Sermorelin and modified GRF: the parent and its analogues

The family, in order

Three listings in this category describe closely related 29-residue molecules, and the relationships between them are easy to lose track of. Set out plainly:

Sermorelin is the baseline: the parent hormone's first 29 residues, unaltered. Everything else in the family is that chain with something done to it. See CJC-1295 with and without DAC for the third row.

Why 29 residues was the chosen length

The native hormone is 44 residues, and the published chemistry established that its first 29 carry the receptor-binding activity — the remaining fifteen are not required for it. Truncating at 29 therefore gives a shorter, cheaper synthesis with fewer opportunities for deletion sequences, while retaining the part of the molecule the literature is about. Tesamorelin takes the opposite approach, keeping the full 44 and modifying the end instead.

Reading a report in this family

The complication is that the mass difference between Sermorelin and modified GRF is small — single digits, arising from the substituted residues — which is close enough that it deserves care rather than a glance. Three checks:

• Read the stated molecular formula, not just the mass. For closely related analogues the formula is what makes the number interpretable, and a substitution shows there before it shows in a rounded mass.
• Check which name the report itself uses. A certificate describing Sermorelin and a listing selling modified GRF are not describing the same material, however similar the figures look.
• Expect deletion sequences adjacent to the main peak. At 29 residues these are the dominant impurity class, and their combined size is the informative quantity.

Where identity is reported as HPLC-RTM rather than by mass, the reference standard defines the answer, and for a family this closely spaced the report should name which member that standard was.

Storage of the lyophilized solid

Supplied as a freeze-dried solid, governed by temperature and moisture. Cold storage slows the available chemistry, and the solid is hygroscopic — a vial opened before it has equilibrated to room temperature will draw water out of the air.

Stability is a documented property rather than an assumed one: a laboratory establishes it by holding material under defined conditions and re-analysing at intervals. Where a retest date is stated, the question worth asking is what data supports it. See storing lyophilized research materials.

Scope of this documentation

This page concerns material identification and analytical documentation for laboratory research. It does not recommend personal, human, clinical, therapeutic or veterinary applications. Published research findings do not establish the properties of Arctic stock; use the applicable lot record and its stated methods and limitations.

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