TB-500 Testing: HPLC Purity and Identity Verification

TB-500 Testing Overview

TB-500 is a synthetic version of thymosin beta-4, a 43-amino-acid peptide with a molecular weight of 4,963.44 Da (for the full sequence) or approximately 2,500 Da for the commonly sold shortened fragment (LKKTETQ). Because TB-500 is sold in multiple fragment lengths, it is critical to know which version you are testing and what molecular weight to expect.

HPLC Purity Analysis

TB-500 is analyzed by reverse-phase HPLC on a C18 column. The purity threshold depends on the fragment:

• Full-length thymosin beta-4: ≥98% purity, MW 4,963.44 Da
• TB-500 fragment (LKKTETQ): ≥98% purity, MW ~820 Da
• Common 17-aa fragment: ≥98% purity, MW ~1,800 Da

Always specify which fragment you are testing when sending a sample to the lab.

LC-MS Identity Confirmation

LC-MS is essential for TB-500 because different fragment lengths have very different molecular weights. The mass spectrum will immediately reveal whether you received the full-length peptide or a shorter fragment. This is one of the most common issues with TB-500 products — vendors may sell a short fragment while labeling it as full-length thymosin beta-4.

Common TB-500 Testing Issues

• Fragment substitution: Short fragment sold as full-length. LC-MS reveals the actual molecular weight.
• Low fill weight: Vial contains less peptide than labeled. Fill weight measurement detects this.
• Aggregation: TB-500 can aggregate in solution, causing broad HPLC peaks. Reconstitute fresh before testing.
• TFA contamination: Residual trifluoroacetic acid from synthesis, which can affect biological assays.