Two changes are hidden in one short name
The Sigma product-information reference for LONG R3 IGF-1 describes replacement of Glu at position 3 with Arg and a 13-amino-acid N-terminal extension. This explains the long and R3 elements of the name. It does not describe the production route or measured properties of this site’s material.
Write the extension and substitution as separate identity fields. That makes it easier to detect a proposal for native IGF-1, a different analogue or an incompletely described product.
Numbering needs a reference sequence
After an extension is added, numbering from the native region and numbering from the beginning of the extended chain differ. A statement such as residue 3 can be misleading unless the reference is clear. Ask the supplier to identify both the mature native reference and the complete analogue sequence.
This is especially important when connecting a publication, structural annotation and analytical expectation. Keep the numbering map in the file so a later reviewer does not interpret a correct native-region substitution as a different position in the full chain.
| Field | What LR3 refers to | Request to keep explicit |
|---|---|---|
| Extension | Additional N-terminal residues | Complete offered sequence |
| R3 | Arg substitution in native-region numbering | Reference and position map |
| Structure | Analogue identity | Relevant structural characterization |
| Supplied format | Actual formulation and quantity basis | Supplier-specific confirmation |
Sequence identity and structural state are different questions
A complete residue string is necessary but may not be sufficient for a structured research material. Ask what evidence addresses the project’s relevant structural features and what the identity report actually measures. A mass comparison is not a universal demonstration of folding or experimental activity.
The cited reference describes one supplier’s material. Do not copy its expression system, formulation or handling instruction into another supplier’s specification unless those details have been independently confirmed for the offered product.
Plan a comparison without assuming the outcome
For an illustrative cell-research comparison, create separate lines for native material and LR3 analogue. Keep sequence, amount basis, formulation and documentation visible on both. The laboratory should choose the controls and readouts appropriate to its question; the purchasing file records which defined materials were selected.
If a reported result differs, first verify the material definitions and the experimental conditions. The catalogue name alone does not explain the result. An analogue relationship is a reason to compare carefully, not a promise that either material will produce a particular outcome.
Questions buyers ask
Is LR3 the same molecule as native IGF-1?
No. The extension and substitution define an analogue with a different sequence.
Does a matched molecular mass prove assay activity?
No. The scope of mass evidence is not the same as a functional measurement. The laboratory must assess evidence for its intended question.
Your next step
Ask for a full analogue sequence and a native-reference numbering map. Confirm offered format and relevant analytical evidence separately.
Related reading: IGF-1 LR3 catalog entry; research supplier questions.
AI-assisted educational guide prepared from the cited sources. No testing of a supplied batch is reported here. For research-material purchasing, not medical guidance or instructions for human use. Confirm the actual offered material and available evidence before ordering.
