Tesamorelin is a nonproprietary name for a modified peptide, not a systematic chemical name. What follows is an identity reference for Tesamorelin: what the sequence is, what the N-terminal modification looks like, what mass to expect, how a peptide of this length behaves under reverse-phase HPLC, and how a buyer can confirm that the material in a vial is what the label says. It leaves aside any question of what Tesamorelin does, and it contains no guidance on preparation, handling or dosing.
The sequence behind Tesamorelin
Tesamorelin is the full 44-residue sequence of human growth hormone-releasing hormone, GHRH(1–44), with a C-terminal amide and one synthetic addition: a trans-3-hexenoyl group acylated onto the N-terminal tyrosine. Written out:
trans-3-hexenoyl-Tyr-Ala-Asp-Ala-Ile-Phe-Thr-Asn-Ser-Tyr-Arg-Lys-Val-Leu-Gly-Gln-Leu-Ser-Ala-Arg-Lys-Leu-Leu-Gln-Asp-Ile-Met-Ser-Arg-Gln-Gln-Gly-Glu-Ser-Asn-Gln-Glu-Arg-Gly-Ala-Arg-Ala-Arg-Leu-NH2
In one-letter code the peptide chain is YADAIFTNSYRKVLGQLSARKLLQDIMSRQQGESNQERGARARL-NH2. Apart from the hexenoyl cap, every residue is a standard L-amino acid. The molecular formula is C221H366N72O67S and the average molecular mass is approximately 5136 g/mol. The single sulfur atom in that formula belongs to the methionine at position 27.
The hexenoyl group is a six-carbon acyl chain with one carbon–carbon double bond in the trans configuration. It replaces a hydrogen on the N-terminal amine, so the peptide has no free N-terminus: the amine that would normally be available is part of an amide bond to the acyl chain.
What the name Tesamorelin refers to
Tesamorelin sits in a small group of research compounds built on the GHRH sequence, and the members differ in ways a name does not make obvious. Sermorelin is the first 29 residues of GHRH with a C-terminal amide and no N-terminal modification. The compounds discussed in CJC-1295 vs CJC-1295 DAC are 29-residue analogues with several amino acid substitutions. Tesamorelin keeps all 44 native residues and changes only the N-terminus.
That makes mass the quickest discriminator. A 29-residue GHRH analogue weighs in the low thousands; tesamorelin sits above 5,000. An unmodified GHRH(1–44) amide would weigh less than tesamorelin by the mass of the hexenoyl group, roughly 96 daltons. A certificate that reports the right order of magnitude but the wrong fine mass is describing a different molecule.
How tesamorelin behaves on reverse-phase HPLC
At 44 residues, tesamorelin is a long peptide by synthetic standards, and it behaves like one. It carries many basic residues — arginines and lysines spread along the chain — balanced by aspartates and glutamates, plus a hydrophobic core of leucines, isoleucines, a valine and a phenylalanine. The hexenoyl cap adds further hydrophobic character at the N-terminus. On a C18 or C4 column with a water/acetonitrile gradient and trifluoroacetic acid, it retains strongly and elutes well into the gradient, later than the unacylated sequence would.
Tesamorelin contains two tyrosines and one phenylalanine but no tryptophan, so its absorbance at 280 nm is modest. Purity is read at around 214 nm, where every peptide bond absorbs and where a 44-residue chain gives a strong signal.
Length brings impurity questions that short peptides do not have. Each coupling step in a solid-phase synthesis is a chance for a deletion sequence, and a 44-residue synthesis has many such steps; single-residue deletions of a long peptide can elute very close to the main peak. The methionine at position 27 can oxidise to the sulfoxide, which adds 16 daltons and usually elutes slightly earlier. Species lacking the hexenoyl group, or carrying the cis rather than the trans double bond, are further possibilities a well-resolved method should be able to separate. Our guide to reading an HPLC chromatogram covers how shoulders and closely eluting peaks show up.
What an analysis for tesamorelin should show
A useful certificate reports the column chemistry and dimensions, the mobile phase and gradient, the detection wavelength, the retention time, the integrated peak area with the integration window visible, and a mass confirmation. For a peptide of this size, electrospray mass spectra usually show a series of multiply charged ions rather than a single peak; the deconvoluted mass should land at approximately 5136.
Expect the Tesamorelin report to give net peptide content as a separate number from HPLC purity, and to name the counter-ion. With a large number of basic side chains, a 44-residue peptide can carry many counter-ions per molecule, so the salt form still matters even at this mass. Chromatographic purity describes the peptide fraction; net peptide content describes how much of the powder is peptide at all.
Confirming identity independently
Search on the structure, not the designation. Public chemical databases index tesamorelin by formula and by full structure, including the hexenoyl group, and a search on C221H366N72O67S will show whether the pairing of name and structure a vendor uses matches the pairing used elsewhere. Then check two things on the published analysis: that the deconvoluted mass sits near 5136 rather than near an unmodified GHRH mass, and that the purity method is capable of separating closely related long-chain impurities.
How tesamorelin is supplied here
Tesamorelin 10mg and Tesamorelin 5mg are each supplied as a lyophilised powder in a sealed vial. Independent reverse-phase HPLC is run on Tesamorelin, and the result sits on the product page. Vial size and HPLC purity for Tesamorelin are both stated on its product page. A Tesamorelin vial has no batch or lot marking, so the crimp and cap color are what tie it to the published result.
Frequently asked questions
What is the sequence of tesamorelin?
The 44 residues of human GHRH, YADAIFTNSYRKVLGQLSARKLLQDIMSRQQGESNQERGARARL-NH2, with a trans-3-hexenoyl group on the N-terminal tyrosine.
Is tesamorelin the same as sermorelin?
No. Sermorelin is GHRH(1–29) amide with a free N-terminus. Tesamorelin is the full 44-residue sequence with an N-terminal hexenoyl group. They differ substantially in length and mass.
What molecular weight should I expect for Tesamorelin?
Approximately 5136 g/mol, formula C221H366N72O67S. Any counter-ion adds to the weighed mass of Tesamorelin, so it should be declared with the figure.
Why does the mass spectrum show several peaks?
Large peptides pick up several protons during electrospray ionisation and appear as a ladder of charge states. Deconvolution converts that ladder into a single neutral mass for comparison with the expected value.
Research use only. All products supplied by Battle Born Peptides are laboratory reference materials for in-vitro research and analytical use by qualified professionals. They are not drugs, foods, dietary supplements, cosmetics or medical devices; they are not approved by the FDA or any other regulator for use in humans or animals; and they are not intended to diagnose, treat, cure, mitigate or prevent any disease, or to affect the structure or any function of the body of humans or animals. Nothing in this article is preparation, handling or dosing guidance. See our full research-use terms.