For workflows utilizing in-solution digestion protocols, it is critical to measure protein concentration following sample lysis using a standard protein assay in order to optimize the ratio of sample/protease (w/w) for digestion. It is also necessary to measure protein/peptide concentration upstream of isobaric labeling to ensure that equal amounts of sample are labeled before mixing. Since most protein assays are not sensitive enough to measure peptide concentration after digestion, the easy-to-use Pierce Colorimetric or Fluorescent peptide assays have been designed specifically to improve the sensitivity and reproducibility of quantitation of peptide mixtures.

  • Specific—optimized assays for peptide concentration measurements
  • Optimized—both assays designed for maximum sensitivity, accuracy and reproducibility
  • Convenient—simple protocols with a representative standard included in kit
  • Validated—all products have been fully tested and processed samples have been analyzed using Thermo Scientific™ Mass Spectrometers

Choose the right quantitation assay for your application

  Colorimetric Peptide Assay Fluorometric Peptide Assay
Recommended sample type Peptide Peptide
Measurement Colorimetric (480 nm) Fluorescent (Ex. 390, Em. 475 nm)
Linear range 15-1000 µg/mL 5-1000 µg/mL
Sensitivity 15 µg/mL 5 µg/mL
Minimum sample volume required 20 µL 10 µL
Amount detected at minimum sample volume 300 ng peptide 50 ng peptide
Assay time 30 min 5 min
Key feature Recommended for TMT-labeled peptides Recommended for single peptides
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The BCA Protein Assay become a popular method for colorimetric detection and quantitation of total protein has a unique advantage over other protein assays because of its compatibility with samples that contain up to 5% surfactants (detergents). Compared to most dye-binding methods, the BCA Assay is affected much less by protein compositional differences, providing greater protein-to-protein uniformity.