PT-141 Reconstitution Guide: Step-by-Step Protocol for Laboratory Research
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PT-141 Reconstitution Guide: Step-by-Step Protocol for Laboratory Research
PT-141 (Bremelanotide, cyclo[Nle4,D-Phe7]-alpha-MSH fragment, MW 1025.16 g/mol, CAS 189691-06-3) is a cyclic heptapeptide melanocortin receptor agonist supplied as a lyophilised white powder in a 10mL sterile glass vial containing 10mg of peptide. Its cyclic lactam structure — formed by a Glu4-Lys7 side chain bridge — confers exceptional stability in aqueous media, making reconstitution straightforward for MC3R and MC4R receptor pharmacology research in neuronal cell model systems.
Materials Required
PT-141 10mg 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 PT-141 vial to confirm the lyophilised powder is white, intact, and the vial seal is secure. Remove from cold storage and allow to equilibrate to room temperature for 10 minutes. PT-141's cyclic structure and relatively low molecular weight mean it dissolves very readily — equilibration is primarily to prevent condensation entering the vial.
Step-by-Step Reconstitution Protocol
Step 1 — Prepare workspace. Clean the work surface with 70% isopropyl alcohol and allow to dry fully. Wear nitrile gloves throughout.
Step 2 — Swab both stoppers. Wipe the rubber stopper of both the PT-141 vial and BAC water vial with separate fresh alcohol swabs. Air dry for 10 seconds.
Step 3 — Draw 2mL of BAC water. Using a sterile syringe, draw 2mL of bacteriostatic water. For a 10mg vial, 2mL yields a stock concentration of 5mg/mL. Alternatively, draw 4mL for a 2.5mg/mL stock if lower initial concentration is preferred for your assay design.
Step 4 — Inject slowly along the vial wall. Insert the needle into the PT-141 vial and direct the BAC water slowly down the inner glass wall over 15 seconds. Do not inject directly onto the powder cake.
Step 5 — Dissolve gently. Gently swirl the vial for 20–30 seconds. PT-141 dissolves very readily and the solution should become clear and colourless quickly. Do not shake or vortex.
Step 6 — Inspect and label. Confirm full clarity of the solution. Label the vial with reconstitution date, concentration, and initials.
Resulting Concentration
Adding 2mL BAC water to a 10mg PT-141 vial yields a stock concentration of 5mg/mL (5000mcg/mL). For MC4R receptor binding assays and cAMP accumulation studies in HEK293-hMC4R or GT1-7 neuronal cell model preparations, working concentrations of 0.01nM–1µM are prepared by serial dilution into assay buffer or serum-free media.
Concentration Reference Table
BAC Water Volume AddedResulting Concentration
1mL10.0mg/mL (10000mcg/mL)
2mL5.0mg/mL (5000mcg/mL)
4mL2.5mg/mL (2500mcg/mL)
Storage Conditions and Stability
Store lyophilised PT-141 at −20°C prior to reconstitution, protected from light and moisture. Once reconstituted, store at 2–8°C. Reconstituted PT-141 in BAC water is stable for up to 28 days under refrigeration. Do not freeze reconstituted solution. PT-141's cyclic lactam structure provides excellent stability against proteolytic degradation in serum-containing cell culture media — unlike linear peptides, PT-141 does not require DPP-IV inhibitor supplementation or serum-free conditions to maintain compound integrity during standard assay incubation periods. This stability is a key advantage for neuronal cell model research protocols requiring prolonged compound exposure.
Research Application Notes
PT-141 is freely soluble in BAC water and standard aqueous buffers without co-solvent requirements. Its cyclic structure confers stability across a wide pH range (4.0–9.0) and in protease-rich environments, making it reliable in diverse cell model assay conditions. For MC4R concentration-response studies in GT1-7 or HEK293-hMC4R cell models, serial dilutions should span at least 8 concentration points across a 0.01nM–1µM range to capture the full sigmoidal response curve. When studying MC4R constitutive activity, include inverse agonist AgRP(83-132) as a negative control to establish the minimum activity floor against which PT-141 agonism is quantified. PT-141 10mg 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.
