TB-500 (Thymosin Beta-4 fragment) vs Thymosin Alpha-1
Two completely different molecules with confusingly similar names. TB-500 is a soft-tissue and recovery peptide derived from Thymosin Beta-4. Thymosin Alpha-1 is an immune-modulating peptide used in oncology and chronic infection research. Vendors sometimes mix them up. Buyers always should not.
TB-500 (Thymosin Beta-4 fragment)
Thymosin Alpha-1
Parent protein
Thymosin Beta-4 (43 aa)
Prothymosin Alpha
Length sold
17 aa (TB-500 fragment)
28 aa (full)
Molecular weight
~1888 Da
~3108 Da
Primary research focus
Soft tissue, recovery, cardiac
Immune modulation, T-cell activity
Typical research dose
2-2.5 mg twice weekly
1.6 mg twice weekly
Half-life
2-3 days
~2 hours
Approval status
Research only
Approved in 35+ countries (Zadaxin)
Identity (LC-MS) expected mass
~1888 Da
~3108 Da
Common mix-up
Sold AS Thymosin Alpha-1 by mistake
Sold AS TB-500 by mistake
Verdict
Different families, different doses, different end uses. The vial label is not enough - a 1200 Da mass gap is huge and trivial to verify by LC-MS. If you bought either from a vendor that doesn't publish a CoA, get one done before you reconstitute.
Frequently asked questions
Are they interchangeable?
No. TB-500 is soft-tissue recovery; Thymosin Alpha-1 is immune modulation. Wrong-molecule risk is real.
Why is Thymosin Alpha-1 so much more expensive?
It's an approved pharmaceutical in many countries (Zadaxin) used in hepatitis C and cancer protocols. Real material is harder to source.
What if my vial mass comes back wrong?
Stop using it. Contact the vendor with the CoA; LabDoc results are independently verifiable and accepted as evidence in chargebacks.