Somatropin is a recombinant polypeptide consisting of a single 191-amino-acid chain, matching the primary sequence of the principal circulating form of human growth hormone. It is produced by recombinant DNA technology rather than extracted from pituitary tissue. AminoOptimization Group supplies it as a lyophilised research powder in 12IU and 15IU presentations, tested to 99% HPLC purity, with a Certificate of Analysis available for the lot supplied. This material is offered strictly for laboratory research use. It is not a drug, and it is not for human or veterinary use.
What is somatropin (191aa)?
Somatropin belongs to the growth hormone / prolactin family of single-chain, four-helix-bundle proteins. The 191-residue sequence folds into this characteristic helical bundle, stabilised by two intramolecular disulfide bonds. Recombinant expression in a bacterial host yields a non-glycosylated protein, which is the basis for the “191aa” designation used in the literature to distinguish this form from a 192-residue variant carrying an additional N-terminal methionine, an artifact of some earlier expression constructs.
Because the 191-amino-acid sequence corresponds to the endogenous protein without that extra methionine residue, it is the form most frequently used as a reference standard in structural and receptor-binding studies of growth hormone pharmacology. Analytical characterisation of material in this class typically includes reversed-phase HPLC for purity, alongside methods such as mass spectrometry and isoelectric focusing to confirm identity and to detect deamidation or aggregation, both recognised degradation pathways for this molecule.
Specifications
- Compound: Somatropin (HGH, 191aa)
- CAS number: 12629-01-5
- Molecular formula: C990H1529N263O299S7
- Molecular weight: 22,124 Da
- Purity: 99% HPLC
- Presentation: Lyophilised powder, sealed vial
- Available sizes: 12IU / 15IU
- Physical form: White to off-white powder
- Classification: Research peptide — not for human or veterinary use
Research context
Growth hormone receptor pharmacology is a substantial area of published research. Studies in cell-based and animal model systems examine how ligand binding drives sequential engagement of two distinct sites on the growth hormone receptor, producing a 1:2 hormone–receptor complex and receptor dimerisation. This dimerisation event is studied as the trigger for downstream JAK2 tyrosine kinase activation and STAT5 signalling.
Recombinant 191-amino-acid material is also used in comparative analytical work — for example, studies comparing receptor-binding affinity, thermal stability, or immunogenic potential across different recombinant expression systems and formulations.
None of this literature establishes safety or efficacy for use in humans. It is provided as research context only.
Reconstitution
Lyophilised protein requires reconstitution with a suitable sterile diluent before use in solution. Bacteriostatic water is the diluent most commonly specified for multi-use laboratory preparations; sterile water is typical for single-use work.
Direct the diluent stream against the inner wall of the vial rather than onto the powder itself, and allow the material to dissolve without agitation. Proteins of this size are susceptible to shear stress and to foaming — do not shake the vial. Swirl gently if needed, and allow several minutes at room temperature for complete dissolution.
Working concentration is a function of how much diluent is added to a given vial. Our peptide reconstitution calculator computes the resulting concentration for any combination of vial size and diluent volume.
Storage and stability
Before reconstitution: store the sealed vial in a freezer at -20 °C, protected from light. Lyophilised material in this class is comparatively stable in this state. Brief excursions to ambient temperature during shipping are normal and are not expected to compromise a properly lyophilised product.
After reconstitution: refrigerate at 2–8 °C and protect from light. Material in solution is materially less stable than the dry powder. Avoid repeated freeze-thaw cycles, a well-documented cause of aggregation and loss of measurable activity in proteins of this size — aliquot instead if repeated sampling is required.
Inspect solutions before use. Cloudiness, visible particulate, or discolouration indicate the material should not be relied upon for quantitative work.
Certificate of Analysis
Every lot is tested by high-performance liquid chromatography, and the purity figure shown above refers to analytical results for the specific lot supplied — not to a generic specification. A Certificate of Analysis is available on request, and we will provide lot-specific documentation before purchase if your protocol requires it.
Purity by HPLC describes the proportion of the target protein relative to detectable related substances. It is a statement about the material as manufactured and tested. It is expressly not a representation that the material is suitable for any use in humans or animals.
Handling and safety
Handle in accordance with good laboratory practice. Use appropriate personal protective equipment, work in a suitable containment environment, and dispose of material and consumables according to your institution’s requirements and applicable local regulation. Anyone with access to this material should understand that it is not for human or veterinary use.
Frequently asked questions
What does the “191aa” designation mean?
It refers to the 191-amino-acid sequence of this form of recombinant somatropin, which lacks the additional N-terminal methionine present in some earlier recombinant constructs. It is the form most commonly used as a reference standard in receptor-binding and structural studies.
Is somatropin approved in Canada?
Recombinant human growth hormone is an active ingredient in a small number of prescription drug products authorised by Health Canada for specific, physician-diagnosed medical conditions. This is not one of those products. It has not been evaluated by Health Canada, the FDA, or any comparable regulatory authority, is not manufactured under a Health Canada drug licence, and carries no Drug Identification Number (DIN) or Natural Product Number (NPN). It is supplied exclusively for laboratory research and is not authorised for any human or veterinary use.
How much diluent should be used?
That depends on the working concentration your protocol requires. Use the reconstitution calculator to work out the resulting concentration for your vial size.
How long is reconstituted material usable?
Stability in solution is shorter than in lyophilised form and depends on diluent, temperature, and handling. Refrigerate at 2–8 °C, protect from light, avoid freeze-thaw cycling, and validate stability for your own storage conditions if your work depends on it.
Do you provide a Certificate of Analysis?
Yes — lot-specific, available on request, including before purchase.
Research use only
This product is supplied solely for laboratory and scientific research. It is not a drug, food, cosmetic, or medical device, and it must not be administered to humans or animals. Nothing on this page is medical advice or a therapeutic claim. Full terms are set out in our Research Use Only Disclaimer.
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