The absorbance values of the standard protein are plotted against the amount of the protein added for the assay. The curve is fit using linear regression with intercept (0,0) as shown in figure 5.2.
Figure 5.2: Plot of absorbance at 595 nm against the amount of protein
The equation of this regression line is: Absorbance = 0.00402 × amount of protein
Now, let us calculate the concentration of the unknown protein. We have got absorbance at different dilutions but which one should be used for determining the concentration. The absorbance values lying between 0.05 – 0.6 are most reliable. We shall, therefore, calculate the concentration for the 10-fold diluted sample that gave an absorbance of 0.426. The amount of protein is given by:
As this amount of the protein was present in the 100 μl of the 10-fold diluted protein sample, the concentration of the given protein sample 