Estimation of peptide concentration by a modified BCA assay

Although biuret based protein assays are theoretically applicable to peptide measurement, there is a high level of inter-peptide variation, determined largely by peptide hydrophobicity. This variation in peptide reactivity can be significantly reduced by heat-denaturation of peptides at 95 °C for 5 minutes in the presence of 0.1 M NaOH containing 1% (w/v) SDS, prior to incubation for 30 min at 37 °C in BCA standard working reagent. This modification to the standard bicinchoninic acid (BCA) assay protocol allows for an accurate, rapid and economical estimation of the peptide concentration within an unknown sample.