Catalytic active sites and most receptor binding sites for small ligands are found at domain and subunit interfaces. Long peptides are frequently synthesized to study the protein-receptor binding. Two active sites are indicated by the presence of the bound ligands (yellow). Both sites are at an interface between the two subunits of the protein.

We are asked frequently to synthesize relatively large peptides sized 100–200 residues, which is the size of a mean protein domain. We recently synthesized a 169-amino acid peptide. This demonstrates that the synthesis of peptides sized 100–200 amino acids is not beyond the capabilities of our current PeptideSyn technology. This long peptide was synthesized from intermediate fragments that were generated using stepwise SPPS, purified in their unprotected form, and ligated chemically with minimal protection.

A Simple Protocol to Refold Peptides or Small Proteins.

Obtaining peptides sized 100–200 amino acids using chemical synthesis is much faster and cheaper than cloning and overexpressing in Escherichia coli. In addition, the resulting peptide is always correct. Chemical synthesis can be used to incorporate non-genetically encoded structures, such as D-amino acids, into the protein in a completely regular fashion. Synthetic peptides eliminate problems such as poor or no expression, cloning errors, tags like FLAG or 6-His, or the mis-translation of non-preferred codons in prokaryotic hosts. Artificial amino acids that have isosteric side chains can be used to investigate the functional importance of specific residues.

Strategy for Synthesis-Solid Phase and hybrid technology

• Rapid synthesis of long peptides using an Fmoc/Boc strategy
• Short production cycles
• Automated and scalable procedure
• No isolation of intermediates

• Expensive raw materials, waste and operation
• Complex impurity profiles that include inserted, truncated, deleted, double-hit, modified, and unmodified amino acids
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