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Molecular Weight
Purity
Storage
Appearance
Solubility
01
Thymosin Alpha-1 (Tα1, international non-proprietary name thymalfasin) is a 28-residue polypeptide with an acetylated N-terminus. It was first isolated from a calf thymus extract known as thymosin fraction 5 and is now produced by chemical synthesis.
It is strongly acidic, has no cysteines and no aromatic residues, and has been studied mainly for its effects on immune cells such as dendritic cells and T lymphocytes. Thymalfasin is also the active ingredient of a medicine approved in some countries; the material listed here is supplied solely as a lyophilized reference compound for in vitro and analytical research.
02
Thymosin Alpha-1 is a flexible, highly acidic polypeptide.
Sequence
Ac-Ser-Asp-Ala-Ala-Val-Asp-Thr-Ser-Ser-Glu-Ile-Thr-Thr-Lys-Asp-Leu-Lys-Glu-Lys-Lys-Glu-Val-Val-Glu-Glu-Ala-Glu-Asn-OH.
Charge
It contains six glutamates and three aspartates against four lysines. With the N-terminus acetylated and the C-terminus free, the net charge is about −6 at neutral pH and the isoelectric point is low (around 4).
N-terminal acetyl group
Acetylation of Ser1 matches the natural peptide, adds 42.01 Da and blocks aminopeptidases. The non-acetylated form is a common synthesis impurity.
Asn28
The C-terminal asparagine can deamidate (+0.98 Da) to aspartate or isoaspartate, the main chemical degradation route.
Structure
There is no cysteine, tryptophan or tyrosine. In water the peptide is largely unstructured, with some helical tendency in its central-to-C-terminal region.
Not related to thymosin β4
Despite the shared name, thymosin α1 and thymosin β4 (TB-500) are unrelated peptides with different sequences, structures and functions.
03
Research on Thymosin Alpha-1 centres on immune signalling.
Dendritic cells
In vitro studies reported changes in maturation markers, such as MHC class II and co-stimulatory molecules, on dendritic cells after exposure.
Cytokine responses
Experiments in peripheral blood mononuclear cell cultures measured changes in interleukin and interferon expression.
Toll-like receptor signalling
Published work proposes that Thymosin Alpha-1 acts through Toll-like receptors, particularly TLR9, and the MyD88–NF-κB pathway. This remains an area of active investigation.
These findings are cited as research context only; no effects are claimed for this material.
04
Immune-cell assays
A reference compound in dendritic cell, T-cell and cytokine assays.
Charge-variant analysis
Its strong negative charge makes it a useful test analyte for ion-exchange chromatography and capillary electrophoresis, including separation of deamidated variants.
N-terminal acetylation analysis
A positive control for confirming N-terminal acetylation by MS/MS and for distinguishing acetylation (42.011 Da) from trimethylation (42.047 Da) by high-resolution MS.
Deamidation studies
A model substrate for measuring Asn deamidation rates under different pH and temperature conditions.
05
Storage
Store the lyophilized powder at −20 °C, sealed and desiccated.
Reconstitution
Dissolves readily in water or near-neutral buffer. Swirl gently; vigorous vortexing can cause foaming and surface losses.
Deamidation
Asn28 deamidation is faster above pH 8, at higher temperatures and over long periods in solution. Slightly acidic buffers (around pH 5–6) slow it. Use solutions promptly or freeze aliquots.
Other pathways
The peptide also contains three aspartates, which can isomerise slowly, fastest at mildly acidic pH. There is no methionine, cysteine or tryptophan, so oxidation is not a concern.
Labware
Use low-binding polypropylene tubes and avoid repeated freeze–thaw cycles.
06
Analysis must confirm the sequence, the N-terminal acetyl group and the deamidation level.
HPLC
Reversed-phase C18 with a 0.1% TFA gradient gives a well-defined peak. Detect at 214 nm, since there are no aromatic residues. Deamidated forms elute close to the main peak and need an optimised gradient, or ion-exchange chromatography, for full resolution.
Mass spectrometry
ESI gives a series of multiply charged ions. The [M+3H]³⁺ ion appears at about m/z 1036.5 (monoisotopic; about 1037.1 by average mass). Acidic peptides like this also ionise well in negative mode.
Acetylation check
The non-acetylated impurity is 42 Da lighter, which appears as a 14 m/z spacing at the 3+ charge state. High-resolution MS distinguishes acetylation from trimethylation, and N-terminal Edman sequencing gives no signal from the first cycle when the acetyl group is present.
Impurity profile
Typical checks include the non-acetylated form, Asn28 deamidation products (+0.98 Da), isoAsp variants, deletion and truncated sequences, and counter-ion content.
07
It is a single, fully defined 28-residue peptide with an acetylated N-terminus, made synthetically. Thymus extracts such as thymosin fraction 5 or Thymalin are mixtures of many components. It is also unrelated to thymosin β4 (TB-500) despite the similar name.
It is part of the native structure, and the non-acetylated form is a common synthesis impurity. Its presence must be confirmed by mass (+42.01 Da), distinguished from trimethylation by high-resolution MS, and can be checked by the absence of an Edman signal from the first residue.
Deamidation adds about 1 Da and introduces an extra negative charge. It is measured by optimised reversed-phase HPLC, by ion-exchange chromatography or capillary electrophoresis (which separate the charge variants), and confirmed by high-resolution LC-MS.
It gives a series of multiply charged ions, with the 3+ ion at about m/z 1036.5 (monoisotopic). As a strongly acidic peptide, it also gives good signals in negative-ion mode.
Identity by accurate mass and MS/MS, HPLC purity, the level of the non-acetylated form, Asn28 deamidation and isoAsp content, peptide content and counter-ion content, all compared with the certificate of analysis.
No. Although thymalfasin is used in medicines in some countries, the material listed here is supplied strictly as a reference compound for laboratory and analytical research and is not for human or animal use.
Thymosin Alpha-1 Research Reference. (2026). Pure Peptides Labs Research Catalogue. Retrieved from https://purepeptideslabs.net/research-catalogue/cellular-research-peptides/thymosin-alpha-1/
Materials listed on this platform are supported by independent testing and published documentation for laboratory research contexts.
