Solid-Phase Peptide Synthesis (SPPS)
All Vendors COMPP products are manufactured by Fmoc/tBu solid-phase peptide synthesis, the industry-standard method in which the C-terminal residue is anchored to an insoluble resin support and the peptide chain is assembled amino acid by amino acid in the N-terminal direction. Each cycle consists of Fmoc deprotection, activation and coupling, and washing; incomplete couplings are minimized through in-process monitoring (Kaiser/chloranil tests) and recoupling where required. The growing chain remains tethered to the resin until final cleavage in trifluoroacetic acid, which simultaneously removes side-chain protecting groups and releases the crude peptide.
For difficult sequences — long hydrophobic domains, beta-amyloid-type aggregating motifs, or heavily modified chains — we employ microwave-assisted synthesis, pseudoproline dipeptide building blocks and backbone protection strategies such as Hmb to suppress on-resin aggregation. These are the same techniques described in the peer-reviewed peptide sciences literature, and they routinely convert failed sequences into delivered projects.
Purification: Preparative Reverse-Phase HPLC
Crude peptides are purified on preparative C18 reversed-phase HPLC systems using water/acetonitrile gradients. Fraction collection is guided by UV detection at 214 nm (peptide bond absorbance) and 280 nm (aromatic residues), with analytical reinjection of each fraction before pooling. Where an application demands it, we can exchange the TFA counterion for acetate or hydrochloride, and we verify the exchange by ion chromatography. The pooled product is shell-frozen and lyophilized to yield the fluffy white solid researchers expect.
Identity and Purity Confirmation
| Method | What It Confirms |
|---|---|
| Analytical RP-HPLC | Chromatographic purity; detects deletion sequences, oxidation and hydrolysis products |
| ESI-MS or MALDI-TOF | Molecular weight; confirms the intended sequence was synthesized |
| Quantitative amino-acid analysis | Net peptide content — how much of the vial weight is actually peptide |
| UV spectroscopy | Concentration via calculated extinction coefficient for chromophore-containing peptides |
| LC-MS mapping (optional) | Sequence confirmation for critical projects and modified peptides |
Independent third-party verification is increasingly common practice in the research community — our peptide testing guide explains how labs such as Janoshik and Finnrick Peptide Testing operate and how to read their reports.
Stability, Storage and Shipping
Lyophilized peptides are stable for years at −20 °C in the dark. We ship catalog products with gel packs and custom projects frozen where the sequence demands it (methionine- and cysteine-containing sequences are the most oxidation-sensitive). Once reconstituted, peptides behave very differently from the dry state — our reconstitution guide covers bacteriostatic water versus sterile water, vial handling and fridge life of reconstituted peptides in detail.
Capability Summary
- Automated and microwave SPPS synthesizers up to multi-gram resin loads
- Preparative HPLC up to dynamic-column scale; analytical HPLC with diode-array detection
- ESI-QTOF and MALDI-TOF mass spectrometry on site
- Cleanroom vialing, lyophilization and moisture-controlled packaging
- Controlled document archive: every batch record retained for 10 years