AOD-9604 is mixed with bacteriostatic water, and that is the standard solvent for it in research. No measured water solubility figure was available to us, so what follows reasons from the sequence and from the concentrations our own tables use, and says where a figure is missing.
What the sequence says
The sequence Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe is mixed in character. The N-terminal end, Tyr-Leu-Arg-Ile-Val, carries leucine, isoleucine, valine and tyrosine, four hydrophobic residues in five positions, and there is a phenylalanine at the far end. The middle, inside the disulfide ring, is polar: two serines, a glutamate, two glycines and two arginines. PubChem’s computed XLogP for the whole molecule is minus 4.8, a hydrophilic value overall (PubChem CID 71300630), but that single number averages over a molecule with a distinctly greasy end.
Charge gives a second clue. Counting the ionisable groups gives two arginines plus the N-terminal amine against one glutamate side chain and the C-terminal carboxyl. From that count we calculate a net charge of about plus 0.9 at pH 7 and an isoelectric point near pH 8.2. These are our calculations from standard pKa values, not a measured figure. A peptide is least soluble at its isoelectric point, where its charges cancel. Bacteriostatic water is below pH 8.2, so the molecules carry a like positive charge, but the margin is smaller than for a strongly acidic or strongly basic peptide. Treating it gently and giving it time to dissolve is the sensible response.
No supplier figure available
We could not open a chemical supplier data sheet for AOD-9604, and the suppliers quoted on our storage page are cited there for storage, not solubility. So no mg/mL water figure is stated anywhere on these pages. What we can say is that the concentrations in our own tables are the ones the product is prepared at in practice.
Bacteriostatic water first
Bacteriostatic water is sterile water with 0.9% benzyl alcohol, which allows a refrigerated vial to be accessed more than once, and it is the solvent our reconstitution page uses. The preservative supports repeated access over the 8 to 12 week fridge window described on how long AOD-9604 lasts. Sterile water works for a vial that will be accessed once. The difference is explained in bacteriostatic water explained.
Why not acetic acid?
Laboratories sometimes add a little dilute acetic acid to coax hydrophobic peptides into solution, because lowering the pH gives a basic peptide more positive charge. AOD-9604 dissolves at the concentrations our tables use without it, and acid is not a neutral addition: it speeds hydrolysis of peptide bonds generally. Plain bacteriostatic water is the solvent on our pages, and there is no published figure showing acid is needed for this peptide.
Saline and sodium chloride
AOD-9604 is expected to dissolve in 0.9% sodium chloride, but we found no figure for it and our vial is not specified for saline. Salt ions screen the charges on a peptide, which can reduce solubility for peptides that rely on charge repulsion near their isoelectric point, and with a calculated isoelectric point near pH 8.2 this peptide has less charge to spare than most. That is general peptide chemistry plus our calculation, not a measurement. For a multi-access vial, bacteriostatic water remains the choice because of its preservative.
Concentrations in our vial
Our vial is 5 mg. With 2 mL of bacteriostatic water it gives 2.5 mg/mL, and with 5 mL it gives 1 mg/mL; those are the figures the AOD-9604 reconstitution page uses for our vial, alongside tables for the other sizes found in other catalogues. The solution should be clear and colourless.
A larger water volume does not change the amount of peptide; it spreads it more thinly, which also makes small draws easier to read. Whatever volume is chosen, write the concentration on the vial.
Cloudiness and gelling: what causes them
A correctly mixed vial is clear and colourless. Haze usually points to technique or storage rather than the peptide, and for a peptide with a hydrophobic end it is worth avoiding the mechanical causes:
- Water jetted onto the cake. A strong stream can trap air and create foam, which looks cloudy. Running the water down the inside wall of the vial avoids it.
- Shaking. Vigorous agitation creates air and liquid interfaces where peptides can unfold and clump, and this peptide has a hydrophobic N-terminal stretch. Swirl or roll instead, and let any foam settle.
- Cold water onto cold powder. Both at fridge temperature slows dissolving. Letting the vial and the water reach room temperature first helps.
- Haze or gel appearing later in storage. This suggests the vial was kept too warm or bright, frozen and thawed, or contaminated, and the solution is discarded.
Brief cloudiness that clears within 10 to 15 minutes of mixing is normal and usually trapped air. The general causes are covered in why peptides gel or go cloudy, and the mixing method step by step is in how to reconstitute peptides with bacteriostatic water.
Related AOD-9604 pages
How the dissolved peptide behaves over time is on the AOD-9604 stability page, and bench technique is on the AOD-9604 handling page.
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.
