Peptide purity requirements

What peptide purity is required for your project? Generally speaking, you will always benefit from choosing higher level of purity for your peptides. The question is whether or not this is necessary. If you can safely choose lower purity, then there is time and money to be saved. There are several factors to consider; application, QC, and overall peptide quality.

The most obvious factor, which is usually the only one that is taken into consideration, is what application your peptide is intended for. We can divide this into three rough categories; screening, non-quantitative and quantitative studies, and their corresponding typical requirements; low, medium and high peptide purity. In addition to these one often considers two special cases, polyclonal antibody production and monoclonal antibody development.

Second the quality control factor, and more precisely purity estimation by analytical HPLC. One important aspect to remember is that the results are relative. The reported purity as obtained in one HPLC system using a certain protocol is not necessarily the same as one obtained from another setup. In fact, the difference can be potentially huge. Thus, material delivered at 80% from one lab with excellent QC may in reality very well be of higher purity than material reported as 95% from a low quality vendor. We invite you to read about our views on quality control of synthetic peptides. Here it suffices to say that unless you feel confident about the QC of the peptide manufacturer then always go for the highest purity, regardless of application.

The final factor is that of the overall peptide quality. When high quality peptide synthesis reagents are used, errors like doubly added amino acids are minimized. When the synthesis strategy employs a capping cycle between each amino acid coupling step, then there are no deletion sequences. That means that done right, even the crude material prior to purification is a pretty decent peptide and certainly usable in several applications. That is nice in itself, but it is also the only route for when you need to obtain the highest levels of purity for applications where this is called for. We discuss this in some detail in our article on high quality peptide production.

Whit that said, our purity guidelines are as follows;

• Screening : low purity, desalted
  For example peptide scanning epitope mapping.
• Non-quantitative studies : medium purity, >70-80%
  For example qualitative ELISA.
• Quantitative studies : high purity, >95%
  For example NMR.

Additional information

• Net peptide content, amino acid analysis and elemental analysis
• Peptide counter ions

Innovagen has serviced the research community since 1992. In that time we have delivered numerous synthetic peptides, from libraries of screening peptides to highly purified speciality peptides. Our experience and commitment to quality and customer service are all things that you will benefit from when turning to us for your peptide requirements.