TB-500: Chemical Profile, Peptide Identity and Quality Testing Overview

Overview

TB-500 is a synthetic peptide material commonly referenced in peptide research and laboratory supply markets. One detail that deserves attention when reviewing TB-500 specifications is that the name is not always used consistently across commercial listings.

In particular, TB-500 may be described as the N-acetylated seven-residue peptide Ac-LKKTETQ, while some suppliers use the name for full-length thymosin beta-4. These are not the same molecular entity and have substantially different molecular weights.

For this reason, the sequence, molecular weight and batch documentation are more useful than the product name alone when reviewing a TB-500 specification.

TB-500 Chemical Identity

For the seven-residue TB-500 peptide recorded in PubChem, the sequence is:

Ac-LKKTETQ-OH

The sequence contains seven amino acid residues:

Leu-Lys-Lys-Thr-Glu-Thr-Gln

The corresponding chemical information is:

These values correspond to the acetylated TB-500 peptide recorded as a distinct chemical entity.

TB-500 and Thymosin Beta-4: Why the Names Can Be Confusing

This is one of the more important points to check when comparing TB-500 products.

Thymosin beta-4 is a much larger 43-amino-acid peptide, while the TB-500 record described above is a seven-residue fragment corresponding to residues 17–23 of thymosin beta-4.

The two materials therefore have very different molecular weights.

This distinction matters when reviewing a specification sheet or analytical report. A molecular mass around 889 Da is consistent with the acetylated seven-residue TB-500 fragment, while a mass around 4,963 Da corresponds to full-length thymosin beta-4.

Reading the TB-500 Sequence

The sequence:

Ac-LKKTETQ-OH

can also be written using the three-letter amino acid notation:

Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln-OH

The Ac- at the beginning represents an N-terminal acetyl group.

That detail is easy to overlook, but it is important when comparing molecular weights or analytical results. The chemical modification is part of the molecular structure and therefore affects the calculated molecular mass.

TB-500 Quality Documentation

A product name by itself provides limited information about the material inside a vial.

For research materials, the more useful information comes from the specification and analytical documentation associated with the particular batch.

Certificate of Analysis

A batch-specific COA may include:

Product name

Batch or lot number

Manufacturing or testing date

Purity result

Identity testing

Analytical method

Laboratory information

The batch number is particularly important because it connects the reported analytical results with a specific production lot.

HPLC Analysis

Reverse-phase HPLC is commonly used when evaluating peptide purity.

An HPLC report may contain:

Chromatogram

Retention time

Area percentage

Analytical conditions

Reported purity

The reported percentage should always be considered together with the analytical method used to obtain it.

A statement such as “≥98% purity” is less informative than a batch-specific report showing how that number was obtained.

Mass Spectrometry

Mass spectrometry provides another important piece of information when reviewing peptide identity.

For the acetylated TB-500 fragment, the expected molecular weight is approximately:

889 Da

An MS result can therefore be compared with the theoretical mass when assessing whether the measured material is consistent with the stated molecular identity.

What to Check When Comparing TB-500 Products

When different suppliers use the same product name, comparing the following fields can help identify inconsistencies:

Sequence

Does the listed sequence correspond to the material being described?

Molecular Weight

Does the stated molecular weight agree with the sequence and chemical form?

CAS Number

Is the CAS number consistent with the specified compound?

Batch Documentation

Does the COA belong to the actual batch being supplied?

Analytical Results

Are HPLC and MS results available for the relevant lot?

These checks are particularly useful for TB-500 because commercial terminology is not always consistent.

A Note About TB-500 Specifications

A specification sheet can contain several technically correct-looking numbers that do not necessarily describe the same molecular entity.

For example, a document might list:

TB-500

CAS: 77591-33-4

MW: 889 Da

That combination deserves further review because the CAS number and molecular weight may refer to different forms or entities.

The safer approach is to compare the sequence + molecular formula + molecular weight + CAS number as a group rather than relying on any single field.

Frequently Asked Questions

What is the molecular weight of TB-500?

For the N-acetylated seven-residue TB-500 peptide Ac-LKKTETQ-OH, the molecular weight is approximately 889.0 g/mol.

What is the sequence of TB-500?

The sequence of the seven-residue TB-500 fragment is:

Ac-LKKTETQ-OH

How many amino acids are in TB-500?

The chemical entity commonly recorded as TB-500 in PubChem contains 7 amino acid residues.

Is TB-500 the same as thymosin beta-4?

They should not be treated as automatically interchangeable. Full-length thymosin beta-4 is a 43-residue peptide, whereas the TB-500 fragment described above is a seven-residue N-acetylated peptide. Their molecular weights and chemical compositions are different.

What documents should be reviewed for a TB-500 research material?

Useful documentation includes a batch-specific COA, HPLC analytical data and mass spectrometry results, together with clear product identity information.

Summary

TB-500 is a good example of why peptide identification should go beyond the product name.

For the N-acetylated heptapeptide form, the key identifiers are:

Sequence: Ac-LKKTETQ-OH

CAS: 885340-08-9

Molecular Formula: C38H68N10O14

Molecular Weight: 889.0 g/mol

When reviewing commercial peptide documentation, sequence, molecular weight, CAS number and batch-specific analytical results should be considered together.

This is especially important for TB-500, where the name is sometimes used inconsistently for the seven-residue fragment and full-length thymosin beta-4.