In practice, if you were to select a protein determination method to use for an
ID: 30873 • Letter: I
Question
In practice, if you were to select a protein determination method to use for an unknown sample, you would want to select one that would measure protein in a manner and range most appropriate to the sample that you have at hand. Discuss how you would measure protein in the following samples:
i) a small volume of sample that you are trying to keep for a future experiment and which has a protein concentration of around 0.05 mg/ml.
ii)lots of sample, and an approximate protein concentration of 10 mg/ml
iii) a sample which is turbid, with a protein concentration of around 1 mg/ml
iv) the protein in solution is known to be deficient in tyrosine.
Explanation / Answer
1)
The most accurate method of determining protein concentration is by acid hydrolysis followed by amino acid analysis. Most other methods are sensitive to the amino acid composition of the protein, and absolute concentrations cannot be obtained. The method is based on both the Biuret reaction, in which the peptide bonds of proteins react with copper under alkaline conditions to produce Cu+, which reacts with the Folin reagent, and the Folin