock than in dilute neutral solution. Reconstitution should be performed under clean conditions, and the resulting solution inspected to confirm it is clear and free of visible particulates. All handling parameters described here concern the chemistry of dissolving and preparing the material for in-vitro research and do not constitute administration guidance.
Storage & stability
In its lyophilized form, IGF-1 LR3 is best kept sealed, protected from light and moisture, and stored frozen for long-term stability; short intervals at refrigerated or ambient temperature during shipping and handling are generally tolerated by the dry powder. Once reconstituted, the peptide is markedly less stable in solution and should be held cold (refrigerated for near-term use) with longer-term storage of aliquots in a freezer. Preparing single-use aliquots is recommended to minimize repeated freeze-thaw cycles, which can degrade disulfide-bonded polypeptides and reduce measured purity. Avoiding repeated warming, exposure to light, and prolonged residence in dilute neutral solution helps preserve the integrity of the material over its usable life.
How it's tested
The identity and purity of IGF-1 LR3 are verified analytically and documented on a lot-specific Certificate of Analysis (COA). Reversed-phase high-performance liquid chromatography (HPLC) is used to quantify chromatographic purity, with this material characterized at greater than or equal to 99%; the HPLC trace resolves the primary peptide peak from process-related and degradation-related impurities. Mass spectrometry (MS) is applied to confirm molecular identity by comparing the observed mass against the theoretical molecular weight of 9117.60 derived from the C400H625N111O115S9 formula. Additional characterization may include assessment of net peptide content and residual solvent or counter-ion profiles. Together these orthogonal methods establish that a given lot matches its stated identity and purity specifications before release for research use.