Tested samples typically take less than five minutes to reach the indicative measures of nm absorbance concentration, making the Bradford assay both reliable and quick. The Bradford assay is appropriate for general use and is distinguished from many other assays for being less susceptible to interference by compounds such as sodium, potassium, and certain carbohydrates that exist in samples.
One note to remember is that sodium dodecyl sulfate SDS , while often used to extract proteins from cells, interferes with the assay, and thus should be handled carefully. When proteins that carry residue of SDS are used as samples in the Bradford assay, the Coomassie dye is either kept from binding due to the bondage of SDS to proteins, or the SDS associates with the green form of the dye, shifting the equilibrium and overrepresenting the absorption at nm regardless of true protein concentration.
The exact protein concentration can be determined due to interpolation from a standard curve made by measuring the absorbance of a dilution series of proteins with known concentrations within the response range of the Bradford assay.
Materials in a Bradford assay include the color reagent and a protein standard. Kits can come with either pre-diluted protein standards of a listed concentration for a faster and easier use, or a lyophilized protein standard sample and heavily concentrated reagent for experimenters to manipulate and create their own concentration reagents and standards.
A spectrophotometer with a maximum transmission at or around nm is needed for the assay in order to determine the exact concentration in the tested sample solution. The Bradford assay does not work with proteins of all sizes - a minimum of Daltons in mass is a requirement for detection and measurement of concentration. Additional constraints of the Bradford assay include that it is incompatible with surfactants, proteins with poor acid solubility, and is highly sensitive to basic and aromatic amino acids such as arginine, histidine, and lysine.
At G-Biosciences, we offer a selection of supplies for your Bradford assay needs. Browse through our products and then contact us with any questions or to place an order.
All protein assays are subject to interference by certain substances under some conditions. The Bradford protein assay is quite robust and is compatible with many compounds commonly found in protein preparations.
A standard Bradford protein assay kit is compatible with the following chemicals:. For membrane preparations that have been solubilized with detergents, depending on the type of detergent and the concentration, it may be necessary to dilute the sample to reduce the concentration. If a quick Bradford protein assay kit with a ready-to-use Bradford reagent is used, detergents that interfere will need to be at a lower concentration in the sample than in the standard assay due to the high sample-to-dye ratio.
Dilution may also be required in the presence of flavonoids and some basic buffers, as they can also interfere with Bradford protein assays. Bio-Rad Bradford protein assay kits include either of two different proteins, BSA or BGG, as standards to construct a standard curve for the relative quantitation of the proteins in the samples.
For most determinations of protein concentration, relative values are generally sufficient. If necessary, the accuracy of the standards can be increased by preparing the standard dilutions in the same buffer as the samples. Typically, seven concentrations of standards are prepared to cover the linear range of a Bradford protein assay, ranging from 0. The Bradford Protein Assay Minimizes Interference All protein assays are subject to interference by certain substances under some conditions.
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