This lab examines the relationship between the absorbance of light by a solution

Question

This lab examines the relationship between the absorbance of light by a solution at 595 nm and the concentration of the Coomassie Blue dye-BSA protein complex in the solution. State whether the following descriptions of the lab experiment are valid and explain why you say Yes or No: The experiment would be significantly more accurate if absorbance readings were recorded for a range of wavelengths, not just for 595 nm. The experiment has limited accuracy because it does not account for the absorbance of b. light by the other components (components that are not the dye-protein complex, such as excess dye that is not bound to any protein) of the solution. The absorbance reading measures practically all the protein content in the solutions. Melamine is an organic compound that can be easily mistaken for an amino acid because it contains the amine functional group, NH_2, however it is actually a tri-amine organic base that has a high nitrogen content due to its tri-amine structure. Protein tests that measure for overall nitrogen content do not distinguish between amino acids and melamine. In 2007, the addition of melamine to pet food led to a product recall in the US and Europe, and in 2008, the addition of melamine to milk and infant formula in China led to one of the largest food safety events in history. Describe the most likely reason for why company leaders would add melamine to their product to make the protein content appear higher than the actual amount in the product. Describe two possible reasons for why food safety inspectors often use an overall nitrogen content test, instead of a Bradford assay, to determine the protein content in a product.

Explanation / Answer

Solution.

1. a) Yes, the experiment would have more accuracy if absorbance readings were recorded for a range of wave lengths. Measuring absorbance precisely at the wavelength of an absorption peak, i.e. at max, in a hypothetical case of any wavelength setting within the narrow band would have no significant effect on absorbance measured at the peak. However, the same band of wavelengths displaced to shorter wavelength would introduce the possibility of major error, depending on the precise point within the band at which the measurement was taken. Errors due to either wavelength setting or instrument calibration will be at a minimum when measurements are made at the wavelength of maximum absorption.

b) Yes, the experiment may have limited accuracy in case of non-protein bound dye have the similar characteristic absorption frequency as that of bound dye-protein complex. In this case it would be difficult to account for the concentration of dye-protein complex alone.

c) Yes, in absence of any impurity and free dye in the sample solution, the absorbance readings can be accounted for all the dye-protein complex and eventually the concentration of protein using Beer-Lambert law.

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