Both Assays are biochemical assay used to determine the total concentration of protein in a solution
Bicinchoninic acid assay (BCA assay) is a Copper-based protein assays , which is also known as Smith assay. The total protein concentration is shown with a change in sample solution colour from green to purplish in proportion to protein concentration, which then measured using colorimetric techniques.
Some benefit compared to Bradford and Lowry assays is that BCA Protein Assay is compatible with samples that contain up to 5% surfactants / detergents. Also, BCA Assay responds more uniformly to different proteins compared to Bradford method.
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The Bradford assay, a colorimetric protein assay and dye-based Protein Assay Chemistries, is based on an absorbance shift of the dye Coomassie Brilliant Blue G-250 in which under acidic conditions the red form of the dye is converted into its bluer form to bind to the protein being assayed.
Compared to other assay, Bradford is fast and easy to perform since it is performed at room temperature and no special equipment is required. The This coomassie dyed based assays are compatible with most salts, solvents, buffers, thiols, reducing substances and metal chelating agents encountered in protein samples.
The main disadvantage of is their incompatibility with surfactants at concentrations routinely used to solubilize membrane proteins. The presence of a surfactant in the sample will causes precipitation of the reagent. Coomassie dye-based is highly acidic, therefore proteins with poor acid-solubility should be avoided. Finally, Bradford Assay result in about twice as much protein-to-protein variation as BCA Assay
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