Sermorelin: structure and analysis

What is Sermorelin?

Sermorelin is the first 29 amino acids of growth hormone-releasing hormone, produced synthetically as the C-terminal amide. It is the native fragment rather than an analog: no substitutions, no acyl modification, no drug-affinity complex.

Growth hormone-releasing hormone is a 44-residue peptide, and the 1-29 fragment retains the activity of the full sequence — which is why three compounds in this catalogue are built on it.

The C-terminal amide is the one deliberate departure from the plain fragment, and it is a structural feature rather than an incidental one.

How is Sermorelin produced?

Assembled by solid-phase peptide synthesis: the chain is built one residue at a time on an insoluble resin support, then cleaved from the resin, deprotected and purified — most commonly by reversed-phase high-performance liquid chromatography. The purified material is lyophilized to a dry solid.

The impurity profile that appears on a certificate is a record of where that process was imperfect: deletion sequences from an incomplete coupling, truncated chains, and species retaining a protecting group.

What are the molecular figures for Sermorelin?

Calculated from the formula C149H246N44O42S, not measured. The average molecular weight counts the natural abundance of each element's isotopes; the monoisotopic mass is the mass of the single most abundant isotopic composition, which is the figure a mass spectrometer is usually compared against.

Two masses describe this molecule and they are not the same number. The monoisotopic mass assumes every carbon is carbon-12; the tallest peak in the isotope envelope sits 1 carbon-13 substitution above it, because for a molecule with 149 carbons that is the most probable composition. A specification or a database quoting the higher figure is not necessarily wrong — it is quoting the other peak, and both are given here.

Adducts, salts, modifications and multiply charged species all move an observed m/z away from any figure calculated here, and a certificate reports what was measured for a batch rather than what was expected of it.

What is the sequence of Sermorelin?

Sermorelin is 29 residues long. Written in the one-letter amino-acid code, as the cited record states it:

The sequence is what an identity test resolves. The mass a spectrometer is compared against is the mass this chain implies, which is why a single missing or substituted residue changes the result by an amount that cannot be mistaken for instrument variation — the deletion is detectable rather than invisible.

Sequence information describes the molecule, not the material in a vial. What establishes a specific batch is the identity method and result on its certificate.

How does Sermorelin compare with related compounds?

Related compounds are not interchangeable. Published figures differ between them, and in this catalogue three compounds share a GHRH backbone while several share the same structural class — which is exactly why identity is confirmed analytically rather than inferred from the label.

How is the identity of Sermorelin confirmed?

Mass spectrometry confirms the 29-residue chain and the C-terminal amide. The amide and the corresponding free acid differ by approximately one mass unit, so distinguishing them requires high-resolution measurement — and they are different compounds.

Because this is the unmodified fragment, its mass also distinguishes it from CJC-1295 without DAC, which is the same fragment carrying four substitutions.

Which impurities can appear in Sermorelin?

Twenty-nine residues means twenty-nine coupling steps, and the probability of at least one incomplete coupling rises with chain length. Deletion sequences differing from the target by a single residue are the expected impurity class, and they are closely spaced chromatographically.

Incomplete C-terminal amidation is the other characteristic impurity, and the small mass shift involved makes it a result that depends on the resolution of the identity method.

With three GHRH-derived compounds in this catalogue, the identity result is what establishes which is in a given vial. Their masses differ and they are not interchangeable.

What does a certificate of analysis for Sermorelin report?

A certificate for a batch of this material names the batch, names the issuing laboratory, and states for each parameter both the method used and the specification the result was measured against. Identity and purity are the two core results; net peptide content states how much of the fill weight is actually peptide.

A certificate belongs to a batch, not to a product line. When a new batch is released it is tested again, and the certificate published against it is that batch's certificate — a previous batch's result is never carried forward.

Is Sermorelin for human use?

No. This page describes structure and analysis. It makes no claim about what this compound does, and none should be inferred from it. Material is supplied for laboratory research use only: it is not a drug, food, dietary supplement, cosmetic or medical device, it is not for human or veterinary consumption, and no dosing, administration or reconstitution guidance is provided for any such use.

References

• Sermorelin — PubChem, National Library of Medicine
• Somatoliberin (GHRH) — human — UniProt Knowledgebase
• Sermorelin Acetate — ChEMBL, European Bioinformatics Institute