Key findings
- The original characterisation separated the peptide from a thymic polypeptide fraction and determined its sequence, describing a heat stable, highly acidic molecule of 28 amino acid residues and one of several peptides present in that fraction. [1]
- Solution NMR at 800 MHz in aqueous trifluoroethanol resolved two stable regions: an alpha-helix from residue 14 to residue 26 and two double beta-turns forming a distorted helical structure in the N-terminal twelve residues. [2]
- The natural form carries an N-terminal acetyl group, and the cited synthesis work describes both the chemical difficulty of assembling the 28-residue acetylated peptide and an enzymatic route to installing that acetyl group. [3][4]
- In human dendritic cell cultures the direction of the response depended on the stimulus: maturation markers and cytokines rose with viral TLR3 and TLR7/8 agonists and with an influenza A infection, and fell after bacterial TLR2 and TLR4 stimulation. [5][6]
Identity and structure
- Length and character
- A heat stable, highly acidic polypeptide of 28 amino acid residues whose sequence was determined in the cited isolation work [1]
- Origin
- Isolated from calf thymus as one of several polypeptides present in the fraction the same authors named thymosin fraction 5 [1]
- N-terminal modification
- The natural form is N-alpha-acetylated, which the cited work links to stability of the peptide; a synthetic lot without that acetyl group is a different material [4][3]
- Solution conformation
- An alpha-helix spanning residues 14 to 26 with two double beta-turns across the N-terminal twelve residues, resolved in 40 percent trifluoroethanol and 60 percent water [2]
- Form as supplied
- Sterile lyophilized powder
Mechanism as studied
The cited immunology work places the peptide upstream of dendritic cell maturation rather than at a named receptor of its own. Fungus-pulsed dendritic cells matured and produced interleukin 12 through a p38 MAP kinase and NF-kappaB dependent pathway, and that signalling ran through the myeloid differentiation factor 88 adaptor and distinct Toll-like receptors. [6]
A second dendritic cell study makes the stimulus dependence explicit. With viral TLR3 and TLR7/8 agonists the peptide raised HLA class I and class II surface expression and secretion of IL-6, TNF-alpha and IL-8, and raised maturation markers and type I and type III interferon in influenza A infected cells. After bacterial TLR2 and TLR4 stimulation or mycobacterial infection the same measurements fell sharply. [5]
Transcriptional and cell surface readouts describe the breadth rather than a pathway. Profiling 8300 genes in human peripheral blood mononuclear cells found a number of genes not previously reported as modulated by this peptide, and work on isolated CD8 positive T cells found activation markers and cytokines rose most when the peptide accompanied CD3 and CD28 stimulation rather than acting alone. [7][8]
Research findings
Analytical
- System
- A biologically active polypeptide isolated from calf thymus, separated from the thymosin fraction 5 mixture
- Measured
- Amino acid sequence of the isolated polypeptide, its residue count, its heat stability and its acidity
- Reported
- The sequence was determined for a heat stable, highly acidic molecule composed of 28 amino acid residues, described as one of several peptides present in thymosin fraction 5, and a nomenclature for that family of polypeptides was proposed. [1]
Structural
- System
- The 28-residue peptide in 40 percent trifluoroethanol and 60 percent water
- Measured
- Solution structure by 800 MHz NMR with restrained molecular dynamics in an explicit solvent box of the same composition
- Reported
- The peptide adopted a structured conformation with two stable regions: an alpha-helix from residue 14 to residue 26, and two double beta-turns across the N-terminal twelve residues forming a distorted helical structure. [2]
Analytical
- System
- Two 14-residue segments made by solid phase synthesis and joined in water by an engineered thiol-subtilisin ligase, with the enzyme crystallised
- Measured
- Yield of the segment condensation, the crystal structure of the engineered ligase against the model used for the engineering, and the overall yield of the combined route on a gram scale
- Reported
- The authors describe conventional chemical synthesis of the acetylated 28-residue peptide as exceptionally challenging. The tailored ligase joined the two segments at above 94 percent yield, its crystal structure agreed with the engineering model, and the combined route gave a 55 percent overall yield, twice that typical of existing processes. [3]
Analytical
- System
- A fusion of the peptide with human serum albumin expressed in Pichia pastoris, rather than the free peptide, acetylated in vitro by a purified bacterial N-alpha-acetyltransferase
- Measured
- N-alpha-acetylation of the fusion protein by LC-MS/MS, enzyme affinity for the desacetyl peptide against the fusion, and retained bioactivity by assay
- Reported
- Incubation with the acetyltransferase and acetyl coenzyme A produced the N-alpha-acetylated fusion, confirmed by mass spectrometry. The enzyme had higher affinity for the free desacetyl peptide than for the fusion, and activity was fully retained when the peptide sat at the N-terminus of the fusion but was reduced in the reversed arrangement. [4]
In vitro
- System
- Dendritic cells pulsed with Aspergillus fumigatus, with a mouse model reported alongside
- Measured
- Functional maturation of the dendritic cells, interleukin 12 production, involvement of the p38 MAP kinase and NF-kappaB pathway, and the requirement for the myeloid differentiation factor 88 adaptor and for distinct Toll-like receptors
- Reported
- The peptide induced functional maturation and interleukin 12 production by the fungus-pulsed cells through a p38 MAP kinase and NF-kappaB dependent pathway, and the signal ran through the myeloid differentiation factor 88 dependent pathway involving distinct Toll-like receptors. [6]
In vitro
- System
- Human primary monocyte-derived dendritic cells exposed to viral or bacterial Toll-like receptor agonists, to pandemic H1N1 influenza A, or to Bacillus Calmette-Guerin
- Measured
- Dendritic cell maturation markers, HLA class I and class II surface expression, secretion of IL-6, TNF-alpha and IL-8, and type I and type III interferon expression
- Reported
- With viral TLR3 and TLR7/8 agonists the peptide raised HLA class I and II surface expression and IL-6, TNF-alpha and IL-8 secretion, and in influenza A infected cells it raised maturation markers and type I and III interferon. Following bacterial TLR2 and TLR4 stimulation and after Bacillus Calmette-Guerin infection the same parameters were drastically lowered. [5]
In vitro
- System
- Human peripheral blood mononuclear cells exposed to the peptide in culture
- Measured
- Transcription profile across 8300 genes
- Reported
- Alongside genes already known to be modulated by the peptide, the analysis found a number of genes not previously described as modulated by it, which the authors present as evidence of a broad regulatory role over lymphocyte functions rather than a single pathway. [7]
In vitro
- System
- Cultured human CD8 positive T cells under four conditions: untreated, CD3 and CD28 stimulation, peptide alone, and peptide with CD3 and CD28 stimulation, plus an exhaustion model built by repeated stimulation
- Measured
- Proliferation by CFSE flow cytometry, surface CD69, CD25 and HLA-DR, surface PD-1, TIM-3 and LAG-3, and IL-2, IFN-gamma, TNF-alpha and IL-10 by multiplex bead assay
- Reported
- The peptide alone moderately raised proliferation and activation. Combined with CD3 and CD28 stimulation it significantly raised the proliferation index and CD69, CD25 and HLA-DR expression above either condition alone, and raised the four measured cytokines. In the exhaustion model the raised PD-1, TIM-3 and LAG-3 expression was significantly reduced. [8]
Handling for in-vitro work
- Thermal behaviour in cited work
- Described as heat stable in the original isolation, which used repeated chromatographic steps in aqueous buffers [1]
- Solvent in cited structural work
- Dissolved in 40 percent trifluoroethanol and 60 percent water for the NMR structure determination [2]
- Storage
- Lyophilized at -20 °C, dark and dry; reconstituted aliquots kept cold and used promptly
Open questions
- No receptor for the peptide is identified in the cited work; the dendritic cell results run through Toll-like receptor signalling triggered by the accompanying stimulus rather than by a receptor for the peptide itself.
- The direction of the dendritic cell response reversed between viral and bacterial stimuli in the cited work, so a result cannot be read without the stimulus it was measured under.
- The natural peptide is N-alpha-acetylated and one cited paper studied an albumin fusion rather than the free peptide, so the acetylation state and construct of a supplied lot decide which papers it can be compared against.
- The peptide was originally described as one component of a thymic fraction, so material identified only by the thymosin family name is not established to be this sequence.
A clinical literature on this peptide exists and concerns finished formulations; it is out of scope for a research material profile.
Lot records
Check the record for the exact material you order. A published paper and a batch certificate answer different questions.
No published lot is available for this exact compound name.
Read a certificate of analysis ↗References
- Goldstein AL, Low TL, McAdoo M, et al. Thymosin alpha1: isolation and sequence analysis of an immunologically active thymic polypeptide. Proceedings of the National Academy of Sciences of the United States of America. 1977.
- Elizondo-Riojas MA, Chamow SM, Tuthill CW, et al. NMR structure of human thymosin alpha-1. Biochemical and biophysical research communications. 2011.
- Schmidt M, Toplak A, Rozeboom HJ, et al. Design of a substrate-tailored peptiligase variant for the efficient synthesis of thymosin-α1. Organic & biomolecular chemistry. 2018.
- Chen J, Li H, Wang T, et al. Production of Nα-acetyl Tα1-HSA through in vitro acetylation by RimJ. Oncotarget. 2017.
- Giacomini E, Severa M, Cruciani M, et al. Dual effect of Thymosin α 1 on human monocyte-derived dendritic cell in vitro stimulated with viral and bacterial toll-like receptor agonists. Expert opinion on biological therapy. 2015.
- Romani L, Bistoni F, Gaziano R, et al. Thymosin alpha 1 activates dendritic cells for antifungal Th1 resistance through toll-like receptor signaling. Blood. 2004.
- Matteucci C, Minutolo A, Sinibaldi-Vallebona P, et al. Transcription profile of human lymphocytes following in vitro treatment with thymosin alpha-1. Annals of the New York Academy of Sciences. 2010.
- Mishra S, Telang G, Sureshbabu A, et al. Thymosin α1 Augments CD8⁺ T-Cell Activation and Reverses Exhaustion In Vitro. Asian Pacific journal of cancer prevention : APJCP. 2026.
Publication records fetched from PubMed on 2026-09-20. Profile text reviewed 2026-09-20.