MGF — mechano growth factor — is a 24-amino-acid peptide corresponding to the C-terminal E-domain of IGF-1 Ec, a splice variant of the IGF-1 gene that skeletal muscle upregulates after mechanical loading and damage. It is not an IGF-1 analogue and it is not a receptor agonist at IGF-1R. It is the tail end of a precursor protein, and the research interest in it rests on a single striking observation: the isolated E-domain peptide retains activity of its own, distinct from the mature IGF-1 it is normally cleaved away from.
MyPeptide supplies MGF (Mechano Growth Factor) as a lyophilized powder in 2 mg and 5 mg vials within the IGF and muscle peptides range. Supplied for laboratory research only; not for human or veterinary use.
What is MGF?
The IGF-1 gene does not produce a single protein. Alternative splicing generates several pro-IGF-1 transcripts that share the same 70-residue mature IGF-1 sequence but differ in the C-terminal extension, called the E-domain. The IGF-1 Ec variant — the one whose expression rises sharply in loaded or damaged muscle — carries an E-domain that includes a 49-base insert shifting the reading frame and producing a unique C-terminal sequence. The 24-residue peptide reproduced synthetically as MGF corresponds to that unique region.
The sequence supplied is Tyr-Gln-Pro-Pro-Ser-Thr-Asn-Lys-Asn-Thr-Lys-Ser-Gln-Arg-Arg-Lys-Gly-Ser-Thr-Phe-Glu-Glu-Arg-Lys, with CAS number 62031-54-3 and a molecular weight of 2,867.10 g/mol. The high arginine and lysine content gives the peptide a strongly basic character, which is relevant to how it behaves in solution and on a chromatography column.
Origin and structure
The splice variant was characterised by Geoffrey Goldspink's group at the Royal Free Hospital in the 1990s, working on how muscle senses and responds to mechanical load. The name captures the finding rather than the chemistry: expression of this transcript rose after stretch and eccentric loading in rodent muscle, ahead of the systemic IGF-1 response, suggesting a locally produced signal.
Two structural points matter for anyone reading the literature. First, the human and rodent E-domain sequences differ, so results are not automatically transferable between species — a recurring source of confusion in secondary summaries. Second, MGF as sold is a synthetic fragment of a precursor protein, not a naturally circulating hormone; in vivo the E-domain is cleaved from pro-IGF-1 during processing, and whether the free peptide persists at meaningful concentrations in tissue remains an open question in the field.
How MGF is thought to work
No receptor has been identified for MGF. This is the central caveat in its mechanism, and any account that names a specific receptor is going beyond the published record. What the literature does report is a set of cell-level observations: in cultured myoblasts, the E-domain peptide has been reported to promote proliferation and to delay differentiation into myotubes, a pattern opposite to that of mature IGF-1, which favours differentiation. That divergence is the strongest argument that the E-domain acts through its own route rather than by weak IGF-1R agonism.
Proposed mechanisms in the literature include an interaction with the cell membrane driven by the peptide's basic charge, nuclear or nucleolar localisation reported in some cell studies, and effects on satellite cell activation that would fit the mechanical-loading biology the peptide was named for. These are hypotheses supported by cell-culture data, not an established mechanism.
A practical consequence of having no receptor and a small, highly charged, unstructured sequence is very short persistence. Reported in-solution and in-serum stability is on the order of minutes, which is the specific problem the PEGylated variant was created to address.
What the research has examined
Myoblast proliferation and differentiation
The core in-vitro literature uses C2C12 and primary human myoblasts to compare the E-domain peptide against mature IGF-1. Reported findings include increased proliferation markers and delayed fusion into myotubes, consistent with a role in expanding the satellite cell pool before differentiation begins.
Mechanical loading and expression studies
A larger and more robust body of work does not use synthetic peptide at all: it measures IGF-1 Ec transcript levels in muscle after resistance exercise, stretch or injury in rodents and in human biopsy studies. These expression data are what established the loading response; they say nothing directly about what administering the synthetic peptide does.
Tissue repair and cardiac models
Rodent studies have examined E-domain peptide administration in muscle injury and in cardiac infarct models, reporting changes in cell survival and regeneration markers. This is preclinical and exploratory work with small study numbers.
Stability and formulation comparisons
Because the native peptide clears so quickly, a distinct line of work compares it with the PEGylated form. Our MGF vs PEG-MGF comparison sets out how that choice affects experimental design.
Forms and sizes we supply
| Attribute | Specification |
|---|---|
| Product | MGF (Mechano Growth Factor) |
| Also known as | IGF-1 Ec E-domain peptide, MGF C-terminal peptide |
| Form | Lyophilized powder, sealed glass vial |
| Available sizes | 2 mg, 5 mg |
| Purity | ≥99% by HPLC, lot-matched COA available |
| CAS number | 62031-54-3 |
| Molecular weight | 2,867.10 g/mol |
| Residue count | 24 amino acids |
| Sequence | Tyr-Gln-Pro-Pro-Ser-Thr-Asn-Lys-Asn-Thr-Lys-Ser-Gln-Arg-Arg-Lys-Gly-Ser-Thr-Phe-Glu-Glu-Arg-Lys |
| Known receptor | None identified in the published record |
| Intended use | Laboratory research only |
The 2 mg vial fits short in-vitro series; the 5 mg vial is the more economical unit where an extended study should run on a single lot. Because the peptide is short-lived in solution, most laboratories prefer more, smaller aliquots over one large stock. Sourcing checks are set out in our MGF buying guide, and the longer-persisting alternative is PEG-MGF.
Reconstitution and storage in a lab context
MGF reconstitutes readily in bacteriostatic or sterile water; its basic residues make it comfortably water-soluble, and mildly acidic buffers also appear in the literature. Solvent is added down the vial wall onto the cake and the vial swirled rather than shaken, since agitation of a 24-residue peptide produces foam and increases surface denaturation without speeding dissolution.
The arithmetic is a laboratory calculation, not a protocol: a 5 mg vial made up with 2 mL of diluent gives 2.5 mg/mL, or 2,500 mcg/mL, so 0.1 mL — the 10-unit mark on a U-100 syringe — contains 250 mcg. The same vial made up with 5 mL gives 1 mg/mL and 100 mcg per 0.1 mL. The method is in our reconstitution guide.
Lyophilized vials sit at −20 °C, sealed and protected from light and moisture. Reconstituted MGF has a short working window at 2–8 °C; for anything beyond a few days, aliquoting and freezing is standard, and repeated freezing and thawing should be avoided. Broader practice is covered in how to store peptides.
Purity, COA and how to read it
Two entries carry the weight on an MGF certificate. The HPLC trace gives purity as main-peak area, and for a basic 24-mer the shoulders matter: deletion sequences differing by one residue elute close to the main peak, so a clean, symmetrical peak is more informative than the headline percentage alone. Mass spectrometry should return an observed mass consistent with 2,867.10 g/mol; a value 17 Da low would point to a deamidation or truncation problem worth querying.
The counter-ion should also be stated. Reversed-phase purification usually leaves peptides as a TFA salt, and for a peptide this basic the salt fraction is not trivial — it affects how much peptide is actually in a nominally 5 mg vial. Our guide to reading a peptide certificate of analysis covers each section in turn.
Regulatory status
MGF has no marketing authorisation as a medicine in the United States or elsewhere, no reference-listed product and no approved labelling. It is supplied as a research-use-only chemical for laboratory investigation by qualified personnel — not a supplement, not a medicine, and not for human or veterinary administration. IGF-1 and its splice-variant peptides are prohibited in sport under anti-doping rules.
Related peptides and further reading
The direct alternative is PEG-MGF, the same core peptide with a polyethylene glycol chain attached to extend its working life. The receptor-active members of the family are IGF-1 LR3 and IGF-1 DES (1-3), which act at IGF-1R and therefore answer a different question from the E-domain peptide. Wider context on the tissue biology is in our skeletal muscle research hub.