Introduction
Many types of research require peptides from over 100 to up to 150 amino acids. The challenge in the synthesis of such long peptide is to overcome the enormous cumulative effect of the yield. Synthetic inefficiencies associated with peptide aggregation, such as slow or incomplete coupling and/or deprotection reactions, illustrate the complexity that often arises. A second issue in long peptide synthesis is poor solvation during assembly of the protected peptide.
For successful long polypeptide synthesis, it is essential to overcome the aforementioned problems, for which multiple of strategies have been described and are applied by Kirkland Peptide. These include high-swelling resins with low peptide loadings, pseudoproline building blocks, fragment condensation, native chemical ligation and others.
Kirkland Peptide scientists will thoroughly evaluate the target peptide sequence, and select the most promising synthetic approach. Over time, Kirkland Peptide has obtained a lot of experience in the successful synthesis of challenging long peptides, and developed these into well documented protocols. These ensure a high success rate, even for peptides with lengths of up to 100 amino acids or more.
For long peptides, Kirkland Peptide frequently makes use of fragment synthesis and chemical ligation technologies, by which the unprotected peptide chains react chemo-selectively in aqueous solution. The most common form of chemical ligation involves a peptide thioester that reacts with a terminal cysteine residue. This synthesis strategy is routinely implemented within our synthesis platform, and allows to successful long polypeptide synthesis.
Long Peptide Synthesis SPPS Strategy
We are asked frequently to synthesize relatively large peptides sized 100–150 residues, which is the size of a mean protein domain. We recently synthesized a 130+amino acid peptide. This demonstrates that the synthesis of peptides sized 100–200 amino acids is not beyond the capabilities of our ligation 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.
