Humanin

1 Identity

Chemically synthesized 24-residue peptide whose sequence is encoded in the mitochondrial MT-RNR2 open reading frame. All-L, all proteinogenic, one free cysteine thiol. The name is already collapsed in this market: HNG, also written S14G-humanin or [Gly14]-humanin, CAS 330936-70-4.

Sequence

H-Met-Ala-Pro-Arg-Gly-Phe-Ser-Cys-Leu-Leu-Leu-Leu-Thr-Ser-Glu-Ile-Asp-Leu-Pro-Val-Lys-Arg-Arg-Ala-OH; one-letter MAPRGFSCLLLLTSEIDLPVKRRA, 24 residues. Free N-terminal amine, free C-terminal carboxylic acid. No amidation, no acetylation, no acylation, no PEGylation, no metal center, no glycosylation. All-L and no non-proteinogenic residues, stated explicitly so that P3 is not applied by reflex. Three attributes drive every downstream decision on this record. Cys8 carries a free thiol and is not disulfide-bonded within the monomer, which makes the interchain disulfide dimer this molecule's principal degradant rather than a synthesis impurity, and which is why the packaging carries an inert headspace and the retest interval is shorter than the catalog default. Met1 is oxidation-labile at +15.995 Da. The leucine-rich Leu9-Leu12 stretch makes the sequence markedly hydrophobic and aggregation-prone. Position 14 is a serine, and that single residue is what separates this article from the analogue the market sells under the same name. The 24-residue form is what the MT-RNR2 open reading frame yields when read with the mitochondrial genetic code; nuclear-encoded homologues read with the standard code yield a 21-residue peptide, and the two are not interchangeable. Every institutional source located supplies it as the trifluoroacetate salt.

Molecular formula

C119H204N34O32S2 (free base, C-terminal free acid).

Average mass

2687.267 Da (C119H204N34O32S2) on IUPAC 2021 abridged conventional atomic weights; listings commonly print 2687.27. On the older pre-2021 conventional set the same formula gives 2687.23, and one institutional catalog states MW 2687.3 — one molecule, three tables, no disagreement. Note that one institutional supplier publishes "MW 2685.48" for this article, which is the monoisotopic value printed in an average-mass field. It is not a different molecule and it is not an error of chemistry, but a certificate that copies it into an average-mass acceptance criterion will fail a correct lot.

Monoisotopic mass

2685.4822 Da neutral. [M+H]+ 2686.4895; [M+2H]2+ 1343.7484; [M+3H]3+ 896.1680. All of these follow from the stated formula. The identity window is a number, not a phrase: plus or minus 10 ppm on 2685.4822 is plus or minus 0.027 Da, and a result 30.011 Da light is HNG.

Salt / variant note

This is a genuine two-molecules-one-name case, and the market has already collapsed the names. (1) Native humanin, C119H204N34O32S2, 2687.27 / 2685.4822, CAS 330936-69-1 — this record. (2) HNG, also written S14G-humanin or [Gly14]-humanin, C118H202N34O31S2, 2657.24 / 2655.4717, [M+H]+ 2656.4790, CAS 330936-70-4 — exactly 30.011 Da lighter, the difference between a serine and a glycine residue at position 14. It is separately cataloged by several institutional suppliers, one of which gives its molecular weight as 2657.25. Thirty daltons on 2,685 is about 11,000 ppm and no instrument can miss it. The risk sits on the paperwork rather than on the instrument: a certificate can print one molecule's calculated mass above data that were acquired on the other. (3) Humanin(1-21), MAPRGFSCLLLLTSEIDLPVK, C104H175N25O29S2, 2303.81 / 2302.2429, 383.24 Da lighter — the 21-residue congener read with the standard rather than the mitochondrial genetic code. (4) The interchain disulfide dimer, C238H406N68O64S4, 5372.52 / 5368.9488 — this molecule's principal degradant rather than a synthesis impurity, produced by the free Cys8 thiol on storage without an inert headspace. (5) Met1 sulfoxide, C119H204N34O33S2, 2703.27 / 2701.4771, +15.995 Da. (6) Des-Met1 humanin, residues 2-24, C114H195N33O31S, 2556.07 / 2554.4417, -131.04 Da. (7) Trifluoroacetate adducts: the institutional articles are explicitly TFA salts, and a 24-mer carrying three arginines and a lysine holds several; at +114.02 Da average each, quoted molecular weights near 2801, 2915 and 3029 are salt masses and not the peptide. (8) Single-center epimers of any of the 23 chiral residues: exactly isobaric and co-eluting on achiral columns. All of these masses follow from the stated formulas.

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 is substantial in vitro: a well-developed in-vitro literature since 2001 — cell-culture assay work, characterization of the binding partners, and structure-activity work on the 24-mer and its analogues — together with a growing rodent literature. Human work is almost entirely observational: measurement of circulating peptide in cohorts, and association studies against age and mitochondrial haplogroup. No controlled human trial of administered humanin has been published, and no registered clinical trial of the native 24-residue peptide appears in ClinicalTrials.gov. One limitation is material enough to state here rather than bury in a footnote: a large share of the animal work uses the S14G analogue rather than the native sequence, so that literature does not transfer to this article without an explicit caveat.

4 Storage & specification

Storage

White lyophilized powder in a Type I amber glass vial with a PTFE-lined closure; a laboratory-chemical presentation, not a stoppered and crimped injection vial, with no sterility claim. Store at -20 degrees C plus or minus 5 degrees C, and at -80 degrees C for reference standards and stability retains, desiccated, tightly closed, under an argon or nitrogen headspace — the inert overlay is a specification, not a courtesy, because of the free Cys8 thiol, and an air-filled vial converts part of the product into its own principal degradant on the shelf. Protect from light. Hygroscopic: three arginines and a lysine make the TFA salt take up water quickly, so subdivision is performed under inert gas with the atmosphere recorded on the batch record. Equilibrate the sealed vial to ambient temperature before opening. The article is supplied dry; no reconstitution instruction is given and none appears on the label or the product page. Keep away from oxidizing agents and from transition-metal ions, which catalyze thiol oxidation. Ships ambient with a labeled cumulative excursion allowance and a single-use temperature logger in every export carton.

Shelf life

Provisional 12 months at -20 degrees C plus or minus 5 degrees C under inert headspace, from the date of QA release, stated as provisional pending the company's own stability data. That is half the 24 months carried by the plain synthetic peptides in this catalog, and it is shortened for a stated chemical reason rather than as caution: a free thiol and an oxidation-labile methionine in the same 24-mer, plus a hydrophobic Leu9-Leu12 stretch. Stability-indicating attributes: disulfide-dimer content as the primary, Met1 sulfoxide as the secondary, with aggregate by SE-HPLC, total related substances and Karl Fischer water alongside. Real-time pulls at 3, 6 and 12 months at the labeled condition plus 6 months accelerated at 40 degrees C / 75 percent relative humidity, with a headspace-integrity check at every pull because the inert overlay is part of the specification and a failed seal is the likeliest single cause of an out-of-trend dimer result. Extension beyond 12 months only on real-time data from three commercial lots. Printed retest date on every vial, first-expiry-first-out enforced against that date; material passing retest is re-dated for a further 6 months only, material failing is destroyed and the destruction is recorded.