MIF-1

1 Identity

Synthetic tripeptide, all-L, entirely proteinogenic, with an obligatory C-terminal primary amide. Constitutionally identical to a described endogenous human tripeptide. The name comes from a 1970s hypothesis and is used here only as a name. Not synonyms and each a different article: MIF (macrophage migration inhibitory factor), a recombinant protein; Tyr-MIF-1, a separate tetrapeptide; and nemifitide, a pentapeptide analog.

Sequence

H-Pro-Leu-Gly-NH2; one-letter PLG with an obligatory C-terminal primary amide, three residues. All-L, entirely proteinogenic. Free N-terminal secondary amine on proline - note that the N-terminus is a secondary amine, not a primary one, which changes derivatization chemistry and Edman behavior and is worth stating rather than assuming. No acetylation, no acylation, no lipidation, no disulfide (there is no cysteine), no non-proteinogenic residue, no D-residue. No ionizable side chain at all: there is no Lys, Arg, His, Asp or Glu in this sequence, so the only protonatable site is the N-terminal proline amine and the article is a mono-salt - a certificate claiming di- or tri-salt stoichiometry is arithmetically wrong before it is analytically wrong. No aromatic residue either, so 280 nm is not a valid detection wavelength and purity must be reported at 210-214 nm. The C-terminal amide is part of the identity, not A finishing detail: the free acid Pro-Leu-Gly-OH is a different article 0.98 Da heavier and is a named, limited impurity here.

Molecular formula

C13H24N4O3 (C-terminal amide, the specified article). Free acid Pro-Leu-Gly-OH C13H23N3O4. Mono-acetate C15H28N4O5; mono-trifluoroacetate C15H25F3N4O5. Governing degradant cyclo(Pro-Leu) C11H18N2O2 with co-released glycinamide C2H6N2O. Tyr-MIF-1 C22H33N5O5.

Average mass

284.36 Da (C13H24N4O3); the formula on IUPAC 2021 abridged conventional atomic weights gives 284.360. Comparators, each from its stated formula: free acid Pro-Leu-Gly-OH 285.34 (+0.98); mono-acetate 344.41, of which 17.4 percent of the gross weight is acetate; mono-trifluoroacetate 398.38, of which 28.6 percent is trifluoroacetate - on a 284 Da tripeptide a single trifluoroacetate counterion is more than a quarter of the vial, so a 10 mg gross fill of the trifluoroacetate contains about 7.1 mg of peptide. Degradants: cyclo(Pro-Leu) 210.28; glycinamide 74.08. Tyr-MIF-1 447.54.

Monoisotopic mass

284.18484 Da neutral (C13H24N4O3). [M+H]+ 285.19212; [M+Na]+ 307.17406; [M-H]- 283.17756. Free acid 285.16886 neutral, [M+H]+ 286.17614 - note that the free acid's [M+H]+ at 286.176 and the amide's [M+Na]+ at 307.174 are both routinely mis-assigned on low-resolution instruments, so the adduct must be named on the certificate. Cyclo(Pro-Leu) 210.13683. Tyr-MIF-1 447.24817. All values follow from the stated formulas.

Salt / variant note

(1) the acronym collision, which is the largest single risk on this record: MIF - macrophage migration inhibitory factor - is a 114-residue recombinant protein of roughly 12.5 kDa, sold by the same institutional catalog houses, differing from this article's name by one digit and from its mass by a factor of forty-four. A purchase order reading 'MIF' has ordered a protein; a purchase order reading 'MIF-1' has ordered a tripeptide; and a shipment of the wrong one is caught instantly by mass and not at all by name. (2) free acid Pro-Leu-Gly-OH, C13H23N3O4, 285.34 / 285.16886 - +0.98 Da, and the routine incomplete-amidation or hydrolysis failure. (3) TYR-MIF-1, Tyr-Pro-Leu-Gly-NH2, C22H33N5O5, 447.54 / 447.24817 - +163.18 Da, a distinct and separately cataloged tetrapeptide from the same literature, and the article a buyer receives when a supplier reads 'MIF-1' as a family name. (4) NEMIFITIDE, a pentapeptide analog from the same development program, sold under its own INN - named here without a mass, because no formula for it was checked against a primary source, and no mass is printed here that is not tied to a formula that was checked. (5) sequence permutations: LPG, GLP, PGL, LGP and GPL all share the formula C13H24N4O3 and are isobaric with the target to every decimal place; only MS/MS b/y sequencing separates them, and with a three-residue amide the informative fragment set is small, which is why co-elution against a characterized reference standard is required alongside it. (6) EPIMERS: [D-Pro1]-, [D-Leu2]- and the doubly epimerized forms are all exactly isobaric and co-elute on achiral reversed-phase columns; [D-Pro]-MIF-1 in particular is a described research compound and is therefore a purchasable substitution route rather than a theoretical one. (7) governing degradant cyclo(Pro-Leu), C11H18N2O2, 210.28 / 210.13683, formed by N-terminal diketopiperazine cyclization with loss of glycinamide (74.08) - a Pro-Leu N-terminus is one of the most cyclization-prone motifs in peptide chemistry and this is the stability story for the article. (8) Salt forms: mono-acetate 344.41 and mono-trifluoroacetate 398.38, the latter more than a quarter counterion by mass.

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.

What exists, by study type. Primary neuroendocrine and peptide-chemistry literature dating to the early 1970s, in which the tripeptide was isolated, sequenced and synthesized, and from which its historical name derives. A substantial rodent behavioral-pharmacology and receptor-binding literature through the 1970s to 1990s. Analytical and peptide-chemistry literature on the stability of Pro-Leu-Gly-NH2 in solution, which is directly relevant to the specification above and is the most useful part of the file for a catalog record. A small early human-study literature exists from the same period, generally uncontrolled or small-crossover in design; a separate later program carried a pentapeptide analog, nemifitide, into registered early-phase human study, and that analog is a different molecule whose trial record does not transfer to this one. No modern registered controlled human trial of the tripeptide itself was identified. Identifiers are not individually re-verified here; the point is the shape of the published literature, and no statement is made about what the compound does - including no statement derived from the expansion of its own acronym.

4 Storage & specification

Storage

White lyophilized or crystalline powder, acetate salt, in a screw-cap amber borosilicate vial with a PTFE-lined closure; a laboratory-chemical presentation, non-sterile, with no sterility claim. Store at -20 degrees C plus or minus 5 degrees C, tightly closed and desiccated, protected from light. Moisture control is the operative requirement and it is specific rather than general: a Pro-Leu N-terminus is among the most diketopiperazine-prone motifs in peptide chemistry, the cyclization is hydrolytically and thermally accelerated, and it is the reaction that will define this article's shelf life. A desiccant sachet travels in the secondary pack, the label carries a close-immediately-after-weighing instruction, and the sealed vial is equilibrated to ambient temperature before opening so that atmospheric moisture does not condense onto the cake. With only one basic site the salt is less hygroscopic than most tripeptides in this catalog, which is a reason to specify the acetate rather than the trifluoroacetate and not a reason to relax the desiccant condition.

Shelf life

Provisional retest interval 24 months from QA release at -20 degrees C plus or minus 5 degrees C, desiccated, stated as provisional pending the company's own stability data, with A mandatory 3-month first pull on each of the first three commercial lots rather than the 6-month first pull used elsewhere in this catalog. The reason is the Pro-Leu diketopiperazine: it is the fastest-forming degradant, an early pull is what tells the company whether 24 months is defensible at all, and a first data point at six months on a fast reaction is a data point taken too late. Protocol ICH Q1A(R2)-style: pulls at 0, 3, 6, 9, 12, 18 and 24 months at the labeled condition, plus 6 months accelerated at 40 degrees C / 75 percent relative humidity, with cyclo(Pro-Leu) and free glycinamide reported individually at every pull rather than pooled into total related substances. If the accelerated arm shows diketopiperazine growth above 0.5 percentage points absolute, the routine interval is cut to 12 months and the labeled condition moves to -80 degrees C before any extension is considered. Retest date printed on every vial; first-expiry-first-out enforced against that date.