Amylin

1 Identity

Synthetic 37-residue peptide hormone, disulfide-closed and C-terminally amidated; amyloidogenic

Sequence

Lys-Cys-Asn-Thr-Ala-Thr-Cys-Ala-Thr-Gln-Arg-Leu-Ala-Asn-Phe-Leu-Val-His-Ser-Ser-Asn-Asn-Phe-Gly-Ala-Ile-Leu-Ser-Ser-Thr-Asn-Val-Gly-Ser-Asn-Thr-Tyr-NH2; one-letter KCNTATCATQRLANFLVHSSNNFGAILSSTNVGSNTY-NH2. Thirty-seven residues, all L, closed by a Cys2-Cys7 disulfide and terminating in a C-terminal tyrosine amide. The material sold under this name is chemically synthesized, not isolated from tissue, and is normally supplied as the trifluoroacetate salt.

Molecular formula

C165H261N51O55S2 (free base, C-terminal amide, disulfide-closed)

Average mass

3903.325 Da (C165H261N51O55S2). Listings commonly print the rounded 3903.33.

Monoisotopic mass

3900.86355 Da; listings commonly print the rounded 3900.8636. [M+H]+ 3901.8708; [M+3H]3+ 1301.2971; [M+4H]4+ 976.2255.

Salt / variant note

(1) the species substitution is the dangerous one because the gap is small relative to the molecule. Rat and mouse amylin - differing at six positions including prolines at 25, 28 and 29 - is C167H272N52O53S2, 3920.44 average / 3917.9629 monoisotopic: only 17.12 Da heavier on a 3.9 kDa peptide, a difference of 0.44%. An LC-HRMS method at plus or minus 5 ppm resolves it trivially; a certificate stating '3903 plus or minus 5 Da', or the far more common 'consistent with theoretical' with no tolerance at all, does not - and 17 Da is close enough to plus 16 (oxidation) and plus 18 (hydrolysis) that an analyst working from habit will explain it away rather than investigate it. Rodent-sequence substitution is invisible to a purity number and is caught only by a full peptide map against the human sequence. (2) Pramlintide, the approved analog, is the human sequence with prolines at 25, 28 and 29: C171H267N51O53S2, 3949.44 / 3946.9207, 46.12 Da heavier. Supplying it under the amylin name converts an analytical problem into an unapproved-new-drug problem. (3) The des-amido free acid, C165H260N50O56S2, 3904.31 / 3901.8476 - exactly 0.98 Da heavier and inside any whole-dalton tolerance. Note that one catalog house's published 3904.5 sits nearer this species than another's 3903.33, and a buyer holding two certificates from two catalog houses has a 1.17 Da inconsistency to reconcile before either is trusted. (4) The reduced free-thiol form with the Cys2-Cys7 bridge open, C165H263N51O55S2, 3905.34 / 3902.8792, 2.02 Da heavier. (5) Amylin(8-37), the fragment, amidated: C138H216N42O45, 3183.50 / 3181.5905 - 719.83 Da lighter, and it contains no cysteine at all, so a free-thiol assay on it reads zero and a disulfide map has nothing to find; the free-acid form of the same fragment is C138H215N41O46, 3184.48 / 3182.5745. (6) the channel substitution that shows up in the search results rather than in the vial: searches for amylin in the consumer research-chemical channel return cagrilintide, a long-acting analog, rather than amylin itself - a different molecule with a fatty-acid side chain and a substantially different mass, sold as 'amylin analog' at 5 mg. (7) the attribute no mass and no purity number addresses: the human sequence is amyloidogenic and forms fibrils in aqueous solution. Fibrillar and monomeric material are the same molecule, the same formula and the same mass; they are different articles to a buyer, and the difference is invisible to every chromatographic test on a normal certificate.

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.

A very large in-vitro biophysical literature on fibril formation and nucleation kinetics, and a substantial rodent endocrinology literature. The human clinical record in this class belongs to the approved analog pramlintide and not to the native hormone, and transferring it across would be exactly the substitution this catalog refuses to make. No controlled human trial of synthetic native human amylin as a supplied article was identified. Where a citation index page exists for an excluded record, it separates the biophysics from the endocrinology and states that the clinical citations belong to a different molecule.

4 Storage & specification

Storage

The honest condition is -80 degrees C plus or minus 10 degrees C, lyophilized, in Type I amber glass under nitrogen, in single-use aliquots with no freeze-thaw, protected from light and moisture, reconstituted in a stated solvent immediately before use and not stored after reconstitution at all. That last clause is the problem: fibril formation proceeds in aqueous solution, so post-reconstitution storage is not a condition this company could specify or a buyer could rely on. No vial is filled and no label is printed.

Shelf life

None assigned, and the omission is substantive rather than procedural. No retest interval for synthetic human amylin can be defended from a chromatographic purity result, because the attribute that changes over time is aggregation state and the sample preparation for RP-HPLC dissolves the evidence of it. Defending an interval would require a validated physical-form method, real-time data at the labeled temperature, and an acceptance criterion on fibrillar content - none of which exists in this channel, and none of which the company will build for a class it has excluded.