DNSP-11

What DNSP-11 is, structurally

DNSP-11 is a peptide of eleven residues whose sequence ends in NH2, and the formula confirms that ending rather than repeating it. The same chain finishing in a free acid would compute to C50H80N14O19; the formula on file is C50H81N15O18, one nitrogen more and one oxygen fewer, exactly the exchange of an amide for a hydroxyl. Summing standard atomic weights across it gives 1180.29 against the 1,180.27 on file, agreeing within rounding.

The sequence sits inside a larger protein, proGDNF, but a fragment and its parent are different substances: this molecule weighs a little over eleven hundred daltons and the precursor protein many times that. Shared sequence does not make two materials interchangeable.

Composition follows from backbone accounting. Eleven residues give eleven amide nitrogens and the terminal amide a twelfth, leaving three of the fifteen on side chains, while eleven carbonyl oxygens leave seven of the eighteen. The three nitrogens all belong to one arginine; the oxygens sit on two glutamates, an aspartate and a serine hydroxyl. Three carboxylic acids against one guanidinium, and no terminal carboxylate, give a net negative charge at neutral pH and an isoelectric point around 4.3.

That fixes the direction of the dissolution advice, reversing what a basic peptide wants: lowering the pH moves this peptide toward its isoelectric point, where net charge is zero and solubility is minimal, so dilute acetic acid makes a stubborn vial worse.

The formula holds no sulfur, so there is no disulfide to reduce or scramble, no free thiol to dimerise in air, and no methionine to oxidise. Three of the eleven residues are prolines, two adjacent at the N-terminus, restricting the backbone and letting each proline sit cis or trans. No tryptophan, tyrosine or phenylalanine is present.

Reconstitution and handling

Sterile water is the default solvent, with phosphate-buffered saline or an assay buffer as alternatives, there being no metal centre for phosphate or a chelator to disturb. Add diluent slowly down the vial wall, swirl gently, and let it clarify. Do not vortex, which only introduces foam. No reducing agent is needed, there being no disulfide.

Where a vial is slow to dissolve, the escalation is upward in pH. Dilute ammonium hydroxide or ammonium bicarbonate raises the net negative charge, and both are volatile enough to be stripped later by lyophilisation. Acid is the wrong direction.

Adsorptive loss deserves attention at low working concentrations. A net negative molecule binds borosilicate glass less readily than a basic peptide would, that surface being negative too, so polypropylene is the greater concern; low-protein-binding tubes help.

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 or below, sealed, dry and dark, and let a cold vial reach room temperature before opening so moisture does not condense on the solid. Reconstituted, hold at 2 to 8 degrees C, or aliquot and freeze so the material thaws once.

Two common peptide liabilities are absent: no asparagine or glutamine, so no deamidation, and no sulfur, so no oxidation. What remains is the aspartate, which can cyclise to a succinimide and reopen as isoaspartate, an isomer of identical mass that a mass check cannot detect. That reaction needs the backbone nitrogen of the following residue, so position decides whether it can happen: the aspartate is eighth of eleven, not terminal, and followed by an arginine with an ordinary backbone NH. Cold storage is the control.

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

How DNSP-11 is tested

Reversed-phase HPLC establishes purity as area percent and mass spectrometry confirms identity against the nominal 1,180.27. Area percent is a chromatographic measure rather than peptide content by weight, and residual trifluoroacetate from cleavage is part of what the vial weighs.

Lacking aromatic residues, detection sits at 214 or 220 nanometres, where the peptide bond absorbs, rather than at 280. Because each of the three prolines can adopt a cis or trans amide bond, the peak may broaden, shoulder or split with no second substance present, so asymmetry is not automatically an impurity.

A carboxy-terminal amide is one dalton lighter than the free acid, so a mass near 1181.3 rather than 1180.3 indicates the acid form. Truncation and deletion products are the other class separated, and the adjacent N-terminal prolines are where to expect them.

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

Handling FAQ

The vial is slow to dissolve. Should a little acid be added? No. That suits a basic peptide, not this one. Three acidic side chains against a single arginine put the isoelectric point low, so acid drives the peptide toward minimum solubility. Raise the pH instead.

Can concentration be checked by absorbance at 280 nanometres? No. There is no tryptophan, tyrosine or phenylalanine, so nothing absorbs there. Use 214 nanometres, amino acid analysis, or gravimetry corrected for salt and water.

Full specifications for DNSP-11.