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:
| Listing | What it is | Approximate mass |
|---|---|---|
| Sermorelin | GHRH residues 1-29, unmodified | near 3,358 g/mol |
| Modified GRF (1-29) | Same 29 residues with stabilising substitutions | near 3,367 g/mol |
| CJC-1295 with DAC | Modified chain plus a maleimidoproprionyl linker | near 3,650 g/mol |
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.
What the published literature covers
The research record on growth-hormone-releasing hormone and its truncated analogues is long-standing and largely preclinical, covering receptor pharmacology, structure-activity work establishing which residues matter, and animal models. Because the family members differ in how quickly they are broken down rather than in what they bind, much of the comparative literature is about stability rather than activity.
The compound has not completed the regulatory process that would establish safety or efficacy for any medical indication, and findings in animal models and cell culture do not transfer automatically to other species. Arctic Lab Supply does not publish research conclusions, recommend applications, or provide guidance on experimental design.