MOTS-c Reference

Reconstitution and handling

Sterile water is the default solvent, and with no metal center 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 clarify. Do not vortex.

No reducing agent is required or appropriate. There is no disulfide and no free thiol, so a reducing agent has nothing to act on and only adds a reactive species to the preparation.

Limit air exposure and work in subdued light. With two methionines and a tryptophan, three separate residues are vulnerable to oxidation and one is additionally photosensitive, so both precautions are specific rather than generic.

Adsorption is worth allowing for at low concentration, with low-protein-binding tubes reducing measured loss. Four positive charges make untreated glass a likelier route than polypropylene, though four aromatic rings give a hydrophobic route too.

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 warm before opening. Reconstituted, hold at 2 to 8 degrees C, or aliquot and freeze rather than thawing repeatedly.

Oxidation dominates, and unusually there are three sites rather than one. Both methionines oxidize to sulfoxides and the tryptophan indole oxidizes independently. Air, light and trace metals drive all three, light mattering most for the tryptophan.

A second, slower route is deamidation of the glutamine at position four, which converts a neutral side chain to an acidic one and adds about one mass unit. It needs water, so the solid is protected while solutions are not, and it accelerates with warmth and alkaline pH.

Nothing else competes. There is no cysteine, so no thiol chemistry and no dimerization, and no aspartate, so no isomerization.

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

How MOTS-c is tested

Reversed-phase HPLC establishes chromatographic purity as area percent. Four aromatic rings, including a tryptophan, make 280 nm a genuinely strong detection channel alongside the low-UV amide measurement at 214 nm.

Area percent is a chromatographic measure rather than peptide content by weight. Solid-phase synthesis delivers a salt, commonly trifluoroacetate or acetate, and with four basic side chains the counter-ion load on this peptide is high.

Mass spectrometry confirms identity, and the oxidation signature needs more care than on a single-site peptide. Three residues can each take up oxygen, so oxidized material appears above the molecular ion at sixteen for each methionine sulfoxide and at four, sixteen or thirty-two for the tryptophan depending on which product forms, which means the satellites are not confined to multiples of sixteen and a plus-sixteen peak does not say which site was hit. Localizing it requires fragmentation. On most peptides that satellite has one obvious explanation; here it has three.

Deamidation of the glutamine adds about one mass unit, which on a molecule of 2175 sits within the parent's isotope envelope and needs adequate resolving power to separate.

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