Reading a Tesamorelin Certificate of Analysis

Tesamorelin is a 44-residue growth hormone-releasing hormone analogue carrying a trans-3-hexenoyl group on its N-terminus. Both of those facts — the length and the N-terminal modification — change what its certificate looks like and where the useful information sits.

Why length matters for the purity figure

Peptides are built one residue at a time, and each coupling step is slightly less than perfect. The impurities that result are mostly deletion sequences: chains missing a single residue. For a 5-residue peptide there are few opportunities for this; for a 44-residue peptide there are many, and the resulting impurities are chemically very similar to the target.

Two consequences follow:

• Purity figures for long peptides sit lower than for short ones, and a tesamorelin lot in the high 98s is a different achievement from a tripeptide at the same number.
• Deletion sequences co-elute. A chain missing one residue out of 44 behaves almost identically on a reversed-phase column. Some of it will hide under the main peak regardless of how good the method is, which is why the chromatogram’s peak shape matters as much as the percentage. See reading a chromatogram.

The N-terminal modification

The hexenoyl group is what distinguishes tesamorelin from unmodified GHRH analogues. For identity testing this is the thing to check: the measured mass must include the modification. A result matching the bare 44-residue backbone means the material is missing the group that defines the molecule, whatever the purity figure says.

It also makes the molecule somewhat more hydrophobic than the unmodified sequence, so it elutes later in a reversed-phase gradient — useful context when comparing two chromatograms.

Stability considerations visible on a report

Long peptides have more sites at which the common degradation routes can act: asparagine and glutamine residues that can deamidate, methionine that can oxidise, and amide bonds that can hydrolyse. On a certificate this shows up as small satellite peaks close to the main peak, often eluting just before it. Our guide on degradation pathways explains what produces them.

A fresh lot with a clean baseline and one dominant peak is the expectation. A cluster of small neighbours suggests material that has been stored in less than ideal conditions, or a synthesis that was not well purified.

Checks for a tesamorelin lot

1. Content per vial, for how many vials, and how tightly clustered?
2. Purity measured on this lot, with the chromatogram shown rather than just a number?
3. Does the identity result include the N-terminal modification in the expected mass?
4. Does the lot number match the vial, and does the report resolve at the laboratory? See verifying a report.
5. Is the content figure the basis for your calculations, rather than the label weight? See net peptide content.

Our tesamorelin lots

TSM10 and TSM20 each ship against a Janoshik report published with content per vial and HPLC purity exactly as reported, with a link to verify the report at the laboratory. Both appear on their product pages and on the lab results page, in the GHRH and melanocortin analogues class.

Tesamorelin is supplied for laboratory research use only. It is not a medicine and is not for human or veterinary use. This page describes analytical documentation only and makes no claims about biological effects.