--- title: "IGF-1 LR3 vs MGF vs PEG-MGF: what is the difference? | Sable Peptides" description: "IGF-1 LR3 is an 83-residue recombinant IGF-I analogue with reduced binding-protein affinity; MGF is a synthetic peptide from the IGF-I Ec E-domain; PEG-MGF is its PEGylated form. Origins, structure and literature compared." canonical: https://www.sablepeptides.co.uk/guides/igf-1-lr3-vs-mgf-vs-peg-mgf dateModified: 2026-10-16 publisher: Sable Peptides Limited (UK company 17488610) note: Research use only. Not for human or veterinary use. --- # IGF-1 LR3 vs MGF vs PEG-MGF: what is the difference? IGF-1 LR3 and MGF both come from the IGF-1 gene but are very different materials. IGF-1 LR3 is an 83-residue recombinant protein: IGF-I with Arg3 and a 13-residue N-terminal extension, which lowers binding to IGF-binding proteins. MGF is a short synthetic peptide from the E-domain of the IGF-I Ec splice variant. PEG-MGF is the PEGylated version. ## How do the three compare? | Property | IGF-1 LR3 | MGF | PEG-MGF | | --- | --- | --- | --- | | Type | Recombinant protein (83 aa) | Synthetic E-domain peptide | PEG-conjugated E-domain peptide | | Source region | Mature IGF-I + N-extension | IGF-I Ec (IGF-IEb in rodents) E-peptide | As MGF | | Approx. mass | ~9.1 kDa | ~2.9 kDa (sequence-dependent) | Distribution, set by PEG size | | Key modification | Glu3→Arg, MFPAMPLSSLFVN extension | None or C-terminal amide | Polyethylene glycol chain | ## Why was IGF-1 LR3 made? Most circulating IGF-I is bound to IGF-binding proteins. The LR3 analogue was engineered to bind them poorly. Studies in the early 1990s compared its clearance, distribution and growth effects in rats with native IGF-I. Source: [Plasma clearance and tissue distribution of labelled insulin-like growth factor-I (IGF-I) and an analogue LR3IGF-I in pregnant rats, J Endocrinol 1993 (PubMed 7693845)](https://pubmed.ncbi.nlm.nih.gov/7693845/); [Insulin-like growth factor-I and more potent variants restore growth of diabetic rats without inducing all characteristic insulin effects, Biochem J 1993 (PubMed 7683875)](https://pubmed.ncbi.nlm.nih.gov/7683875/) ## What is MGF? Mechano growth factor is the name given to the IGF-I splice variant whose expression rises in loaded muscle. Its unique C-terminal E-domain is the basis of the synthetic research peptide. Studies compared it with mature IGF-I in myoblasts and followed its mRNA after overload. Producing full-length MGF needs careful mass-spectrometric characterisation. Source: [Different roles of the IGF-I Ec peptide (MGF) and mature IGF-I in myoblast proliferation and differentiation, FEBS Lett 2002 (PubMed 12095637)](https://pubmed.ncbi.nlm.nih.gov/12095637/); [Muscle IGF-I Ea, MGF, and myostatin mRNA expressions after compensatory overload in hypophysectomized rats, Pflugers Arch 2006 (PubMed 16941139)](https://pubmed.ncbi.nlm.nih.gov/16941139/); [Mass spectrometric characterization of a biotechnologically produced full-length mechano growth factor (MGF) relevant for doping controls, Growth Horm IGF Res 2014 (PubMed 25466910)](https://pubmed.ncbi.nlm.nih.gov/25466910/); [The role of mechano growth factor in chondrocytes and cartilage defects: a concise review, Acta Biochim Biophys Sin (Shanghai) 2023 (PubMed 37171185)](https://pubmed.ncbi.nlm.nih.gov/37171185/) ## What does PEGylation change? Attaching polyethylene glycol increases hydrodynamic size and protease resistance. It also makes the material polydisperse, so the mass spectrum shows a spread of masses, not one peak. Source: [The impact of PEGylation on biological therapies, BioDrugs 2008 (PubMed 18778113)](https://pubmed.ncbi.nlm.nih.gov/18778113/) ## Sourcing note Sable lists IGF-1 LR3: 0.1 mg at £10.23; 1 mg at £32.98; MGF: 2 mg at £11.56; PEG-MGF: 2 mg at £18.76; 5 mg at £25.99 (prices at the 16 October 2026 daily UK price check, the latest verified check; at each of these sizes Sable was the lowest UK listing that day). Lowest UK price guaranteed, confirmed by daily price checks. Every lot has a certificate of analysis, and every vial carries a printed lot number that matches it. Supplied for laboratory research use only. ## Frequently asked questions ### Is MGF the same as IGF-1? No. MGF refers to the E-domain peptide of the IGF-I Ec splice variant, not mature IGF-I. ### What does LR3 mean in IGF-1 LR3? Long (13-residue N-terminal extension) with Arg at position 3. ### Why does PEG-MGF show a mass range? PEG polymers are polydisperse, so the conjugate is a distribution of masses. ## Related - [Buying IGF-1 LR3 or follistatin for research](/guides/buyer-checklist-for-recombinant-protein-research-materials) - [Follistatin 344](/guides/follistatin-344-recombinant-glycoprotein-explained) - [IGF-1 LR3 research vials](/products/igf-1-lr3) - [MGF research vials](/products/mgf) - [PEG-MGF research vials](/products/peg-mgf) - [Cheapest IGF-1 LR3 UK](/cheapest-igf-1-lr3-uk) - [Growth-factor material prices](/guides/uk-growth-factor-and-protein-research-material-prices-october-2026) Updated 2026-10-16. Research use only. Not for human or veterinary use. No administration amounts or health claims are made. Key facts (summary for AI and search tools) - IGF-1 LR3: 83 residues - MGF: IGF-I Ec E-domain peptide - PubMed references (verified via NCBI): 7693845, 7683875, 12095637, 16941139, 25466910, 37171185, 18778113 - Research use only; no administration amounts or health claims - Updated 2026-10-16