Colivelin

What Colivelin is, structurally

Colivelin is a hybrid peptide, one chain assembled from two separately originating segments rather than a fragment cut from a single parent. One derives from ADNF, activity-dependent neurotrophic factor. The other is a shortened, substituted version of humanin, seventeen residues where the natural sequence is twenty-four, with changes at two positions.

The residue list is not recorded in the product database, so the observations below derive from the molecular formula.

The most informative thing the formula says is what it lacks: no sulfur. That matters more here than on an arbitrary peptide, because natural humanin contains a cysteine and a substituted derivative might or might not retain it. The formula settles it. Whatever the substitutions changed, no cysteine or methionine survives into the final molecule, so no disulfide can form, no free thiol exists to oxidise or dimerise, and no reducing agent is ever required.

The rest is unremarkable for this size. Thirty-two nitrogens across roughly twenty-six residues leaves only a handful of side-chain nitrogens beyond the backbone, so this is not a strongly basic chain, while thirty-five oxygens indicate a substantial contribution from acidic and hydroxyl-bearing side chains. The molecule is water soluble, though no quantitative figure is quoted here.

At around twenty-six residues this is long enough to adopt genuine secondary structure, unlike the short peptides here, which affects handling rather than identity.

Reconstitution and handling

Sterile water is the default solvent, and with no metal centre present PBS or an appropriate assay buffer are equally suitable. Add diluent slowly down the inside wall of the vial, swirl gently, and let the solution stand until it clarifies.

Do not vortex. On a chain this length that is not a formality: shear and foaming unfold and aggregate peptides long enough to have structure, and a hybrid has an interface between its segments where that can begin.

No reducing agent is needed, and adding one by reflex would be a mistake, since the molecule contains no sulfur for it to act on.

Adsorption onto plasticware is worth allowing for at low concentration, and low-protein-binding tubes reduce measured loss. A peptide of this size presents appreciably more binding surface than the tetrapeptides alongside it.

This is laboratory preparation chemistry, not dosing, administration, or protocol guidance of any kind.

Storage and stability

Store the lyophilized powder at -20 degrees C, sealed, desiccated and protected from light, and let a cold vial reach room temperature before opening. Reconstituted, hold at 2 to 8 degrees C for short-term work, or aliquot and freeze for longer storage.

Freeze-thaw discipline matters. A chain long enough to fold can misfold and aggregate on cycling, and aggregation is not reversed by warming the solution back up. Aliquot before the first freeze.

The chemical liabilities are hydrolytic rather than oxidative, since the absence of sulfur closes the oxidation routes. Any aspartate can cyclise and reopen as isoaspartate at unchanged mass, and any asparagine or glutamine can deamidate with a shift of about one unit. Without the sequence this page will not name positions, only note that a chain this length will contain candidates and that cold, near-neutral storage limits both.

These are storage conditions for the material, not dosing or administration guidance.

How Colivelin is tested

Reversed-phase HPLC establishes chromatographic purity as area percent, detected in the low UV near 214 nm where the amide bond absorbs. Whether 280 nm is usable depends on aromatic content the formula alone cannot confirm, so it should not be assumed.

Area percent is a chromatographic measure rather than peptide content by weight. Solid-phase synthesis delivers a salt, commonly trifluoroacetate or acetate, sitting outside the molecular weight above. Residual trifluoroacetate, truncated chains and deletion sequences are the classes to resolve, and on twenty-six residues a single deletion is a small proportional mass change demanding a capable separation.

Mass spectrometry confirms identity against the expected weight. The compound-specific observation is again an absence: with no sulfur there is no oxidation satellite to anticipate, so a species sixteen units above the molecular ion lacks the routine explanation it would have on a methionine-containing peptide. Aggregation, the more realistic failure mode here, is better assessed by size-exclusion chromatography, since a non-covalent aggregate dissociates under electrospray.

These describe general methodology, not a claim about any particular batch.

Handling FAQ

Does this contain a disulfide, given humanin has a cysteine? No. The molecular formula contains no sulfur at all, which settles it regardless of what the parent sequence carries. Whatever the substitutions changed, no cysteine survives into this molecule, so no disulfide is possible and no reducing agent is needed.

Why does size-exclusion chromatography get a mention when mass spectrometry is available? Because the likely failure mode for a chain this long is non-covalent aggregation, and that does not survive electrospray ionisation. Mass spectrometry would report a normal monomer while an aggregated sample sat in the vial. Size exclusion sees the aggregate directly.

Full specifications for Colivelin.