Tirzepatide explained: two receptors, one chain

In this catalogue tirzepatide sits right next to the triple agonist retatrutide and is often compared with it. Chemically, less separates the two than the names suggest. In terms of documentation, a great deal does.

Thirty-nine residues, two receptors

The specification table lists this substance as a GIP/GLP-1 dual agonist, 39 amino acids, fatty-acid modified. In model systems it binds to the GIP and GLP-1 receptors; retatrutide also binds to the glucagon receptor. That is the difference that fits in one sentence, and Retatrutide explained takes it further.

The molecular formula is C₂₂₅H₃₄₈N₄₈O₆₈, the molar mass 4813.45 g/mol and the CAS number 2023788-19-2. Everything is on the product page.

Both have thirty-nine residues, both weigh around four thousand eight hundred grams per mole, and both belong to metabolic research. What follows from this in an organism is a matter of ongoing research and belongs in the scientific literature.

What "fatty-acid modified" means

A fatty acid is attached to the chain. An attachment of this kind binds the molecule to albumin, a protein found in blood plasma, which sets it apart chemically from a bare chain of the same length.

It is the same principle that goes by the abbreviation DAC with CJC-1295, there in a version this catalogue deliberately does not stock. The attachment is part of the molecule: it is included in the molecular formula and the stated mass, and without it this would be a different substance with a different CAS number.

No report in the library

There is currently no certificate of analysis for this substance in the certificate library. The product page therefore shows no lot table and refers to the library instead.

That is the notable difference from its neighbour: retatrutide has four reports, all from the matching vial size. This substance has none. If you need the documented one of the two, you now know which it is, and that is more useful information than any statement about the goods themselves.

What a report would provide for a chain of this length is covered in How to read a certificate of analysis: the method beside the value, the lot number, the date, the laboratory. There is no blanket minimum, and a report without a figure is no substitute for a measured value.

Thirty-eight coupling steps

Thirty-nine residues mean thirty-eight steps in solid-phase synthesis, and in each one a share of the chains stays incomplete. After thirty-eight steps at ninety-nine per cent yield per step, a good two thirds of the target molecule remains. Purification removes the rest, and that largely explains the price gap to short chains on the price list.

Purity should not be confused with peptide content, which is lower because of counterions and residual moisture. It is supplied as a lyophilised powder that goes into solution with bacteriostatic water; the concentration follows from the vial mass and the volume, as described under reconstitution.

In brief

Thirty-nine residues with a fatty-acid attachment, 4813.45 g/mol, CAS 2023788-19-2, and no report in the library. The substance with one more receptor, retatrutide, has four.

Questions

What distinguishes tirzepatide from retatrutide?

The number of receptors: in models tirzepatide binds to GIP and GLP-1, retatrutide additionally to the glucagon receptor. Both have thirty-nine residues and their own CAS numbers.

Is there a certificate of analysis for it?

Not at present. The library holds no report for this substance; for retatrutide it holds four. The product page therefore shows no lot table.

What does fatty-acid modified mean?

That a fatty acid is attached to the chain, which binds the molecule to albumin. The attachment is included in the molecular formula and the stated mass.