The Bradford Assay

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What is the Bradford Assay?

The Bradford Protein Assay is a simple spectroscopic technique which is used in laboratory research to measure the total concentration of protein in a particular sample. 
The principle of the procedure revolves around the concept that the maximum absorbance of acidic Coomassie Brilliant Blue G-250 alters when protein binding occurs. The anionic state of the reagent is stabilised through ionic and hydrophobic interactions, resulting in a noticeable colour change. 
Consequently, the Bradford Protein Assay is often a vital step of sample preparation before comprehensive SDS-PAGE and Western Blot analysis in antibody research. Technical factors such as loading time, cuvette material and dye temperature can all affect the results which are drawn from the process.

Is there a way to optimise when loading multiple samples?

The use of an 8-channel pipettor is recommended when loading multiple samples, in order to reduce sample evaporation as a result of loading delays. By extension, we also recommend diminishing evaporation and increasing the accuracy of results by reducing any delays between loading the sample and taking measurements. 
In all Bradford Protein Assays, it is vital to suitably load the cuvettes with enough sample solution to ensure that the light path is transecting the meniscus.

Can you use this assay for all proteins?

No, this particular assay is only useful in the detection and quantification of proteins which are at least 3000 Daltons in mass. Therefore, you may wish to reconsider using this particular technique with smaller proteins, where methods such as the Bicinchoninic Acid Assay may be more appropriate.