Bio-Rad Quick Start™ Bradford Protein Assay - Manual (Page 5)

Work with synthetic polyamino acids indicates
that Coomassie Brilliant Blue G-250 dye binds
primarily to basic (especially arginine) and
aromatic amino acid residues (Compton and
Jones 1985). Spector (1978) found that the
extinction coefficient of a dye-albumin complex
solution was constant over a 10-fold concentra-
tion range. Thus, Beer's law may be applied for
accurate quantitation of protein by selecting an
appropriate ratio of dye volume to sample
concentration.
Certain chemical-protein and chemical-dye
interactions interfere with the assay. Interference
from non-protein compounds is due to their ability
to shift the equilibrium levels of the dye among the
three colored species. Known sources of interference,
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