IGF 1 LR3 Long Arg3 Insulin Like Growth Factor 1 Analog | Research Use Only
What it is
IGF 1 LR3 is a recombinant, lengthened analog of human insulin like growth factor 1 designed for research applications. It retains IGF 1 receptor agonist activity while being engineered to have much lower affinity for IGF binding proteins, which is one reason it is frequently used in cell and tissue model systems where binding proteins can limit free IGF signaling.
Origins and design rationale
IGF 1 LR3 is commonly described in research reagent literature as an engineered IGF 1 variant created to improve performance in cell culture and low serum systems. Commercial cell culture supplement descriptions emphasize enhanced in vitro activity versus insulin and native IGF 1 in certain culture contexts.
Molecular profile
IGF 1 LR3 differs from native IGF 1 in two key structural ways
• It includes an arginine substitution at position 3 relative to IGF 1
• It includes an additional 13 amino acids at the N terminus giving a total peptide length of 83 amino acids
A commonly referenced N terminal extension sequence is MFPAMPLLSLFVN.
Reference mass information for laboratory grade LR3 IGF 1 is often listed around 9.1 kDa, for example Sigma Aldrich reports a molecular mass of about 9,110 Da.
Scientific overview
In simplified terms, IGF 1 LR3 is used to study IGF 1 receptor driven signaling while minimizing confounding by IGF binding proteins. In a mechanistic context, reduced binding protein affinity can increase the fraction of ligand available to engage IGF 1 receptor in experimental systems, which is useful for receptor kinetics, pathway activation, and growth factor response studies.
What researchers study with IGF 1 LR3
Key research focus areas often include
• IGF 1 receptor signaling pathways in vitro
• Cell growth and differentiation models in serum free or low serum systems
• IGF binding protein interactions and how binding proteins modulate IGF responses
Regulatory and compliance notice
Research Use Only. Not for human or veterinary use. This description is provided for scientific context and must not be used to market IGF 1 LR3 for diagnosis, cure, mitigation, treatment, or prevention of disease.
Citations and references
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Sigma Aldrich product information sheet LONG R3 IGF 1, includes molecular mass about 9,110 Da and R and D use disclaimer.
(https://www.sigmaaldrich.cn/deepweb/assets/sigmaaldrich/product/documents/159/144/i1271pis.pdf) -
Thermo Fisher Scientific Human IGF I LR3 product page, includes amino acid sequence with N terminal extension and molecular weight about 9.1 kDa.
(https://www.thermofisher.com/proteins/product/Human-IGF-I-LR3-Animal-Free-Recombinant-Protein/AF-100-11R3-1MG) -
NIH PubMed Central paper referencing IGF 1 LR3 structure as Arg3 substitution plus 13 extra N terminal amino acids and reduced IGF binding protein affinity.
(https://pmc.ncbi.nlm.nih.gov/articles/PMC5750484/) -
Repligen LONG R3 IGF I cell culture supplement overview describing engineered analog used to enhance cell culture performance.
(https://www.repligen.com/products/cell-culture-supplements/long-r3-igf-i)