b'Protein quantitation productsProtein assaysAccurately quantifying total protein concentration is a key step in most experiments and workflows involving isolation, separation, and analysis of proteins by biochemical methods. Depending on the accuracy required and the amount and purity of the protein available, different methods are appropriate for determining protein concentration. Colorimetric and fluorescent reagent-based protein assay techniques are available. Protein is added to the reagent, producing a color change or fluorescent readout in proportion to the amount added. A standard curve consisting of known concentrations of a purified protein is used to determine protein concentration. Because of the diversity of protein samples, careful consideration should be given to the choice of assay.Important criteria for choosing an assay include:Compatibility with the sample type and buffer componentsAssay working range and required sample volumeProtein-to-protein uniformitySpeed and convenience for the number of samples to be testedAvailability of necessary equipment to measure the assay outputMultiple formulations for flexible and accurate quantitationWe offer numerous colorimetric and fluorescent assays for detection and quantitation of total protein to meet the sensitivity and compatibility requirements of your samples (Table 9). In addition, we offer easy-to-use colorimetric or fluorescent peptide assays that are designed specifically to improve the sensitivity and reproducibility of peptide mixture quantitation.Table 9. Protein assay guide.Thermo ScientificThermo ScientificThermo ScientificInvitrogen InvitrogenPierce Rapid GoldPierce BCA ProteinPierce Coomassie PlusQubit Protein BRNanoOrange Protein BCA Protein Assay Kit Assay Kit (Bradford) Assay Kit Assay Kit Quantitation Assay5 min room temperatureDetergent-compatibleReducing-agent compatible,Rapid quantitation forBest for dilute samples or Assay highlightsBCA assay assay with linear curverapid assay broad range of proteinsamples with limited volumeand high accuracy concentrationsMinimum sample10 L 25 L 10 L 10 L 1 LvolumeWorking range 1252,000 g/mL 202,000 g/mL 1001,500 g/mL 10020,000 g/mL 0.0110 g/mL Compatibility Detergents DetergentsReducing agents Detergents and reducingReducing agentsagentsIncubationRT 37C RT RT 9095CtemperatureAssay incubation5 min 30 min 5 min 10 min 10 mintimeAssay wavelength 480 nm 562 nm 595 nm 470/570 nm 470/570 nmRequiredSpectrophotometer orSpectrophotometer orSpectrophotometer orFluorometer or fluorescence equipment absorbance microplateabsorbance microplateabsorbance microplateQubit 4 Fluorometer microplate readerreader reader readerFor a full list of available protein concentration assays, visit thermofisher.com/proteinassaysProtein sample preparation thermofisher.com/proteinbiology 23'