Peptide YY (PYY 3-36)

What PYY 3-36 is, structurally

Peptide YY (PYY 3-36) is a peptide of thirty-four residues weighing 4049.52 g/mol, near the practical ceiling for routine solid-phase synthesis.

The name records the relationship to the full-length parent, PYY 1-36, and it is one of identity, not degree. This is the parent chain with its first two residues absent, a different substance of a different mass, roughly two hundred and sixty units lighter.

The formula is the more informative half of the data block, because C180H279N53O54 carries no sulfur. Across thirty-four residues that absence closes a whole branch of peptide chemistry. No cysteine means no disulfide to form, reduce or scramble. No free thiol means no oxidative dimerisation in air. No methionine means the sixteen-unit sulfoxide that dominates storage advice for peptides this size cannot arise.

The rest divides by arithmetic, though not on the first attempt. Thirty-four residues carry thirty-four backbone nitrogens, one per residue counting the free N-terminal amine, apparently leaving nineteen on side chains, and thirty-five backbone oxygens if the chain ends in a free acid, leaving nineteen again. That reading fails against the total. A thirty-four residue free acid computes to C180H278N52O55, whereas the supplied formula sits one hydrogen and one nitrogen above and one oxygen below it, exactly the free acid to primary amide difference. The C-terminus is therefore amidated, and the corrected split is eighteen side-chain nitrogens against twenty side-chain oxygens. Since the database does not state the amidation, read both sets as approximations.

Eighteen against twenty is balanced, which excludes the extremes without identifying the residues. One arginine carries three side-chain nitrogens and one glutamate two side-chain oxygens, so the same totals assemble from very different compositions. Expect a modest net charge near neutral pH, and no confident steer on which way a pH shift moves solubility.

Reconstitution and handling

Sterile water is the default solvent, and phosphate-buffered saline or an assay buffer are equally reasonable, as this is not a metal complex. Add diluent slowly down the inside wall of the vial, swirl gently, and let the solution clarify. Do not vortex. No reducing agent is needed, there being no disulfide for one to act on.

Where a vial dissolves reluctantly, resist reaching for acid by reflex. Dilute acetic acid is the reliable escalation on a strongly basic peptide, but a balanced composition offers no such assurance: a pH shift can approach the isoelectric point as easily as retreat from it. Warmth and time are safer.

Adsorption matters at the low concentrations these solutions are usually made to. A four kilodalton peptide binds readily to ordinary polypropylene, and low-protein-binding tubes reduce the measured loss.

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 so moisture does not condense onto the powder. Reconstituted, hold at 2 to 8 degrees C, or aliquot and freeze rather than thawing one vial repeatedly.

The liabilities are hydrolytic rather than oxidative, sulfur chemistry being off the table. The C-terminal amide follows directly from the formula: it can hydrolyse back to the free acid, one unit heavier and easy to miss at this size. Twenty side-chain oxygens indicate acidic and hydroxyl residues, and aspartate carries the usual succinimide route to isoaspartate. That route needs the backbone nitrogen of the following residue, so it is closed at the final position and blocked before any proline. With no sequence on file this page names no positions.

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

How PYY 3-36 is tested

Reversed-phase HPLC establishes chromatographic purity as area percent. At thirty-four residues the impurities that matter are truncation and deletion sequences, which can elute close to the target.

Area percent is not peptide content by weight. Solid-phase synthesis delivers a salt, commonly the trifluoroacetate, and the counter-ion is a real share of the vial contents, so a certificate should state the salt form.

Mass spectrometry confirms identity against 4049.52, with two points specific to this size. Average and monoisotopic mass diverge by about two and a half units at four kilodaltons, so a reported figure must say which convention it uses. Electrospray returns a multiply charged envelope rather than a single ion, so the quoted mass is a deconvolution result. There is no sulfoxide to chase.

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

Handling FAQ

Is this the same compound as PYY 1-36? No. They are separate products. This is the thirty-four residue chain; PYY 1-36 is the thirty-six residue parent, roughly two hundred and sixty units heavier and readily separated by mass.

The powder dissolved slowly. Should I add acid? Not as a first step. Acid is the right escalation for a strongly basic peptide, and this composition is balanced, so a pH drop may approach the least soluble point rather than retreat from it. Warm the vial and allow more time first.

Full specifications for Peptide YY (PYY 3-36).