PEG-MGF is mechano growth factor — the 24-residue C-terminal E-domain peptide of the IGF-1 Ec splice variant — with a polyethylene glycol chain covalently attached to slow its clearance. The peptide sequence is unchanged; the modification exists solely to solve a handling and pharmacokinetic problem. Native MGF is reported to persist in solution and in serum for minutes, which makes any experiment involving more than an immediate, local exposure difficult to design. PEGylation extends that window substantially and is the whole reason the variant exists.
MyPeptide supplies PEG-MGF 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 PEG-MGF?
Two components make up the molecule. The peptide core is the same sequence supplied as MGF: Tyr-Gln-Pro-Pro-Ser-Thr-Asn-Lys-Asn-Thr-Lys-Ser-Gln-Arg-Arg-Lys-Gly-Ser-Thr-Phe-Glu-Glu-Arg-Lys, corresponding to the unique C-terminal region produced when the IGF-1 gene is spliced to the Ec variant that muscle upregulates after mechanical loading. The second component is a polyethylene glycol polymer, conjugated to a reactive site on the peptide — most commonly an N-terminal amine or a lysine side chain.
Because the PEG chain is a polymer rather than a defined molecule, PEG-MGF has no single CAS number and no single molecular weight. The mass depends on the polymer length used, which is why the specification for this product states that molecular weight is given on the lot certificate rather than as a fixed catalogue value. That is a genuine property of PEGylated products, not a gap in the paperwork.
Origin and structure
PEGylation is a general protein-chemistry strategy that predates its application to MGF by decades; it is the same approach used in approved biologics such as pegfilgrastim and peginterferon. Attaching a hydrophilic polymer chain increases the molecule's hydrodynamic radius, which slows renal filtration, and physically shields the peptide backbone from proteases and from receptor or antibody surfaces.
The trade-off is intrinsic to the method. The same steric shielding that protects the peptide also reduces its accessibility, so PEGylated molecules routinely show lower activity per molecule in an in-vitro assay than the unmodified parent, while performing better where persistence matters. This is well documented across the PEGylated-biologic literature and should be assumed for PEG-MGF unless a specific study shows otherwise.
A second structural consideration is heterogeneity. Unless the conjugation chemistry is strictly site-specific, a PEGylated peptide preparation contains a distribution of species — mono- and di-PEGylated forms, and positional isomers — rather than a single compound. This affects how the analytical certificate should be read.
How PEG-MGF is thought to work
The proposed biological activity is that of the peptide core, and the important caveat carries over unchanged: no receptor has been identified for the MGF E-domain peptide. Cell-culture work reports that the E-domain promotes myoblast proliferation and delays differentiation into myotubes — a pattern opposite to that of mature IGF-1, which favours differentiation. That divergence is the main argument that the E-domain acts through a route of its own rather than through weak IGF-1 receptor agonism. Proposed routes include charge-driven membrane interaction and nuclear localisation reported in some cell studies; none is established.
What PEGylation changes is exposure, not signalling. In a research context the practical consequence is that PEG-MGF supports experiments with a longer, flatter exposure profile, while native MGF supports experiments needing a short, sharply defined pulse — for example when the question is about the timing of satellite cell activation rather than its magnitude. The half-life difference is the design variable, and our MGF vs PEG-MGF comparison works through the selection logic.
What the research has examined
Myoblast and satellite cell studies
Cell-culture work on the E-domain peptide, whether PEGylated or not, has focused on proliferation markers, delayed fusion into myotubes, and satellite cell activation in primary and C2C12 systems. These are in-vitro readouts.
Muscle injury and regeneration models
Rodent studies have administered E-domain peptide in crush, cardiotoxin and eccentric-damage muscle models, reporting changes in regeneration markers and fibre cross-sectional area. Study numbers are small and results have not been replicated at scale; this remains exploratory preclinical work.
Pharmacokinetic and formulation comparisons
The most directly relevant literature for PEG-MGF specifically is not about muscle biology at all — it is the general PEGylation literature on clearance, immunogenicity and activity trade-offs, which is mature and well replicated. Our guide to peptide stability and half-life covers why DAC, PEG and acetylation modifications exist and what each buys.
Expression-level work on IGF-1 Ec
The strongest evidence associating this splice variant with mechanical load comes from transcript-level studies in loaded rodent and human muscle. Those data motivated interest in the peptide but do not themselves describe what administering it does.
Forms and sizes we supply
| Attribute | Specification |
|---|---|
| Product | PEG-MGF |
| Core peptide | MGF, the 24-residue C-terminal E-domain of IGF-1 Ec |
| Core 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 |
| Modification | Covalently attached polyethylene glycol chain |
| Form | Lyophilized powder, sealed glass vial |
| Available sizes | 2 mg, 5 mg |
| Purity | ≥99% by HPLC, lot-matched COA available |
| Molecular weight | Varies with PEG chain length; stated on the lot certificate |
| Known receptor | None identified for the peptide core |
| Intended use | Laboratory research only |
One point deserves attention when planning molar calculations: for a conjugate, a stated 5 mg is not 5 mg of peptide. Part of that mass is polymer, so the peptide-equivalent content is lower and depends on the PEG length. Where a study needs molar equivalence between PEG-MGF and native MGF arms, the peptide content on the certificate is the figure to work from, not the vial label. Ordering considerations are covered in our PEG-MGF buying guide.
Reconstitution and storage in a lab context
PEGylation improves aqueous handling, and PEG-MGF dissolves readily in bacteriostatic or sterile water. Solvent is directed down the vial wall onto the cake and the vial swirled gently; PEGylated material foams easily, and foam makes accurate withdrawal harder rather than indicating a problem with the peptide.
The arithmetic is a laboratory calculation: a 5 mg vial made up with 2 mL of diluent yields 2.5 mg/mL, or 2,500 mcg/mL of conjugate, so 0.1 mL — the 10-unit mark on a U-100 syringe — contains 250 mcg of conjugate. Converting that to peptide-equivalent requires the certificate figure noted above. The general procedure is set out in our reconstitution guide.
Lyophilized vials are stored at −20 °C, sealed and protected from light and moisture. Reconstituted material holds at 2–8 °C for short-term work; longer studies use frozen aliquots, with repeated freezing and thawing avoided. Wider practice is covered in how to store peptides.
Purity, COA and how to read it
A conjugate certificate is read differently from a plain peptide certificate. Three entries matter most. First, the degree of PEGylation and the polymer molecular weight — without these the molar content of the vial cannot be calculated. Second, the distribution of species: a mono-PEGylated preparation and a mixed mono/di preparation are not the same reagent, and HPLC or SDS-PAGE should show which one is in the vial. Third, free peptide content, since unconjugated MGF behaves entirely differently in an experiment.
Purity by area percentage remains useful but is less decisive here, because a broad polymer distribution can present as a wide peak without indicating contamination. Our guide to reading a peptide certificate of analysis explains how the HPLC and mass spectrometry sections relate.
Regulatory status
PEG-MGF has no marketing authorisation as a medicine anywhere, 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 fall under the growth-factor prohibitions in sport anti-doping rules.
Related peptides and further reading
The unmodified parent is MGF. The receptor-active members of the same family, IGF-1 LR3 and IGF-1 DES (1-3), act at IGF-1R and answer a different experimental question from any E-domain peptide.