Solid-phase peptide synthesis (SPPS), developed by Robert Bruce Merrifield in the 1960s (Nobel Prize 1984), remains the primary method for producing research peptides. Understanding the process helps researchers evaluate supplier quality claims.
The Merrifield Method
SPPS builds peptide chains on an insoluble resin support. Amino acids are added sequentially from C-terminus to N-terminus, with protecting groups preventing unwanted reactions. Each coupling cycle adds one amino acid.
Fmoc vs Boc Chemistry
Modern SPPS primarily uses Fmoc (9-fluorenylmethyloxycarbonyl) chemistry, which allows for milder cleavage conditions than the older Boc (tert-butyloxycarbonyl) approach. Fmoc chemistry is compatible with a wider range of amino acid derivatives and side-chain protecting groups.
Sources of Impurity
Common SPPS impurities include: deletion sequences (missed couplings), insertion sequences, racemized amino acids, incomplete deprotection, and residual reagents. HPLC purification removes most of these, but synthesis quality directly affects achievable purity.
Quality Indicators
High-quality SPPS uses: pharmaceutical-grade amino acid derivatives, fresh resin, inert atmosphere where required, and HPLC monitoring at each stage. The difference between 95% and 99% purity often comes down to synthesis conditions, not just purification.
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