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Star Republic: Guide for Biologists

Estimation of protein concentration --- Bradford (II)

Edited by Chang Zhu
1. Make a Bradford solution:
Coomassie Blue G-250 100 mg
95% ethanol 50 ml
85% (w/v) phosphoric acid 100 ml
ddH2O 750 ml

2. Using a 96-well plate, add 0, 2, 4, 6, 10, 15 and 20 g of BSA (1 mg/ml) to 7 wells.

3. Add up to 20 l samples.

4. Add 40 l Bradford solution to wells containing BSA or samples.

5. Add ddH2O to bring the final volume to 200 l.

6. Read absorbance at 595 nm.

9. Make a standard curve using the BSA reading and estimate the protein concentration in the sample.

Note: Bradford assay will not be accurate for samples containing high concentration of detergent.