Retatrutide explained: 39 residues, three receptors

Retatrutide is the longest molecule in this catalogue and the one most often searched for. This article gathers the documented facts: chain length, mass, identification number and the four analytical reports held in the library.

Three receptors instead of one

In metabolic research retatrutide is classed as a triple agonist: in model systems it binds to the GIP, GLP-1 and glucagon receptors. That is the difference from tirzepatide, which binds two of the three in the same models. Nothing more can be summarised responsibly in one sentence; the rest is set out in Tirzepatide explained.

What follows from this in an organism is a matter of ongoing research and belongs in the scientific literature, not on the page of a chemicals supplier. What you will find here are the details from the specification table.

39 amino acids, 4731.42 g/mol

The sequence comprises 39 amino acids. The molecular formula is C₂₂₁H₃₄₂N₄₆O₆₈, the molar mass is 4731.42 g/mol and the CAS number is 2381089-83-2. All four details are on the product page.

For comparison: GHK-Cu comes to 403.93 g/mol and Semax to 813.92. Retatrutide is therefore roughly ten times as heavy as the short regulatory peptides in this catalogue.

Why length ends up in the price

39 residues mean 38 coupling steps in solid-phase synthesis. Each one is an opportunity for an incomplete coupling. Assuming a yield of ninety-nine per cent per step, a good two thirds of the target molecule remains after 38 steps; the rest has to be separated out.

That separation is the real effort. It largely explains the gap to the short chains on the price list: not margin, but synthesis steps.

Four reports, all above 99.8%

The certificate library holds four analytical reports for this substance. All four come from 10 mg lots, the same fill size sold here. That is the case for this substance, but not for several others.

All four give a measured purity of above 99.8%. This shop states no blanket minimum purity; what counts is the measured value in the report for each lot. For a chain of this length that is notable and worth a look at the certificate itself: the method, lot number, date and laboratory are listed there beside the value.

A value such as "above 99.8%" is not rounding up, by the way, but the detection limit of the method: above it, HPLC can no longer tell whether any residue remains.

Purity is not peptide content

The two are regularly confused. Purity states what share of the detected area in the chromatogram belongs to the target substance. Peptide content states what share of the weighed material is pure peptide, and because of counterions and residual moisture it is regularly lower. A vial with 99.8% purity does not contain 99.8% peptide.

What this means for the weighed mass is covered in detail in What is really in the vial.

Before reconstitution

It is supplied as a lyophilised powder. It goes into solution with bacteriostatic water; the concentration follows from the vial mass and the volume, as described under reconstitution.

In brief

39 amino acids, 4731.42 g/mol, CAS 2381089-83-2, four analytical reports from the matching vial size, all above 99.8%. Its two-receptor neighbour, documented very differently, is covered in Tirzepatide explained.

Questions

How do retatrutide and tirzepatide differ?

In the number of receptors they bind to in model systems: GIP and GLP-1 for tirzepatide, and additionally the glucagon receptor for retatrutide. Each has its own CAS number, and every analytical report belongs to one lot of one substance.

How heavy is the molecule?

4731.42 g/mol with 39 amino acids. That makes it the longest molecule in this catalogue; the short regulatory peptides weigh around a tenth of that.

How many analytical reports are there?

Four, all from 10 mg lots and all with a measured purity above 99.8%. They can be viewed in the certificate library without an account.