Description
PrymaLab · Research Use Only
Sermorelin Peptide 10mg
GHRH 1-29 · the shortest fragment that still works
Sermorelin peptide is the amino-terminal 29 residues of growth hormone releasing hormone, and the interesting fact about it is what was left out. The native hormone is 44 residues. Cutting it back to 29 removed a third of the molecule without removing the activity, which told the field something specific about where receptor binding actually lives.
Specification Table
| Property | Value |
|---|---|
| Compound | Sermorelin |
| Relationship to the native hormone | Residues 1 to 29 of growth hormone releasing hormone, carboxy-terminal amide |
| Residue count | 29 |
| Native hormone residue count | 44 |
| Molecular weight, calculated | Approximately 3,357.9 g/mol for the free base, computed from residue masses plus water |
| CAS, free base | 86168-78-7 |
| CAS, acetate salt | 114466-38-5. Confirm which form a certificate refers to |
| Receptor | GHRHR, the growth hormone releasing hormone receptor, a class B G-protein coupled receptor |
| Principal degradation route in circulation | Dipeptidyl peptidase-4 cleavage after the position 2 alanine |
| Consequence of that route | A short circulating half-life, which later analogues address by substituting position 2 |
| Appearance | White lyophilized powder |
| Purity | Per lot-specific certificate of analysis |
| Solubility | Water soluble. Bacteriostatic water is the usual diluent |
| Storage, lyophilized | 2-8°C short term, -20°C for extended storage, protected from light and moisture |
| Regulatory status | Formerly approved in the United States as Geref and subsequently withdrawn from that market. Material supplied here is not that product |
Why Is Sermorelin Peptide 29 Residues and Not 44?
The truncation is the whole story of this compound and it was an empirical finding rather than a design choice.
Growth hormone releasing hormone was isolated in 1982 from a pancreatic tumour, which is an unusual origin for a hypothalamic peptide and happened because the tumour produced it in quantity large enough to purify.
The native molecule is 44 residues. Once the sequence was known, the obvious next question was which part of it the receptor actually reads.
Systematic truncation answered it. Removing residues from the carboxy terminus made no difference to activity until the chain fell below 29, at which point activity dropped away.
So residues 30 to 44 contribute essentially nothing to receptor activation. They may serve other purposes in the native hormone, and for the purpose of binding GHRHR they are surplus.
That finding is why sermorelin peptide exists as a distinct article. A 29-residue peptide is materially cheaper to synthesise than a 44-residue one and behaves the same at the receptor.
It also localises the pharmacology. Any modification intended to change how the molecule behaves has to happen inside those first 29 residues, because that is where the activity is.
Every later GHRH analogue in this catalogue is built on that conclusion.
One caution about how the truncation finding is usually reported. Equivalent activity was demonstrated in specific assay systems at specific concentrations, not as a universal statement.
Sermorelin peptide and the full-length hormone are equivalent at the receptor in the systems where that was measured. Whether every downstream consequence of receptor activation is identical is a separate question and a smaller literature.
Where Is the Molecule Vulnerable?
Sermorelin peptide has one dominant weakness and it sits two residues from the amino terminus.
Dipeptidyl peptidase-4 is a circulating enzyme that removes dipeptides from the amino end of substrates, and it recognises an alanine or proline at position 2.
Sermorelin carries an alanine there, inherited directly from the native hormone, which makes it a clean substrate.
Cleavage removes the first two residues and the resulting fragment does not activate the receptor, so a single enzymatic step inactivates the molecule.
The published circulating half-life is short as a consequence, measured in minutes rather than hours.
That is not a defect so much as a property of the native sequence, which was never under selective pressure to survive in circulation for long.
The practical consequence for a study design is that sermorelin peptide produces a brief pulse rather than sustained exposure, which happens to resemble the endogenous secretion pattern more closely than a long-acting analogue does.
Whether that is an advantage depends entirely on what the experiment is measuring, and the growth hormone hub sets out why pattern matters as much as amount in this axis.
What Does the Acetate Question Change?
Sermorelin is supplied as a salt and which salt it is changes the arithmetic more than most buyers expect.
Purification by reverse-phase chromatography with trifluoroacetic acid leaves trifluoroacetate paired to every basic site on the molecule. An ion-exchange step can replace that with acetate, and many suppliers do not perform it.
This sequence carries several basic residues, so it carries several counterions, and the two salt forms therefore differ measurably in mass for the same quantity of peptide.
A certificate quoting CAS 86168-78-7 is describing the free base. One quoting 114466-38-5 is describing the acetate. Those are different articles and the number is worth reading rather than skimming.
Net peptide content is the figure that resolves it, stating what fraction of the vial is peptide rather than counterion, water or residual salt.
For a 3,358 dalton peptide the correction is smaller in proportion than it would be for a bioregulator, and it is still commonly fifteen to twenty percent.
Reconstituting a nominal 10 mg vial in 2 mL without that correction gives a figure that is confidently wrong rather than approximately right.
Asking for net peptide content and counterion identity together is one question, and a supplier who answers it has done analysis rather than repackaging.
What Should a Sermorelin Certificate Show?
Six fields cover this compound, and two of them are specific to a peptide of this length.
Purity by reverse-phase HPLC with the detection wavelength stated. This sequence carries tyrosine, so detection at 280 nanometres is possible, and 214 remains the more informative choice because it sees the backbone rather than one residue.
Observed mass against calculated mass, with the instrument resolution stated. At 29 residues a single deletion is roughly three to four percent of total mass, which nominal resolution can miss.
The sequence written out, since a trade name does not distinguish the 1-29 fragment from any other GHRH construct.
Counterion identity and net peptide content, as set out above.
Lot number and synthesis date, without which none of the preceding figures attach to the material in hand.
Whether the carboxy terminus is amidated, because the native fragment is and an unamidated version is a different molecule.
Deletion sequences are the dominant impurity class at this chain length, and they resolve chromatographically more reliably than they resolve by mass, which is why the trace is worth more than the percentage.
A seventh field is worth requesting even though few suppliers volunteer it: the residual solvent figure.
Solid-phase synthesis and lyophilisation both leave traces of organic solvent, and a peptide that has been dried inadequately carries more than one that has not.
It is rarely large enough to matter to a receptor assay and it does matter to the mass balance, because solvent is part of what the balance weighs when the vial is filled.
What Happens Downstream of the Receptor?
GHRHR is a class B G-protein coupled receptor and what it does after binding explains why the pattern of exposure matters as much as the amount.
Activation couples primarily through Gs, raising intracellular cyclic AMP in the somatotroph and activating protein kinase A.
Two things follow from that and they operate on different timescales.
The fast effect is release of growth hormone already stored in secretory granules, which happens within minutes and depends on how much is stored rather than on how much the cell can make.
The slow effect is transcriptional. Protein kinase A activity converges on CREB, which drives expression of the pituitary transcription factor governing somatotroph identity and growth hormone gene transcription.
A stored pool that is released is not immediately replaced, so a second stimulus arriving before the pool refills produces a smaller response than the first.
That is the mechanistic reason a study design has to specify interval as well as concentration, and it is why continuous exposure and pulsed exposure are not interchangeable in this system.
Sermorelin peptide is short-lived by nature, which makes it easier to deliver as a discrete pulse than an analogue engineered to persist.
Whether that is useful depends on what the experiment is asking. A design built to probe pool refill kinetics wants the short-acting compound, and one probing sustained transcriptional response does not.
Neither answer is general and the published literature supports both designs, which is the honest position rather than a hedge.
What Degrades First in Solution?
Two residues in this sequence are chemically reactive once the peptide is in water, and knowing which they are tells a laboratory what to look for.
The methionine near the carboxy end oxidises. Methionine sulfoxide forms readily in the presence of dissolved oxygen, trace metals or light, and it adds sixteen daltons.
That is a small change on a 3,358 dalton molecule, under half a percent, so it sits inside nominal-mass error and is easy to miss on a routine check.
It is not easy to miss chromatographically. Methionine sulfoxide is markedly more polar than methionine, so the oxidised species elutes earlier and separates cleanly on a reverse-phase gradient.
A retention shift toward the void is therefore the first sign that a stored solution has aged, and it appears before any change in the mass spectrum would be convincing.
The second reactive site is the asparagine in the amino-terminal third of the chain. Asparagine deamidates to aspartate, adding one dalton and introducing a negative charge where there was none.
Rate depends heavily on the residue that follows. Asparagine followed by glycine is the fast case, and this sequence has serine there instead, which is slower but not slow.
Deamidation also produces an isoaspartate form alongside the aspartate one, and those two are identical in mass and different in structure.
The practical consequence for sermorelin peptide is that a stored aqueous solution accumulates at least three distinguishable species over weeks, none of which a single mass reading will reliably separate from the parent.
Aliquoting on first reconstitution, excluding light and recording the date is not housekeeping. It is the only control available over a process no routine assay reports.
How Should the Vial Be Handled?
Handling is unremarkable in the dry state and consequential once water is added.
Lyophilized powder sealed against moisture is stable at 2 to 8 degrees Celsius for short periods and at minus 20 for longer, protected from light.
The powder is hygroscopic, so the vial is best brought to room temperature before opening. Condensing atmospheric moisture onto cold powder introduces water that then has to be accounted for.
Reconstitute by adding diluent slowly down the vial wall rather than directly onto the cake, and swirl rather than shake. Vigorous agitation drives aggregation at the air-liquid interface.
In solution the peptide should be aliquoted on first reconstitution rather than returned repeatedly to the freezer, since freeze-thaw cycling is the most avoidable cause of loss.
Adsorption to container walls matters at low working concentrations. Low-binding consumables recover a measurable fraction that ordinary polypropylene does not.
Record the lot, the net peptide content, the diluent volume and the date of first reconstitution. Those four fields let a second laboratory reproduce the preparation.
The date matters most. It is the start of the degradation clock and it is not recoverable afterwards.
Published Literature
Selected references on the discovery of the native hormone and on the fragment.
- Guillemin R, Brazeau P, Bohlen P, Esch F, Ling N, Wehrenberg WB. Science. 1982;218(4572):585-587. DOI: 10.1126/science.6812220
- Prakash A, Goa KL. BioDrugs. 1999;12(2):139-157. DOI: 10.2165/00063030-199912020-00007
- Veldhuis JD, Roemmich JN, Richmond EJ, Rogol AD, Lovejoy JC, Sheffield-Moore M, et al. Endocrine Reviews. 2005;26(1):114-146. DOI: 10.1210/er.2003-0038
- Manning MC, Chou DK, Murphy BM, Payne RW, Katayama DS. Pharmaceutical Research. 2010;27(4):544-575. DOI: 10.1007/s11095-009-0045-6
Frequently Asked Questions
What is sermorelin peptide?
The amino-terminal 29 residues of growth hormone releasing hormone, carrying a carboxy-terminal amide. It binds GHRHR, the same receptor the native 44-residue hormone binds.
Why 29 residues rather than the full 44?
Because systematic truncation showed that removing residues from the carboxy end made no difference to activity until the chain fell below 29. Residues 30 to 44 contribute essentially nothing to receptor activation.
Where did the native hormone come from?
It was isolated in 1982 from a pancreatic tumour that produced it in quantity large enough to purify, which is an unusual origin for a hypothalamic peptide.
What limits its circulating half-life?
Dipeptidyl peptidase-4, which removes dipeptides from the amino end and recognises the alanine at position 2. One enzymatic step removes the first two residues and the fragment no longer activates the receptor.
Do later analogues fix that?
Several do, by substituting position 2 with a residue the enzyme does not recognise. Sermorelin retains the native alanine, so it produces a brief pulse rather than sustained exposure.
Is that a disadvantage?
It depends what is being measured. A brief pulse resembles the endogenous secretion pattern more closely than a long-acting analogue does, and pattern is a variable in this axis rather than a detail.
Which CAS number applies?
86168-78-7 describes the free base and 114466-38-5 the acetate salt. Those are different articles, so the number on a certificate is worth reading rather than skimming.
How large is the counterion correction?
Smaller in proportion than for a short bioregulator, because the molecule is around 3,358 daltons, and still commonly fifteen to twenty percent once water and residual salt are counted.
What detection wavelength should the certificate state?
Either, and it should say which. This sequence carries tyrosine so 280 nanometres works, and 214 is more informative because it detects the peptide backbone rather than a single residue.
What is the dominant impurity at this chain length?
Deletion sequences missing one internal residue. At 29 residues one deletion is roughly three to four percent of total mass, which a nominal-resolution instrument can miss but chromatography separates.
Does it hold an approved formulation?
It was formerly approved in the United States as Geref and later withdrawn from that market. Material supplied here is not that product and is not manufactured to pharmaceutical standards.
How should the vial be stored?
Lyophilized and sealed against moisture at 2 to 8 degrees Celsius short term, minus 20 for longer, protected from light. Bring to room temperature before opening, since the powder is hygroscopic.
Compliance Statement
Sermorelin peptide is sold exclusively for laboratory research use. It is not a drug, food, or cosmetic product, and it is not a dietary product of any kind. It is not approved by the FDA or any comparable authority for human or veterinary use, it was formerly approved in the United States as Geref and subsequently withdrawn from that market, material supplied here is not that product and is not manufactured to pharmaceutical standards, and no compound in this range is offered for any human or veterinary purpose. This product is not intended to diagnose, treat, cure, or prevent any disease. It must not be given to humans or animals. Purchase is restricted to qualified researchers and institutions operating within applicable laws. All handling is the responsibility of the purchasing laboratory.
Other formats of Sermorelin
Sermorelin is also stocked as Sermorelin 6mg preloaded 3ml pen and Sermorelin 5mg. Each listing states its own quantity and concentration, and the pen and vial comparison explains what changes between formats.
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