Peptide Synthesis: What Level of purity do you need?

Peptide purification is indeed necessary to get quality peptides for research. Most of the peptide synthesis services purify the products using reverse-phase high-performance liquid chromatography (HPCL). However, sometimes some other methods like ion exchange or gel filtration chromatography too are used. Custom peptides that are difficult to produce will require special services.

When placing an order for synthesized peptides it is obvious that customers request the highest purity that peptide synthesis service offers. It is always better to use reagents that are free from impurities. However, sometimes using the less pure sample is effective in cost terms for those experiments which don’t require ultra-pure peptides. Peptide synthesis service providers almost invariably offer more than three levels of purity labeled as X%. What are the differences and what purities are best in various experiments?

Lower levels of purity

Generally, the level of purity in the lower level cases ranges within >50% to 70%, with an average of about >60% purity. Peptides on this level of purity are referred to as ‘crude’ or ‘desalted’ peptides. Although the name may raise your eyebrows, this purity level can serve a useful purpose and saves you money. Desalted peptides are appropriate and useful for high-throughput screenings of large numbers of peptide for the generation of leads in pharmaceutical development, for example, as well as in other applications.

A >70% pure peptide preparation, which may contain a mixture of peptides that closely resemble one another, is very likely to generate an immune response that will result in the antibody. However, it cannot be ignored that for impurities at this level to cause unwanted effects in the animal or even some degree of toxicity. This can be caused by organic impurities remaining in the peptide preparation after the process of peptide synthesis. If this is a problem, it might be possible to extract the offending impurities from the >70% peptide preparation instead of buying a higher purity (and possibly more expensive) preparation of the peptide.

Mid-range levels of purity

In analytical applications many uses of mid-range peptide purities which comes into the range of >70% to >80% purity level. This kind of purity level is appropriate for the production, purification, and testing of antibodies. These are also referred to as ELISAs (Enzyme substrate studies) epitope mapping, affinity purification, bioassays or other immunological application and peptide screening.

Peptide purified to the >85% level are suitable for biochemistry and semi-quantitative applications, such as enzymology, tests for biological activity and epitope mapping. There are other examples of applications at this level which includes semi-quantitative studies of enzyme-substrate interactions, phosphorylation, peptide blocking in Western blotting and cell attachment.

Higher levels of purity

The higher levels of >90% to >98% purity are designed for particular applications. This level is the most expensive, and it usually isn’t necessary for the applications described above. Peptides purified to the >90% to >95% level are best for quantitative bioassays, quantitative in vitro receptor-ligand interaction studies, biological activity with ligand binding studies, quantitative blocking and competitive inhibition assays, quantitative phosphorylation and proteolysis studies, electrophoresis markers and chromatography standards.

Usually, the highest level of >98% purity is reserved for in vivo studies, clinical trials, drug studies that use peptides as pharmaceuticals and structure-activity relationship studies. This level is also best for examining protein structure by nuclear magnetic resonance studies or protein crystallography (though these latter three applications also can be accomplished using the >95% purity preparation).

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