Research

Semaglutide Explained: Structure, Mass and How to Verify a Batch

3 min read · Research blog · 12 Nov 2026 · By CellMind Research Team

Semaglutide is a synthetic analogue of the hormone GLP-1 with 31 amino acids. Two changes set it apart from natural GLP-1: an Aib residue at position 2 and a C18 fatty diacid attached to a lysine. Its molecular mass is about 4,113.6 Da. This guide explains its structure, what the literature covers and how to verify a batch.

Key facts

Type: Synthetic 31-amino-acid analogue of human GLP-1; GLP-1 receptor agonist
Sequence: GLP-1(7–37) with Aib at position 8, arginine at position 34 and a C18 fatty diacid on lysine 26
Molecular formula: C187H291N45O59
Molecular mass: about 4,113.6 Da
CAS number: 910463-68-2
Supplied as: lyophilised powder in a sealed vial

What is semaglutide

Semaglutide keeps most of the sequence of human GLP-1. Alanine at position 8 is replaced by α-aminoisobutyric acid (Aib), which protects the peptide from the enzyme DPP-4. Lysine at position 34 is replaced by arginine, so that the fatty side chain attaches only to lysine 26. That side chain ends in an 18-carbon diacid and lets the peptide bind to albumin.

What the scientific literature covers

The compound was first described in 2015. Published work spans cell assays, animal models and clinical trials. Laboratory topics include:

GLP-1 receptor binding and cAMP signalling in cell assays
Resistance to the enzyme DPP-4 through the Aib substitution
Albumin binding of the C18 side chain
Glucose regulation in rodent models

These are laboratory findings. CellMind supplies Semaglutide for research purposes only, not for human use. Semaglutide is also the active substance of an approved medicine. CellMind material is a research compound, not a medicine.

How identity and purity are verified

Semaglutide is a lipidated peptide: it elutes late on reversed-phase HPLC and can form aggregates in solution. HPLC separates the target peptide from shortened sequences and oxidised forms. Mass spectrometry confirms the mass of about 4,113.6 Da, which tells it apart from liraglutide (about 3,751.2 Da), a related GLP-1 analogue. Both results must appear on the certificate of analysis (CoA) for the specific batch. Our CoA guide explains how to read one.

Checklist before buying Semaglutide

A CoA for the specific batch
HPLC purity stated as a number, above 99%
Mass of about 4,113.6 Da confirmed on the report
A clearly stated amount per vial (10 mg)
A batch number on the vial that matches the report

Common questions about Semaglutide

How is semaglutide different from liraglutide?

Both are analogues of GLP-1 with a fatty side chain. Semaglutide has an Aib residue at position 8 and a C18 fatty diacid; liraglutide keeps alanine at position 8 and carries a C16 fatty acid. Their masses differ: about 4,113.6 Da against about 3,751.2 Da.

What mass should a semaglutide report show?

About 4,113.6 Da. Salt forms weigh more, so the report should state which form was measured.

Is research semaglutide the same as the medicine?

No. An approved medicine is a finished, regulated product. Research material is a reference compound for laboratory work and is not for human use.

Storage and handling

Keep lyophilised vials in a cool, dark place. After reconstitution the solution should be refrigerated and used within the planned study period. Avoid repeated temperature changes: they are the most common cause of degradation that nobody notices until results stop matching.