Reconstituting TB-500 for Research: A Step-by-Step Laboratory Guide TB-500 (Thymosin Beta-4 actin-binding fragment, sequence Ac-LKKTETQ, MW 4963.5 g/mol) is supplied as a lyophilised white powder in a 10mL sterile glass vial containing 5mg of peptide. TB-500 is among the most water-soluble research peptides and reconstitutes readily with bacteriostatic water, making it straightforward to prepare for cytoskeletal dynamics, cell migration, and connective tissue cell model research applications. Materials Required TB-500 5mg lyophilised vial Bacteriostatic water (BAC water) — 10mL vial 1mL or 2mL sterile syringe with needle Alcohol swabs (70% isopropyl) Nitrile gloves Permanent marker for labelling Refrigerator at 2–8°C for storage Pre-Reconstitution Preparation Inspect the TB-500 vial to confirm the lyophilised powder is intact — it should appear as a white to off-white fluffy powder or cake with an unbroken vial seal. Remove from cold storage and allow the vial to equilibrate to room temperature for 10 minutes before reconstitution. This prevents condensation from entering the vial and ensures the solvent distributes evenly across the powder during dissolution. Step-by-Step Reconstitution Protocol Step 1 — Clean your workspace. Wipe down the work surface with 70% isopropyl alcohol and allow to air dry. Wear nitrile gloves throughout to maintain aseptic technique. Step 2 — Swab both vial stoppers. Using separate fresh alcohol swabs, clean the rubber stopper of the TB-500 vial and the BAC water vial. Allow to air dry for 10 seconds before proceeding. Step 3 — Draw 2mL of bacteriostatic water. Using a sterile syringe, draw 2mL from the BAC water vial. Bacteriostatic water is strongly preferred over plain sterile water for TB-500 reconstitution as the benzyl alcohol preservative prevents microbial growth during the multi-week refrigerated storage period. Step 4 — Inject slowly along the inner glass wall. Insert the needle into the TB-500 vial and angle it so the BAC water stream flows down the inner glass wall rather than directly onto the powder. Inject slowly over 10–15 seconds. This technique ensures gentle, even wetting of the lyophilised peptide from all sides rather than disrupting the powder structure with a direct stream. Step 5 — Dissolve by gentle swirling. TB-500 is highly water-soluble and dissolves very quickly in aqueous media. Gently swirl the vial for 15–30 seconds — the solution should become clear and colourless rapidly. Do not shake or vortex the vial. While TB-500 is robust compared to many peptides, unnecessary mechanical agitation is best avoided as a matter of standard peptide handling practice. Step 6 — Inspect the solution. Confirm the solution is fully clear with no undissolved powder visible. TB-500 at 2.5mg/mL in BAC water produces a clear, colourless solution. Any persistent cloudiness is unusual and may indicate a vial integrity issue. Step 7 — Label the vial. Record the reconstitution date, resulting concentration, and your initials. Note the expiry date as 28 days from reconstitution. Resulting Concentration Adding 2mL BAC water to a 5mg TB-500 vial yields a stock concentration of 2.5mg/mL (2500mcg/mL). For actin dynamics and cell migration assay applications, working concentrations of 100ng/mL to 10mcg/mL are typical, prepared by serial dilution into sterile PBS or serum-free cell culture media immediately prior to assay. Concentration Reference Table BAC Water Volume AddedResulting Concentration 1mL5.0mg/mL (5000mcg/mL) 2mL2.5mg/mL (2500mcg/mL) 5mL1.0mg/mL (1000mcg/mL) Storage Conditions and Stability Store lyophilised TB-500 at −20°C prior to reconstitution, protected from light and moisture. Once reconstituted with BAC water, store at 2–8°C in the refrigerator. Reconstituted TB-500 is stable for up to 28 days under refrigeration. TB-500 is stable across a wide pH range (5.0–8.0) and is compatible with standard PBS and cell culture media formulations. Do not freeze the reconstituted solution. For long-term working stock storage, aliquot into single-use microcentrifuge tubes and store at −80°C, avoiding repeated freeze-thaw cycles which can promote peptide aggregation over time. Research Application Notes TB-500's high aqueous solubility means it does not require DMSO, acetic acid, or other co-solvents for reconstitution, which simplifies cell model assay preparation and avoids solvent-related cytotoxicity concerns at working concentrations. When diluting for fibroblast scratch wound or Boyden chamber migration assays, prepare working dilutions in the assay media immediately before adding to cells to ensure concentration accuracy. For G-actin sequestration assays in cell-free systems, dilute reconstituted stock into the appropriate assay buffer (typically G-buffer: 2mM Tris-HCl pH 8.0, 0.2mM CaCl2, 0.2mM ATP, 0.5mM DTT). TB-500 5mg vials are available from Pinnacle Peptides, verified at ≥99% purity by HPLC and mass spectrometry. All content is intended for in vitro laboratory research purposes only. Not for human or animal consumption. Not intended to diagnose, treat, cure, or prevent any condition.