If a standard curve generated from known protein concentrations shows a drastic deviation from expected absorbance values for unknown samples, what could be a potential underlying cause?

A drastic deviation between a standard curve and the absorbance of unknown samples often means that something is interfering with the measurement, such as a contaminant or a change in the protein itself. If the unknown samples contain detergents, salts, or other additives that also absorb at the same wavelength, they will add extra light absorption that the standard curve does not account for. This interference can make the unknowns appear to have higher concentrations than they actually do. For example, if a protein sample is diluted in a buffer that contains 0. 1 % SDS, the SDS will absorb at 280 nm and raise the absorbance reading, causing the plotted point to lie far above the expected line.