Peptide Purity and Content
Peptide purity, measured by analytical reversed phase HPLC, is the percentage of the peptide compared to impurities that absorb at 210-220 nm, (peptide bond absorption wavelength). Impurities consist of deletion sequences, incompletely deprotected sequences, truncated sequences and side products of the synthesis process. Residual salt and water that do not absorb at this wavelength are not quantified. In experimental planning it is important to consider that some peptide or non-peptide impurities may be toxic to cells. This can generally be avoided by purifying the peptide, which will result in only trace amounts of toxic impurities.
Recommended purity based on application of peptide
Lyophilized peptides contain impurities in the form of counterions and residual water. Net peptide content, measured by amino acid analysis, is the percentage of all peptides relative to these non-peptide impurities. It varies according to the purification and lyophilization procedures, and is affected by the amino acid composition, particularly the presence of hydrophilic amino acids in the sequence.
Peptide purity and net peptide content are the major factors affecting variability between batches of peptides. The lower the purity, the greater will be the variability between batches synthesized. Once the peptide has been solubilized, measure the peptide concentration in solution in order to be able to compare peptide activity in experimental assays between batches.
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