Thymosin β4 and TB-500 compared

TB-500 is residues 17–23 of thymosin β4, LKKTETQ, with an acetyl group on its N-terminal leucine. Thymosin β4 is the full 43-residue, N-acetylated peptide.

Sequences side by side

TB-500 is a continuous stretch of Thymosin β4: 7 residues in common, aligned below by Thymosin β4's numbering. In each column the upper residue is Thymosin β4's and the lower is TB-500's. Positions outside the shorter sequence are dimmed.

Both have the same termini: N-acetyl and free acid.

Calculated properties

Calculated from each structure

Property	Thymosin β4	TB-500	Difference (TB-500 − Thymosin β4)
Residues	43	7	−36
Molecular formula	C212H350N56O78S	C38H68N10O14
Monoisotopic mass (Da)	4,960.4863	888.4916	−4,071.9947
Average mass (g/mol)	4,963.51	889.02	−4,074.49
Net charge at pH 7	-3.0	0.0	+3.0
Isoelectric point	4.50	7.36	+2.86
Hydropathy (GRAVY)	-1.70	-1.77	−0.07
ε280 (M−1 cm−1)	0	0

Telling them apart by mass spectrometry

The monoisotopic masses differ by 4,071.9947 Da, which any routine mass spectrometer resolves.

Expected protonated ions (monoisotopic m/z)

Ion	Thymosin β4	TB-500
[M+H]+	4,961.4936	889.4989
[M+2H]2+	2,481.2504	445.2531
[M+3H]3+	1,654.5027	297.1712
[M+4H]4+	1,241.1289	223.1302

Telling them apart by HPLC

They differ greatly in size (43 and 7 residues), so their reversed-phase retention cannot be estimated from average hydropathy; size, charge and the residues at the ends all contribute. They are usually well separated. Retention depends on the whole molecule and on the method, so the order is confirmed by running both, or by mass spectrometry of each peak.

Analytical variants each can form

The sequence-specific variants from each entry. A variant only one of them can form is a quick way to tell which is which, and a reminder of what to look for in each.

Sequence-specific variants

Variant	Mass change	Thymosin β4	TB-500
Methionine oxidation	+15.995 Da per oxidized residue	Yes	No
Asparagine deamidation	+0.984 Da	Yes	No
Glutamine deamidation	+0.984 Da	Yes	Yes

Full details, with isotope patterns and fragment ions, are on each entry: Thymosin β4 and TB-500. Both are compared with the rest of their family on the family page.

Sources & Further Reading

1. Prohaska T, Irrgeher J, Benefield J, Böhlke JK, Chesson LA, Coplen TB, et al. Standard atomic weights of the elements 2021 (IUPAC Technical Report). Pure and Applied Chemistry 2022;94(5):573–600. doi:10.1515/pac-2019-0603
2. Wang M, Huang WJ, Kondev FG, Audi G, Naimi S. The AME 2020 atomic mass evaluation (II). Tables, graphs and references. Chinese Physics C 2021;45(3):030003. doi:10.1088/1674-1137/abddaf
3. Rice P, Longden I, Bleasby A. EMBOSS: the European Molecular Biology Open Software Suite. Trends in Genetics 2000;16(6):276–277. doi:10.1016/S0168-9525(00)02024-2
4. Pace CN, Vajdos F, Fee L, Grimsley G, Gray T. How to measure and predict the molar absorption coefficient of a protein. Protein Science 1995;4(11):2411–2423. doi:10.1002/pro.5560041120
5. Kyte J, Doolittle RF. A simple method for displaying the hydropathic character of a protein. Journal of Molecular Biology 1982;157(1):105–132. doi:10.1016/0022-2836(82)90515-0
6. Meija J, Coplen TB, Berglund M, Brand WA, De Bièvre P, Gröning M, et al. Isotopic compositions of the elements 2013 (IUPAC Technical Report). Pure and Applied Chemistry 2016;88(3):293–306. doi:10.1515/pac-2015-0503
7. Roepstorff P, Fohlman J. Letter to the editors: proposal for a common nomenclature for sequence ions in mass spectra of peptides. Biomedical Mass Spectrometry 1984;11(11):601. doi:10.1002/bms.1200111109
8. Biemann K. Contributions of mass spectrometry to peptide and protein structure. Biomedical and Environmental Mass Spectrometry 1988;16(1–12):99–111. doi:10.1002/bms.1200160119
9. Geiger T, Clarke S. Deamidation, isomerization, and racemization at asparaginyl and aspartyl residues in peptides. Succinimide-linked reactions that contribute to protein degradation. Journal of Biological Chemistry 1987;262(2):785–794. doi:10.1016/S0021-9258(19)75855-4
10. Manning MC, Chou DK, Murphy BM, Payne RW, Katayama DS. Stability of protein pharmaceuticals: an update. Pharmaceutical Research 2010;27(4):544–575. doi:10.1007/s11095-009-0045-6
11. D'Hondt M, Bracke N, Taevernier L, Gevaert B, Verbeke F, Wynendaele E, et al. Related impurities in peptide medicines. Journal of Pharmaceutical and Biomedical Analysis 2014;101:2–30. doi:10.1016/j.jpba.2014.06.012

Cosmic Peptides. (2026, October 25). Thymosin β4 and TB-500 compared. Cosmic Peptides Research Library. Retrieved October 26, 2026, from https://cosmicpeptides.com/research/peptides/compare/thymosin-beta-4-vs-tb-500

@misc{cosmicpeptides_research_peptides_compare_thymosin_beta_4_vs_tb_500,
  author       = {{Cosmic Peptides}},
  title        = {Thymosin β4 and TB-500 compared},
  howpublished = {Cosmic Peptides Research Library},
  year         = {2026},
  month        = oct,
  url          = {https://cosmicpeptides.com/research/peptides/compare/thymosin-beta-4-vs-tb-500},
  urldate      = {2026-10-26},
  note         = {Last reviewed 2026-10-25}
}

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