The questions below are the ones researchers ask most about storing, mixing and handling PT-141. Each answer reflects its structure, the cyclic heptapeptide Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH, and links to the fuller page where there is one.
How long does PT-141 last in the fridge after mixing?
Mixed with bacteriostatic water and kept at 2 to 8 °C in the dark, PT-141 lasts 8 to 12 weeks under Vistara Labs’ handling guidance, with quality slowly fading from around week 6 to 8. No published stability study of PT-141 in bacteriostatic water was found, so the window is general peptide guidance. The full table is on how long PT-141 lasts.
How long does unmixed PT-141 powder last?
A sealed lyophilised vial is PT-141 at its most stable. One supplier rates the powder, sealed and away from moisture, at 1 year at minus 20 °C and 2 years at minus 80 °C (MedChemExpress, HY-18678). The freezer is for long holds and the fridge for the weeks a vial is in use, boxed and dark.
Why does PT-141 need to be kept out of the light?
Because it carries a tryptophan, the residue that absorbs ultraviolet light and is among those most open to oxidation, with a histidine as a second. No light study of PT-141 itself was found, so the practice is the general one applied with more care: keep the vial boxed and the spray bottle out of sunlight.
What is the difference between PT-141 and Melanotan II?
One position. They are the same cyclic heptapeptide; PT-141 ends in a free carboxylic acid and Melanotan II in an amide. That changes the charge and the solubility behaviour, and the two are studied at different melanocortin receptors. The chemistry of the other is in the Melanotan II research reference.
What do you mix PT-141 with?
Bacteriostatic water, which is sterile water with 0.9% benzyl alcohol so a refrigerated vial can be accessed more than once. A supplier gives water at 100 mg/mL with ultrasound, far above the concentrations our tables use, so it dissolves readily. The details are on the PT-141 solubility guide.
How much bacteriostatic water goes in a 10 mg PT-141 vial?
There is no single correct volume. With 2 mL a 10 mg vial gives 5 mg/mL; with 1 mL it gives 10 mg/mL. More water spreads the same amount of peptide through a larger volume, so write the chosen concentration on the vial. The tables and calculator are on the PT-141 reconstitution page.
Should PT-141 be dissolved in acetic acid?
No. It dissolves well below its supplier’s water figure without help, and acid speeds hydrolysis of peptide bonds. Its calculated isoelectric point, near pH 9.2, also gives no reason to think lowering the pH would improve solubility much.
Why is my PT-141 cloudy after mixing?
Brief cloudiness that clears within 10 to 15 minutes is usually trapped air from adding water too fast or shaking. Haze, particles, gel or a tint that appear later point to warm or bright storage, freezing or contamination, and the solution is discarded. More in why peptides gel or go cloudy.
Can you freeze mixed PT-141?
Not a vial that will be opened again, because repeated freezing and thawing promotes aggregation in peptide solutions and warms the solution each time. The supplier’s frozen-solution figures, 1 month at minus 20 °C and 6 months at minus 80 °C, are for a stock solution frozen once (MedChemExpress, HY-18678). Sealed powder can be frozen, and the ready-mixed spray never is.
How should PT-141 nasal spray be stored?
At 2 to 8 °C, upright, capped and out of the light, and never frozen, the same way as a mixed vial. It arrives ready-mixed, so it goes into the fridge as soon as it arrives. The routine is in how to store a peptide nasal spray.
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.
