P21 (P021): preparation and storage
Intended for research use only. Not a medicinal product.
Contents (8 sections)
Identity and material form
In this catalogue, P21 means P021, a small synthetic peptidergic compound developed from research on ciliary neurotrophic factor, CNTF. It is distinct from the cell-cycle protein p21/CDKN1A and from full-length CNTF. Searching only for “p21” often leads to antibodies and recombinant proteins with different buffer requirements. Write P021 in full on laboratory labels.
Identification requires the structural formula, terminal modifications and catalogue identifier. The compound contains modifications that can make an unexplained amino-acid shorthand ambiguous. Do not reconstruct the structure from the name or calculate its mass from an assumed sequence. MedChemExpress lists 578.66 g/mol for its P021; using that number for another salt or product requires verification.
What the research context means
Kazim and colleagues studied chronic oral P021 treatment in a triple-transgenic mouse model of Alzheimer's disease [1]. It does not make every vial labelled P21 a reproduction of the experiment or provide a stability specification for a current P021 batch.
For replication, check the exact compound and preparation in the methods, together with the exposure route. Incorporation into feed, systemic exposure in an animal and addition to culture medium have different sources of variability. For a feed matrix, distribution uniformity and quantitative extraction from feed need their own validation; the concentration of the starting solution does not establish either.
Solvent and final matrix
A modified short peptide does not necessarily behave like an unmodified water-soluble CNTF sequence. Select the solvent from documents for P021 itself. Catalogue information for recombinant CNTF or p21 protein does not apply. Adding albumin as a “stabiliser” by analogy with a protein growth factor lacks a basis unless validated: it may affect the free compound fraction and analytical recovery, which need checking.
Start with a small sample and check it after dilution into the final matrix. If the method requires DMSO, account for its fraction in every well and control. A clear concentrated stock can form microprecipitates after extensive aqueous dilution. Check immediately after mixing and at the end of the planned exposure, rather than only in the original vial.
Laboratory calculation example
A mass-dilution example avoids assumptions about the salt: bring 2.00 mg of quantitatively transferred material to a final 2.00 mL, giving a nominal 1.00 mg/mL. Transfer 100 µL into a final 1.00 mL to obtain 0.100 mg/mL. Repeating that dilution gives 0.0100 mg/mL. State whether mass means P021 itself or total lyophilisate.
If the starting stock contained 100% DMSO, the first and second aqueous stages contain 10% and 1% DMSO respectively. Those fractions may be incompatible with a particular cell method. The arithmetic shows why intermediate dilutions and vehicle controls need a separate plan. It does not select these concentrations for biological experiments or establish DMSO as a universal recipe.
Quality checks during handling
For P021, the LC-MS identity check must match the actual modified structure. A “correct mass” peak without chromatographic separation does not exclude related impurities. To assess solubility, measure quantitative recovery in the soluble fraction; visible precipitate and clarity are preliminary observations.
Prepare highly dilute working samples for the required experiment series unless longer storage is validated. Relative losses to surfaces or precipitation may be greater at this stage. When investigating low recovery, avoid changing the tube type, solvent and holding time simultaneously.
Dry material and solution need separate conditions
For long-term storage of a dry synthetic peptide, use a freezer, commonly −20 °C or below, where the specification supports it. Allow the sealed vial to reach room temperature before opening so moisture does not condense on cold powder. A refrigerator at +2–8 °C can be a working option for dry material needed within a week or a month only when the supplier supports that interval. Planning to use a vial soon does not establish its shelf life.
A solution needs its own record: solvent, concentration, pH, preparation date, temperature and permitted holding time. Do not transfer the dry-material expiry to the solution. Where freezing is supported, prepare aliquots for individual experiments; thawing the remainder again needs separate validation. Bacteriostatic water contains a preservative that can change a cell-assay result and is not a default solvent for every peptide.
Practical questions
Does a protocol for p21 protein apply? No. It concerns another material; recombinant protein-folding requirements do not describe P021. Does oral exposure in an animal experiment mean an aqueous solution lasts a month? No: the exposure route is not a storage study.
Can prepared culture medium containing P021 be frozen? Both the compound and the medium need checking after a freeze cycle. Stability of a concentrated stock in one solvent does not establish stability of a dilute mixture containing proteins and salts.
Monograph · Product page · Certificates of analysis
General reagent preparation · Bacteriostatic water compatibility · Storage and expiry
Sources
- Kazim Syed Faraz, Blanchard Julie, Dai Chun-Ling, Tung Yunn-Chyn. Disease modifying effect of chronic oral treatment with a neurotrophic peptidergic compound in a triple transgenic mouse model of Alzheimer's disease. 2014.
MedChemExpress: p21. Reference characteristics of that catalogue material; not a specification for a Longeva batch.
End of article
P21 (P021)
for laboratory research
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