Fmoc vs Boc SPPS

Two chemistries dominate commercial peptide synthesis. Fmoc (9-fluorenylmethyloxycarbonyl) uses milder base deprotection (piperidine) — safer, more compatible with complex sequences. Boc (tert-butyloxycarbonyl) uses strong acid (HF) for cleavage — less common now due to safety requirements. QSC uses Fmoc SPPS — the industry standard for research peptides.

Why longer peptides have lower theoretical maximum purity

Each coupling step in SPPS has ~99.5-99.9% efficiency. For a 10-residue peptide, theoretical max purity after 9 couplings = 0.999^9 = ~99.1%. For a 30-residue peptide, 0.999^29 = ~97.1%. Achieving ≥99% purity for longer peptides requires high coupling efficiency AND comprehensive preparative HPLC purification — this is why longer peptides are more expensive to produce at research grade.

Why “Qingdao” matters for peptide manufacturing

Qingdao, China is the global centre for custom peptide manufacturing — home to the highest concentration of industrial-scale SPPS facilities in the world. Suppliers with direct Qingdao manufacturing relationships can access competitive pricing without sacrificing QC if rigorous independent testing is maintained. QSC’s direct manufacture + Janoshik testing combines manufacturing efficiency with independent verification.

Why lyophilised peptide is white and fluffy

The freeze-drying process creates a highly porous, low-density matrix — the peptide cake occupies the volume previously occupied by ice crystals. This is normal and expected. A compact, glassy, or crystalline appearance might indicate incomplete lyophilisation or moisture re-absorption.

What is Fmoc SPPS and why is it the standard?

Fmoc (9-fluorenylmethyloxycarbonyl) solid phase peptide synthesis is the dominant method for manufacturing research and pharmaceutical peptides. Fmoc uses base-labile N-terminal protection and milder cleavage conditions than the older Boc chemistry — making it safer, more scalable, and compatible with a wider range of amino acid side chains.

Why do longer peptides cost more than shorter ones?

Each coupling step in SPPS has ~99.5-99.9% efficiency. For a 30-residue peptide (29 couplings), the theoretical maximum yield after synthesis is ~97%. Achieving ≥99% purity from this crude mixture requires extensive preparative HPLC — more column time, more solvent, lower recovery yield. The final cost of goods for longer peptides is substantially higher per mg than for shorter ones.

What are deletion sequences and should I be concerned?

Deletion sequences are peptides where one or more amino acids were skipped during synthesis due to incomplete coupling. They appear as earlier-eluting HPLC peaks and produce a lower MW peak in MS. At ≥99% HPLC purity, deletion sequences account for <1% of total material — below the threshold for research concern in most assay designs.

What does “lyophilised” mean on a peptide vial label?

Lyophilised means freeze-dried. The peptide was dissolved in solution after purification, frozen, then dried under vacuum (sublimation). The result is the stable dry powder in the vial. Reconstitution with bacteriostatic water re-dissolves the powder for research use.