PNC-27

1 Identity

Base synthetic linear peptide, 32 residues, all L and proteinogenic. Chimeric by construction: an N-terminal 15-residue segment corresponding to residues 12-26 of human p53, joined directly to a 17-residue C-terminal leader of the cell-penetrating-peptide (CPP) structural class. Free N-terminal alpha-amino group and free C-terminal carboxylic acid; no acylation, no amidation, no cyclization. No cysteine and therefore no disulfide, which is worth stating because 32-residue peptides in this market are routinely assumed to be disulfide-containing. One methionine, three tryptophans and one serine-rich acidic stretch; six arginines and five lysines give it a strongly basic net charge. The name is A laboratory series designation, not a chemical abbreviation and not a residue range. Closest confusable, and a separate article in this catalog: PNC-28, from the same program and differing in the p53-derived segment; its sequence, formula and mass are carried on its own record and are not asserted here. Not a synonym and not this article: p53 itself.

Sequence

H-Pro-Pro-Leu-Ser-Gln-Glu-Thr-Phe-Ser-Asp-Leu-Trp-Lys-Leu-Leu-Lys-Lys-Trp-Lys-Met-Arg-Arg-Asn-Gln-Phe-Trp-Val-Lys-Val-Gln-Arg-Gly-OH; one-letter PPLSQETFSDLWKLLKKWKMRRNQFWVKVQRG; 32 residues, all L and proteinogenic; free N-terminus, free C-terminal carboxylic acid, no amidation, no acylation, no cyclization, no disulfide. Residues 1-15, PPLSQETFSDLWKLL, correspond to human p53 residues 12-26. Residues 16-32, KKWKMRRNQFWVKVQRG, are the CPP-class leader segment. One point in the common description is wrong on the face of the arithmetic: the literature and the trade describe that leader as "penetratin", but classical penetratin is RQIKIWFQNRRMKWKK and is a different sequence with a different mass (2246.766 average), so "p53-penetratin chimera" is a description of provenance rather than a statement of composition, and a purchase order written on that phrase does not specify a molecule. The sequence above is a supplier claim until MS/MS with full fragment coverage confirms it on the first lot.

Molecular formula

C188H293N53O44S as the free peptide with a free C-terminal acid. Supplied as the acetate salt, which is not a fixed stoichiometry and is specified as a percentage range rather than folded into a formula; on a peptide carrying eleven basic side chains the counterion fraction is large and the shipped mass is peptide plus acetate plus water.

Average mass

4031.799 Da (C188H293N53O44S), from the formula on IUPAC 2021 abridged conventional atomic weights (C 12.011, H 1.008, N 14.007, O 15.999, S 32.06) and independently reconstructed residue by residue from the 32-mer sequence; the two routes agree to the digit. One supplier publishes 4031.72 for the same formula, which is that formula on the pre-2021 atomic-weight table; the 0.08 Da difference is the table, not the molecule, and the basis is stated on the face of the number as it is on every record in this catalog. At this size the average mass is not an identity test at all — a plus or minus 5 ppm window on it is plus or minus 0.02 Da, and no single-residue substitution in a 32-mer is reliably outside a routine deconvolution error.

Monoisotopic mass

4029.20397 Da neutral (C188H293N53O44S); [M+H]+ 4030.21125. The ions actually observed on a peptide of this size and charge are multiply protonated, and the certificate must state which: [M+2H]2+ m/z 2015.6093; [M+3H]3+ m/z 1344.0753; [M+4H]4+ m/z 1008.3083; [M+5H]5+ m/z 806.8481. Identity window at plus or minus 5 ppm on the 3+ ion is plus or minus 0.0067 m/z units. The C-terminal amide is 4028.21996 neutral, 0.984 Da below parent — which at 32 residues is not resolvable on an ordinary instrument at the charge states above and is one of the reasons MS/MS, not accurate mass, is the identity test on this article. Single methionine oxidation gives 4045.19889 neutral, plus 15.995 Da.

Salt / variant note

(1) the identity problem is size, and it is arithmetic. At 4031.799 average a plus or minus 5 ppm window is plus or minus 0.02 Da, and the smallest single-residue substitutions — Leu for Ile (0 Da), Gln for Lys (0.036 Da), Asn for Asp or Gln for Glu (0.984 Da) — are at or below the resolution any routine deconvolution delivers on a 32-mer. Accurate mass is corroboration on this article and never identity, and MS/MS fragment coverage is carried as a printed number on the certificate rather than as an assurance. (2) leucine/isoleucine substitution at any of Leu3, Leu11, Leu14, Leu15: isobaric at every resolution, separable only by MS/MS fragmentation behavior or amino acid analysis, and there are four sites. (3) deamidation and misincorporation at plus or minus 0.984 Da: Asn23 and the three glutamines are the predictable sites, and the C-terminal amide sits at the same 0.984 Da offset in the other direction, so a single mass shift of one dalton on this molecule has at least three chemically distinct explanations. (4) methionine oxidation at Met20, plus 15.995 Da (4047.798 / 4045.19889), and tryptophan oxidation at Trp12, Trp18 and Trp26, plus 15.995 Da each with N-formyl-kynurenine at plus 31.990 — four oxidizable residues in one molecule, which makes oxidation the dominant degradation axis and the 280 nm channel load-bearing. (5) TRUNCATIONS from incomplete synthesis: the des-Pro1 species C183H286N52O43S at 3934.682 / 3932.15121 is one example and the general case is worse — on a 32-mer, deletion sequences from any of 31 couplings are the normal impurity class, they are individually small and collectively large, and they are what a crude preparation is made of. Because of that, the purity acceptance criterion on this article is set at not less than 95.0 percent with a named deletion-sequence limit, rather than at the 98.0 percent this catalog carries on small peptides, and aggregate content by SE-HPLC is specified alongside it because aggregation is a shelf-life mechanism no reversed-phase number sees. (6) the leader-sequence axis, which is a naming failure rather than a chemical one: material sold as "p53-penetratin" built with CLASSICAL penetratin (RQIKIWFQNRRMKWKK, 2246.766) rather than the KKWKMRRNQFWVKVQRG leader in this specification would be a different molecule of different mass sold under the same description. (7) PNC-28, the sibling article from the same program: its sequence, formula and mass are not asserted here; it is a separate purchase specification and is not received against this one. (8) salt and content axis: with eleven basic side chains the acetate fraction is large, and trifluoroacetate lots are refused because residual trifluoroacetate interferes with the cell-culture work that is this article's declared research use. One further market fact belongs with the salt and content question: institutional and consumer pricing on this article sit unusually close together, so on this article price carries no information about how well characterized a lot is and the certificate carries all of it.

2 Class & testing panel

Form

Single article

Testing panel

P1 — panel definition

3 Primary sources & evidence

The index reports the design and provenance of the literature, not a conclusion about effect.

Published literature exists and it is preclinical. Identifiers and study types only. Sarafraz-Yazdi et al., PNAS 2010, PMID 20182728 — in vitro, cancer cell lines. A PNAS-associated structural study of the chimeric peptide's conformation and of membrane-pore formation, deposited at MIT DSpace, PMC2836618 — in vitro, NMR and biophysical. Michaeli, Pincus et al., Cancer Res 2008 supplement abstract LB-195 — in vitro, conference abstract, which is a study type that carries no peer review of a full report. A 2024 European Society of Medicine item on cervical cancer cell work — in vitro. The originating program is at New York Medical College and the literature is substantially single-group; no claim is made about the extent of independent replication outside that group in either direction. No registered human clinical trial has been identified, and that is "none located" rather than "none exist". No pharmacokinetic characterization, no formal toxicology package, no immunogenicity assessment and no regulatory review in any jurisdiction has been located. There is a wide gap between what this article is sold on and what has been published about it, and literature volume by study type is printed at the head of the research page so a reader sees the size of the base before reading a word of it.

4 Storage & specification

Storage

White to off-white lyophilized powder, acetate salt, in amber glass vials with a nitrogen headspace and desiccant; non-sterile, no sterility claim, no stoppered-and-crimped injection format, no dose-shaped vial. -20 degrees C plus or minus 5 degrees C or below, desiccated, protected from light; amber glass and the nitrogen overlay are specification items because one methionine and three tryptophans make oxidation the dominant degradation axis on this molecule, and a nitrogen headspace is the cheapest control available for it. Equilibrate to room temperature sealed before opening. Reconstituted material is aliquoted on receipt and frozen; freeze-thaw cycling is avoided, because on a strongly basic amphipathic 32-mer it promotes aggregation that no purity assay on the release certificate detects. A single excursion to 2-8 degrees C of up to 30 days cumulative is permitted and recorded on the lot record. Shipped on dry ice or gel packs with a temperature logger filed against the shipment.

Shelf life

The retest interval is 24 months at -20 degrees C plus or minus 5 degrees C, supported by this company's own three-lot ICH Q1A-format study — long-term at -20 degrees C, accelerated at 25 degrees C / 60 percent RH, with photostability under ICH Q1B option 2. The stability-indicating attributes are the oxidation products at plus 15.995 and plus 31.990 Da tracked on the 280 nm channel, and aggregate content by SE-HPLC trended alongside them: on a peptide of this length and charge, aggregation is a real shelf-life mechanism that a reversed-phase purity number does not register, and a stability program that trends only RP-HPLC purity will report a stable article while the monomer fraction falls. The interval is shortened on data and never extended without a completed dataset.