IGF-1 LR3 for Laboratory Research

IGF-1 LR3 is a synthetic recombinant analogue of IGF-I comprising 83 amino-acid residues. The construct combines a 13-residue N-terminal extension, MFPAMPLSSLFVN, with a Glu3→Arg substitution inside the mature IGF-I domain. Mature native human IGF-I contains 70 residues; that native sequence boundary and the two LR3 modifications must be kept separate when assigning literature or analytical results.

Laajoki and colleagues investigated the solution structure and backbone dynamics of Long-[Arg3]IGF-I by NMR. This provides structural evidence for the named construct, not authentication of supplied material. A product designation, complete sequence, declared molecular form, batch code and analytical record must refer to the same material before a batch is assigned to a study.

The calculated formula and mass describe the stated sequence and disulphide assumption; they do not identify a physical sample. UniProt P05019 concerns native human IGF-I and is not an LR3 accession. Likewise, the absence of a compound-specific PubChem CID is a database finding rather than evidence about a batch.

Structural source: Laajoki et al. 2000 · PMID 10744677

The IGF system comprises ligands, receptors and IGF-binding proteins. Within this system, receptor activation and binding-protein association are different measurements. A change in affinity for one binding protein under one assay configuration cannot be converted into a universal statement about receptor activity, biological availability or response.

Heding and colleagues associated N-terminally modified analogues with lower affinity for the tested IGFBP-3 configuration. Grimes and colleagues compared IGF-I, Des(1–3)IGF-I and LR3 in ovarian granulosa-cell culture while measuring IGFBP-2 and IGFBP-3 production and IGFBP-3 mRNA. Thomas and colleagues examined IGFBP-2/-3 localisation and expression alongside other endpoints in an in vitro bovine follicle model. Together, these records show why the analyte, binding protein, species, sample and assay must stay attached to every interpretation.

Native IGF-I pathway studies remain context only. Rommel and colleagues measured PI3K/Akt/mTOR and PI3K/Akt/GSK3 relationships in mouse myotube culture, while Stitt and colleagues examined FOXO factors and ubiquitin ligases in cell and animal models. Bailes and Soloviev reviewed the wider ligand, receptor and binding-protein network. None of these three publications is a primary measurement of LR3.

Target-system sources: Heding et al. 1996 · PMID 8662901 · Grimes et al. 1992 · PMID 1379161 · Voorhamme et al. 2006 · PMID 17172665 · Thomas et al. 2007 · PMID 17636166 · Rommel et al. 2001 · PMID 11715022 · Stitt et al. 2004 · PMID 15125842 · Bailes & Soloviev 2021 · PMID 33557137

This section describes findings in controlled research and makes no statement about use. The records span isolated-protein methods, cell and tissue systems, and preclinical animal models. They must be read by analyte, model, species, method and measured endpoint rather than treated as one undifferentiated evidence set.

No human intervention record for IGF-1 LR3 is represented in this evidence map. Cell-line, isolated-tissue and animal measurements do not establish outcomes in another model or certify a supplied batch.

Study sources: PMID 1379161 · PMID 8662901 · PMID 10744677 · PMID 11181549 · PMID 17172665 · PMID 17636166 · PMID 19258508 · PMID 7561636 · PMID 9488001 · PMID 33587816

IGF-1 LR3, R3-IGF-I and Des(1–3)IGF-I are separate molecular forms. IGF-1 LR3 carries both the 13-residue N-terminal extension and the Glu3→Arg substitution. R3-IGF-I carries the position-3 substitution without the Long R3 extension. Des(1–3)IGF-I lacks the first three residues of mature IGF-I. Native IGF-I has neither of these analogue definitions.

This distinction matters in two linked but separate domains. In binding research, an N-terminal change can alter an analogue's measured interaction with a named IGFBP under a defined assay. The Heding biosensor record concerns recombinant unglycosylated IGFBP-3 and cannot be generalised to all IGFBPs. Grimes compared several molecular forms in one granulosa-cell system, but a comparative response does not collapse their identities.

In analytical research, the intact mass, N-terminal structure and possible degradation products create a different problem. Mongongu and colleagues used immunopurification with high-resolution mass spectrometry to distinguish intact LongR3-IGF-I, Des(1–3)IGF-I, R3-IGF-I and N-terminal degradation products. That study demonstrates method-specific analytical discrimination; it does not authenticate any Reborn batch.

A defensible batch record therefore preserves an explicit chain: declared analogue name, complete sequence, expected molecular form, batch code, identity method and result. HPLC can report a chromatographic profile or method-specific purity result, but retention behaviour alone should not be treated as proof that the intact analyte is LR3 rather than a related analogue. Conversely, a mass result addressing identity does not automatically establish chromatographic purity. Both questions remain method- and batch-specific.

The spellings “IGF-1 LR3”, “Long R3 IGF-I” and “Long-[Arg3]insulin-like growth factor-I” can identify the same 83-residue construct when the sequence definition agrees. The labels R3-IGF-I and Des(1–3)IGF-I cannot. Terminology is therefore part of sample traceability, not merely editorial style.

Analogue-distinction sources: Mongongu et al. 2021 · PMID 33587816 · Heding et al. 1996 · PMID 8662901 · Grimes et al. 1992 · PMID 1379161

Physical form, stated content, storage conditions and stability period must be reconciled against the released label, specification and documentation for the applicable batch. None is inferred from the molecular literature. If a released record describes the material as lyophilised, that word specifies presentation only; it does not establish sequence identity, content, stability or purity.

The documentation chain should connect product designation, batch code, analytical method, test date and result. The analyte description must identify the 83-residue Long R3 construct rather than R3-IGF-I, Des(1–3)IGF-I or native IGF-I. Any discrepancy among label, specification and COA should be resolved before the material is described as a matter of fact or assigned to an experiment.

Any numerical purity statement applies only to the tested batch and the stated analytical method. HPLC and molecular-identity testing answer different questions. High-resolution mass spectrometry may support discrimination among intact analogue forms and N-terminal variants in a validated workflow, while an HPLC result describes the chromatographic measurement reported for that batch. Neither result should be transferred to another batch.

Analytical context: Mongongu et al. 2021 · PMID 33587816 · Laajoki et al. 2000 · PMID 10744677

IGF-1 LR3 is supplied to laboratories in the EU as research material. Literature records define research questions and model-specific measurements; they do not certify the identity, content, physical form, purity or stability of supplied material. Those properties require the released specification, label and batch documentation.

Experimental findings must remain attached to the named analogue, model and endpoint. Results involving native IGF-I, a related analogue, isolated protein, cultured cells, tissue or an animal model are not interchangeable and do not predict an outcome outside the stated system.

Research use only. For laboratory research only. Not for human or veterinary use. Not intended to diagnose, treat, cure or prevent any disease. Not a medicinal product, food or cosmetic.