Quality & purity

Why >99% matters

The difference between a 98% pure peptide and a >99% pure peptide is not 1%. It is the difference between an experiment whose readout reflects your variable of interest and an experiment whose readout is muddied by 2% of unknown side-products. For research peptides at low working concentrations, those side-products can be biologically active in their own right. We do not release lots below 99% — full stop.

Stage 1 — synthesis

Solid-phase peptide synthesis (SPPS) using Fmoc chemistry, performed on a Wang or Rink-amide resin depending on the C-terminal chemistry required. Each coupling cycle uses HBTU / HOBt activation and is monitored by colorimetric ninhydrin assay; failed couplings are re-coupled before deprotection of the next residue. Side-chain protecting groups follow standard Fmoc orthogonality.

Stage 2 — cleavage and crude

Final cleavage from the resin uses a TFA-based cocktail with appropriate scavengers (water, TIS, EDT depending on residue content). The crude peptide is precipitated into cold ether, centrifuged and dried.

Stage 3 — preparative HPLC

Crude peptide is purified on a preparative reverse-phase C18 column under a water/acetonitrile gradient with 0.1% TFA. The fractions corresponding to the target retention time are collected, pooled, and analyzed by analytical HPLC. If the pooled material is <99% pure, it is re-purified.

Stage 4 — counterion exchange

For most peptides the TFA counterion is exchanged for acetate by lyophilizing from a 10% acetic acid solution two to three times. This is the standard salt form expected by research labs and minimizes TFA-related cell-culture artifacts.

Stage 5 — analytical release

Two analytical methods are required for release:

• RP-HPLC — typically a C18, 4.6 × 250 mm column, 1 mL/min, 5–95% acetonitrile gradient over 30 minutes, dual-wavelength detection at 214 and 280 nm. Target peak area must be >99.0% of total integrated area.
• LC-ESI-MS — observed monoisotopic mass must match the theoretical mass within 0.5 Da.

Stage 6 — fill, freeze, lyophilize

Material is dissolved in a small volume of water, sterile-filtered through a 0.22 µm membrane, dispensed into glass vials, shell-frozen at -40°C, and lyophilized for 24–48 hours under high vacuum. Vials are stoppered under inert atmosphere before being crimp-sealed.

Stage 7 — lot release & COA generation

A unique lot number is assigned. The COA — chromatogram, MS spectrum, weights, dates, signatures — is filed and is available to any customer of that lot on request.

What can still go wrong

• Storage breakdown — once the vial leaves our cold-chain it is on you. See the storage guide.
• Reconstitution shear — shaking the vial denatures certain peptides. Always swirl. See the reconstitution guide.
• Solvent incompatibility — some hydrophobic sequences need a small amount of acetic acid or DMSO before dilution into water.