IGF-LR3

Note on the two modifications

Two changes separate this molecule from native IGF-1. An arginine replaces the glutamate at position 3, which is the source of the R3 designation, and a thirteen-residue N-terminal extension gives the Long. Together they sharply reduce affinity for the IGF binding proteins that sequester circulating IGF-1 while leaving receptor binding largely intact. That is the design rationale, and it is why this analogue became a standard reagent for serum-free mammalian cell culture rather than a therapeutic candidate.

Two corrections, because both errors appear widely on competing listings. The substitution is glutamate to arginine, not arginine to leucine. And the frequently repeated claim of a dramatically extended half-life is contested: reduced binding-protein affinity cuts both ways, since the IGFBP-3 complex also slows clearance of native IGF-1, and some animal work reports faster clearance rather than slower. No human pharmacokinetic study of this analogue has been published.

02

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Certificate of analysis - lot IGFR-052026-2

Lot record

IGFR-052026-2

Results, this lot

Purity, content and endotoxin figures above are specific to lot IGFR-052026-2 and are not specifications carried across other lots. Each lot is tested individually and reports its own results. The certificate supplied with your unit records the results for that lot.

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Panels differ between products and between lots. What follows is the scope of testing performed on this lot. Nothing is claimed unless it appears on the certificate for the lot supplied.

The first three entries in the right-hand column are the ones that matter on a recombinant protein; see section 04. Where a parameter is material to intended laboratory work, purchasers should verify it independently or source material released against that specification.

04

This is the section that matters most here, and it is the one competing listings do not carry.

IGF-1 and its analogues carry three disulfide bonds. Recombinant expression in bacteria yields material that can include misfolded disulfide isomers with the correct sequence, the correct mass, and substantially reduced activity. A reversed-phase purity figure will not reliably separate those from correctly folded protein, and a mass confirmation will not flag them either, because the mass is identical. The specifications that speak to folding are SDS-PAGE run under both reducing and non-reducing conditions, size-exclusion chromatography for aggregates and dimers, and a cell-based potency assay reported as an ED50. None of those appears on this certificate.

Endotoxin is the second question, and on this lot it has been answered. Anything expressed in E. coli carries bacterial endotoxin unless it is specifically removed and specifically tested for, and endotoxin contamination will confound a cell-based readout regardless of how pure the protein is. This lot was tested by limulus amebocyte lysate assay under USP in duplicate, with both replicates passing at an assay sensitivity of 0.05 endotoxin units per millilitre. Panels vary between lots, so confirm it on the certificate for the unit supplied rather than assuming it carries across.

The honest summary: identity, purity, content and endotoxin are covered on this lot. Folding, aggregation and bioactivity are not. We state that rather than let a purity percentage answer questions it does not answer. Researchers whose work depends on those parameters should source material released against them.

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Preparation conditions are the responsibility of the receiving laboratory. Verum provides no protocol, no preparation instruction, and no guidance on use.

06

The primary literature specific to this analogue is small, and most of it comes from one Australian group working in the early 1990s. That is because the molecule was designed as a reagent rather than a drug candidate, so it never accumulated the publication record a therapeutic programme would generate. Entries are indexed by the experimental system used, and each description states what the study measured rather than what it concluded. No human pharmacokinetic or clinical study of this analogue has been published. Verum has no involvement in any of this work and makes no representation as to its applicability.

One further point worth stating plainly: the industry-standard potency assay for this protein measures proliferation of a human breast cancer cell line, with an ED50 in the sub-nanogram-per-millilitre range. That is the assay by which reference-grade material is released. Work conducted in culture and in rodents does not establish an effect in any other system.

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08

By placing an order you confirm each of the following:

Confirmation is recorded at checkout against your order. Verum reserves the right to decline or cancel any order.

09

Orders placed before the daily cutoff are dispatched the same day from our United States warehouse. Domestic orders typically arrive within two business days. A tracking reference is issued by email once the consignment leaves the facility. Each unit carries a scannable code linking to the certificate for its own lot.

Not for human or veterinary use. Not for use in diagnostic or therapeutic procedures. This product is a laboratory reagent. Nothing on this page constitutes medical advice, a recommendation for personal use, or a representation that this material is safe or effective for any purpose. No statement here has been evaluated by the U.S. Food and Drug Administration.