Long peptide synthesis requires careful control of aggregation, incomplete coupling and purification. ChinaPeptides has established methods for sequences approaching 150 amino acids.
Projects may use optimized SPPS, fragment condensation or hybrid strategies depending on sequence composition.
Length alone is not the only difficulty. A 35-residue hydrophobic stretch can fail more readily than a 60-residue polar sequence. The inquiry should include known problematic motifs, desired purity and whether a fragment junction is acceptable.
Yield falls as length increases. We will state when a requested purity and quantity combination is unlikely without a route change.