LL-37 Reconstitution: How Much Bacteriostatic Water
A 5 mg vial of LL-37 reconstituted with 2 mL of bacteriostatic water gives a concentration of 2.5 mg/mL; with 1 mL it gives 5 mg/mL. The calculation depends only on the quantity in the vial and the volume of water added, so the figures below apply to any 5 mg vial.
There is no single correct volume. Adding more water does not change how much is in the vial. It spreads the same quantity through a larger volume, which changes how many syringe units correspond to a given amount. The tables on this page use volumes that produce round numbers on a U-100 syringe; other volumes work identically as long as the resulting concentration is written on the vial.
Peptide reconstitution calculator
Set to this vial below. Change the vial size, water volume, amount or syringe and it recalculates the concentration and the syringe units. For laboratory research use only.
All products are sold strictly for laboratory research use only and are not for human or veterinary consumption. This calculator is provided as a general reference tool.
How much bacteriostatic water for 5 mg LL-37?
A 5 mg LL-37 vial is commonly reconstituted with 2 mL of bacteriostatic water, which gives 2.5 mg/mL; 1 mL gives 5 mg/mL, 2.5 mL gives 2 mg/mL and 5 mL gives 1 mg/mL. The table shows how much LL-37 each 0.1 mL of solution contains at each volume. Adding more water does not change the 5 mg in the vial; it only lowers the concentration.
| Water added | Concentration | Amount in 0.1 mL (10 units on a U-100 syringe) |
|---|---|---|
| 1 mL | 5 mg/mL | 0.5 mg |
| 2 mL | 2.5 mg/mL | 0.25 mg |
| 2.5 mL | 2 mg/mL | 0.2 mg |
| 5 mL | 1 mg/mL | 0.1 mg |
For any other water volume, enter it in the peptide calculator on this page and it works out the concentration.
Before choosing a larger volume, check that the vial has headspace for it. One multi-dose vial of bacteriostatic water covers several research vials.
Reading the concentration on a U-100 syringe
A U-100 insulin syringe is graduated in units, and 100 units equal 1 mL. Units are therefore millilitres multiplied by 100: 0.1 mL is 10 units and 0.25 mL is 25 units. A 0.5 mL syringe carries 50 units and a 0.3 mL syringe carries 30 units on the same scale, with finer markings that make small volumes easier to read.
To find the volume that contains a given amount, divide the amount by the concentration. At 2.5 mg/mL (a 5 mg vial with 2 mL of water), the volume that contains 0.5 mg is 0.5 divided by 2.5, which is 0.2 mL, or 20 units. The table below runs the same calculation for four arbitrary amounts. They illustrate the arithmetic and nothing else.
| Amount (illustrative) | Volume at 2.5 mg/mL | U-100 units |
|---|---|---|
| 0.1 mg | 0.04 mL | 4 units |
| 0.25 mg | 0.1 mL | 10 units |
| 0.5 mg | 0.2 mL | 20 units |
| 1 mg | 0.4 mL | 40 units |
At 5 mg/mL, which the same vial gives with 1 mL of water, every volume in the table moves in proportion: a 0.5 mg draw measures 10 units instead of 20. Volumes below about 0.1 mL are hard to read accurately on a 1 mL syringe. Either move to a 0.3 mL or 0.5 mL syringe, or reconstitute with more water so that the same mass occupies a larger, more legible volume.
LL-37 is a lyophilised material for laboratory research use only. The quantities on this page illustrate the arithmetic of dilution and measurement only.
What LL-37 is
LL-37 is the human cathelicidin: a 37-amino-acid antimicrobial peptide, named for its two leading leucine residues, cleaved from the precursor protein hCAP18. Besides its antimicrobial activity it has immunomodulatory and proangiogenic properties, and wound healing dominates its human research.
- In the first-in-human trial, 34 participants with hard-to-heal venous leg ulcers received topical LL-37 or placebo over a four-week treatment phase; healing rate constants at 0.5 and 1.6 mg/mL were roughly six and three times higher than placebo, mean ulcer area fell by 68% and 50%, and there were no safety concerns (Grönberg et al., 2014).
- The phase IIb HEAL LL-37 trial in 148 patients found LL-37 well tolerated and safe at both concentrations tested, and a post hoc analysis showed statistically significant improvement in several healing parameters in patients with large ulcers of at least 10 cm² (Mahlapuu et al., 2021).
- In patients with venous leg ulcers, serum LL-37 concentrations were strongly associated with healing rates, while 25-hydroxy vitamin D levels were not (Krejner et al., 2017).
- Synthetic LL-37 showed no apparent cleavage after up to 24 hours at 37 °C in wound fluid from non-healing venous leg ulcers, a result relevant to how stable the peptide is in a protein-rich environment (Grönberg et al., 2011).
The LL-37 vial
LL-37 is commonly supplied in research catalogues as a lyophilised powder in a 5 mg vial. Vistara Labs does not currently stock LL-37, but you can request it: contact us and we will source it for you. The calculator on this page works for any vial. Vistara Labs supplies TB-500, another peptide studied in tissue repair research, as a 10 mg vial.
Reconstitution technique
Let the vial reach room temperature, swab both stoppers, and run the measured water slowly down the inside wall of the vial rather than onto the powder. Swirl or tilt gently until the cake dissolves, never shake, and give any remaining powder a few minutes to settle into solution. Label the vial with the date and the concentration, then keep it refrigerated at 2 to 8 °C and protected from light. The full method, with the reason behind each step, is in how to reconstitute peptides with bacteriostatic water.
Why the solution should look clear
Properly reconstituted LL-37 forms a clear, colourless solution. Cloudiness, strands or a gel that will not disperse usually mean the water went in too fast or the vial was shaken; haze that appears later points to warm or bright storage. The causes are covered in why peptides gel or go cloudy.
Bacteriostatic water, not sterile water
Bacteriostatic water is sterile water with 0.9% benzyl alcohol, a preservative that allows a refrigerated vial to be accessed more than once; plain sterile water is intended for single access. The difference is explained in bacteriostatic water explained.
Frequently asked questions
How much bac water for a 5 mg LL-37 vial?
A 5 mg LL-37 vial is commonly reconstituted with 2 mL of bacteriostatic water, which gives 2.5 mg/mL; 1 mL gives 5 mg/mL, 2.5 mL gives 2 mg/mL and 5 mL gives 1 mg/mL. Adding more water does not change the 5 mg in the vial; it only lowers the concentration.
How many 5 mg vials does one vial of bacteriostatic water cover?
One multi-dose vial of bacteriostatic water covers several research vials. Check that the peptide vial has headspace for the volume before choosing a larger one.
How many units on a U-100 syringe contain 0.5 mg at 2.5 mg/mL?
At 2.5 mg/mL (a 5 mg vial with 2 mL of water), the volume that contains 0.5 mg is 0.5 divided by 2.5, which is 0.2 mL, or 20 units. Units are millilitres multiplied by 100, so 0.1 mL is 10 units. The amounts on this page illustrate the arithmetic only.
What should reconstituted LL-37 look like?
Properly reconstituted LL-37 forms a clear, colourless solution. Cloudiness, strands or a gel that will not disperse usually mean the water went in too fast or the vial was shaken; haze that appears later points to warm or bright storage. More on the causes in why peptides gel or go cloudy.
Can I use sterile water instead of bacteriostatic water?
Only for a vial that will be accessed once. Bacteriostatic water is sterile water with 0.9% benzyl alcohol, a preservative that allows a refrigerated vial to be accessed more than once; plain sterile water is intended for single access. Details in bacteriostatic water explained.
How should a reconstituted LL-37 vial be stored?
Refrigerated at 2 to 8 °C, protected from light and labelled with the date and the concentration. Unopened lyophilised vials are kept cold and dark until they are needed. The full storage guide is how to store research peptides.
Does Vistara Labs sell LL-37?
Vistara Labs does not currently stock LL-37, but you can request it: contact us and we will source it for you. The calculator on this page works for any vial.
Work it out for a different vial or concentration
Our peptide calculator opens pre-set for a 5 mg vial with 2 mL of water and marks the 0.5 mg draw of 20 units on a syringe diagram. Change the vial size, water volume, amount or syringe and it recalculates.
Products: bacteriostatic water.
Sources: Grönberg A et al. Treatment with LL-37 is safe and effective in enhancing healing of hard-to-heal venous leg ulcers: a randomized, placebo-controlled clinical trial. Wound Repair Regen. 2014. PMID 25041740. Mahlapuu M et al. Evaluation of LL-37 in healing of hard-to-heal venous leg ulcers: A multicentric prospective randomized placebo-controlled clinical trial. Wound Repair Regen. 2021. PMID 34687253. Krejner A et al. LL-37 but Not 25-Hydroxy-Vitamin D Serum Level Correlates with Healing of Venous Leg Ulcers. Arch Immunol Ther Exp (Warsz). 2017. PMID 27663530. Grönberg A et al. Stability of the cathelicidin peptide LL-37 in a non-healing wound environment. Acta Derm Venereol. 2011. PMID 21547341.
All products supplied by Vistara Labs are intended for laboratory research use only. They are not drugs, are not approved for human or veterinary use, and are not intended to diagnose, treat, cure or prevent any condition. Nothing on this page constitutes medical advice or guidance for use in humans.
