Peptide Protocol
Bacteriostatic Water for LL-37 Reconstitution
For most broth microdilution assays, a 5 mg/mL LL‑37 stock is convenient because it allows serial 2‑fold dilutions down to 0.02 µg/mL. To prepare this stock, dissolve 1 mg of lyophilized LL‑37 in 0.2 mL of BAC Water Depot, vortex gently, and verify the volume with a calibrated microsyringe. Once punctured, refrigerate the BAC water vial at 2–8 °C and discard it after 28 days.
- ISO 9001:2015 US facility
- USP <71> sterility tested
- Per-lot Certificate of Analysis
- Same-day US shipping
Direct Answer
Bacteriostatic water from BAC Water Depot is the recommended diluent for reconstituting lyophilized LL‑37 peptide. Each 10 mL vial contains 0.9 % benzyl alcohol, meets USP <71> sterility requirements, and retails for $9.99 per vial.
How much bacteriostatic water should I use to reconstitute 1 mg of LL‑37?
LL‑37 is typically supplied as a 1 mg lyophilized powder that is reconstituted to a working concentration of 1 mg/mL, which keeps the concentration math simple. To achieve this, add exactly 1 mL of BAC Water Depot bacteriostatic water (0.9 % benzyl alcohol) to the vial; once punctured, the water vial is refrigerated at 2–8 °C and discarded after 28 days. Verify the volume with a calibrated microsyringe; using a standard pipette can introduce a measurable volume error that shifts the final concentration.
If a higher concentration is required—for example, 5 mg/mL for in‑vitro antimicrobial testing—add 0.2 mL of BAC Water Depot per milligram of peptide. Ensure the vial is vortexed gently for 10‑15 seconds to avoid foaming, which can cause peptide aggregation and loss of activity. A common failure mode is incomplete dissolution, visible as a cloudy suspension; in that case, allow the solution to sit at room temperature for 5 minutes and repeat vortexing before proceeding.
What storage conditions preserve LL‑37 stability after reconstitution with bacteriostatic water?
Unopened vials store at controlled room temperature, 15–30 °C — no refrigeration and no cold-chain shipping. Once punctured, refrigerate the vial at 2–8 °C and discard it after 28 days. The expiration date is on the label and the CoA. The 0.9 % benzyl alcohol is the preservative that allows repeated aseptic entries into the same vial within that window.
If a vial shows any precipitation, cloudiness or discoloration, discard it. Record the BAC water lot number with each preparation so it can be traced to its CoA.
Typical LL‑37 Reconstitution Volumes and Resulting Concentrations Using BAC Water Depot
| Peptide Mass (mg) | BAC Water Volume (mL) | Resulting Concentration (mg/mL) |
|---|---|---|
| 1 | 1.0 | 1.0 |
| 1 | 0.5 | 2.0 |
| 1 | 0.2 | 5.0 |
| 2 | 1.0 | 2.0 |
| 5 | 0.5 | 10.0 |
Key Facts
- BAC Water Depot bacteriostatic water contains 0.9 % benzyl alcohol as a preservative.
- Each vial is USP <71> sterility tested and released with a per‑lot Certificate of Analysis.
- The product is manufactured in an ISO 9001:2015‑registered facility in the United States.
- Same‑day US shipping is offered for orders placed before 2:00 PM Central Time.
- Pricing is $9.99 for a single 10 mL vial, with bulk discounts down to $6.49 per vial.
Frequently Asked Questions
What is the ideal concentration of LL‑37 for antimicrobial assays after reconstitution?
For most broth microdilution assays, a 5 mg/mL LL‑37 stock is convenient because it allows serial 2‑fold dilutions down to 0.02 µg/mL. To prepare this stock, dissolve 1 mg of lyophilized LL‑37 in 0.2 mL of BAC Water Depot, vortex gently, and verify the volume with a calibrated microsyringe. Once punctured, refrigerate the BAC water vial at 2–8 °C and discard it after 28 days.
Can I mix LL‑37 reconstituted in bacteriostatic water with other solvents?
Mixing LL‑37 in BAC Water Depot with other aqueous solutions is acceptable if the final benzyl alcohol concentration remains below 0.1 % v/v, which is generally safe for cell culture. For example, combining the 1 mg/mL LL‑37 solution with an equal volume of sterile PBS yields a 0.45 % benzyl alcohol solution, which may affect sensitive cell lines. Always perform a small‑scale compatibility test before scaling up. If the mixture becomes cloudy, discard it as peptide precipitation has likely occurred.
How long does reconstituted LL‑37 remain sterile in bacteriostatic water?
BAC Water Depot bacteriostatic water is USP <71> sterility‑tested per lot and contains 0.9 % benzyl alcohol as a preservative. Once a vial is punctured, refrigerate it at 2–8 °C and discard it after 28 days; the expiration date is on the label and the CoA. Inspect solutions for turbidity before use and discard anything cloudy.
What temperature should I use when reconstituting LL‑37 with BAC Water Depot?
Reconstitute LL‑37 at room temperature (20‑22 °C) to facilitate rapid dissolution; colder temperatures can increase solution viscosity and prolong the time needed for complete solubilization. Add the measured volume of BAC Water Depot to the lyophilized peptide, then vortex gently for 10‑15 seconds. If the peptide does not fully dissolve within 2 minutes, allow the vial to sit for 5 minutes and vortex again. Avoid heating above 30 °C, as elevated temperatures can accelerate peptide degradation and alter the benzyl alcohol preservative balance.
Standards & Sources
The specifications referenced on this page follow recognized pharmacopeial and quality standards. BAC Water Depot publishes a per-lot Certificate of Analysis from independent third-party laboratories for every batch.
- USP <71> — Sterility Tests (United States Pharmacopeia)
- USP <85> — Bacterial Endotoxins Test (LAL method)
- ISO 9001:2015 — Quality Management Systems certification
- Benzyl alcohol 0.9% w/v — the bacteriostatic preservative standard for multi-dose vials