Peptide Production 

This affects not only the ease of assembly of amino acids, but also solubility, stability and the later purification process.

Most peptides of interest, such as those used as antigens, proceed from N-term ends, C-term or from the interior of a sequence of native proteins.Thus these peptides are not always ideal.

Some can be insoluble or unstable, others can cause purification problems, whilst, in other cases, folding may not be similar to that of native proteins.

Thanks to the experience we have acquired over the years, at Immunostep  we can locate those problematic amino acids and modify them by improving the qualities of synthesised peptides.

Several different modifications can be made during production according to our customers’ needs, for example covering N-term or C-term regions, as required, carrying out chemical modifications, inserting spacers, or replacing “problematic” amino acids.

One of the most critical factors in synthesis and purification is excessive length. For instance, at Immunostep we recommend never exceeding 10-15 amino acids for peptides used as antigens, since they will be ideal as they maintain the structure of the linear epitope in native proteins. 

Hydrophobicity affects peptide solubility considerably; in this sense, our experience allows us to increase peptide solubility by adapting the frequency of the different amino acids depending on their hydrophilic and/or hydrophobic characteristics.

High incidence peptides such as tryptophan, leucine, valine, methionine, phenylalanine, isoleucine may not dissolve in aqueous solutions, and this allows us to maintain the ratio of these hydrophobic amino acids below 50% while securing the existence of at least one charged amino acid per five residues.

At physiological pH, arginine, glutamine, aspartic acid and lysine are charged on their side chains. One simple change or the elimination of some polar residues at the N-term or C-term ends may influence solubility either positively or negatively.

During the process of peptide synthesis, the formation of β sheets may affect the solvation and ordered synthesis of the peptide, causing losses in its different zones.

We can reduce the number of these deletions and the appearance of unwanted products in the synthesis by recommending the elimination of zones in which there are multiple or adjacent residues of valine, isoleucine, tyrosine, phenylalanine, tryptophan, leucine, glutamine or threonine. In most cases, conservative changes, as well as other measures applied during synthesis can improve chances of success with regard to purity and quality.

Measures such as the insertion of glycine or proline, every three residues, or the replacement of glutamine for asparagine, or threonine for serine.